cmdx.py

# -*- coding: utf-8 -*-

import os
import sys
import json
import time
import math
import types
import logging
import traceback
import operator
import collections
from functools import wraps

from maya import cmds
from maya.api import OpenMaya as om, OpenMayaAnim as oma, OpenMayaUI as omui
from maya import OpenMaya as om1, OpenMayaMPx as ompx1, OpenMayaUI as omui1

__version__ = "0.4.0"

PY3 = sys.version_info[0] == 3

# Bypass assertion error on unsupported Maya versions
IGNORE_VERSION = bool(os.getenv("CMDX_IGNORE_VERSION"))

# Output profiling information to console
# CAREFUL! This will flood your console. Use sparingly.
TIMINGS = bool(os.getenv("CMDX_TIMINGS"))

# Do not perform any caching of nodes or plugs
SAFE_MODE = bool(os.getenv("CMDX_SAFE_MODE"))

# Increase performance by not protecting against
# fatal crashes (e.g. operations on deleted nodes)
# This can be useful when you know for certain that a
# series of operations will happen in isolation, such
# as during an auto rigging build or export process.
ROGUE_MODE = not SAFE_MODE and bool(os.getenv("CMDX_ROGUE_MODE"))

# Increase performance by not bothering to free up unused memory
MEMORY_HOG_MODE = not SAFE_MODE and bool(os.getenv("CMDX_MEMORY_HOG_MODE"))

ENABLE_PEP8 = True

# Support undo/redo
ENABLE_UNDO = not SAFE_MODE

# Required
ENABLE_NODE_REUSE = True
ENABLE_PLUG_REUSE = True

if PY3:
    string_types = str,
else:
    string_types = str, basestring, unicode

try:
    __maya_version__ = int(cmds.about(version=True))
except (AttributeError, ValueError):
    __maya_version__ = 2015  # E.g. Preview Release 95

if not IGNORE_VERSION:
    assert __maya_version__ >= 2015, "Requires Maya 2015 or newer"

self = sys.modules[__name__]
self.installed = False
log = logging.getLogger("cmdx")

# Aliases - API 1.0
om1 = om1
omui1 = omui1

# Aliases - API 2.0
om = om
oma = oma
omui = omui

# Accessible via `cmdx.NodeReuseCount` etc.
Stats = self
Stats.NodeInitCount = 0
Stats.NodeReuseCount = 0
Stats.PlugReuseCount = 0
Stats.LastTiming = None

# Node reuse depends on this member
if ENABLE_NODE_REUSE and not hasattr(om, "MObjectHandle"):
    log.warning("Disabling node reuse (OpenMaya.MObjectHandle not found)")
    ENABLE_NODE_REUSE = False

TimeUnit = om.MTime.uiUnit()

# DEPRECATED
MTime = om.MTime
MDistance = om.MDistance
MAngle = om.MAngle

TimeType = om.MTime
DistanceType = om.MDistance
AngleType = om.MAngle

ExistError = type("ExistError", (RuntimeError,), {})
DoNothing = None

# Reusable objects, for performance
GlobalDagNode = om.MFnDagNode()
GlobalDependencyNode = om.MFnDependencyNode()

First = 0
Last = -1

# Animation curve interpolation, from MFnAnimCurve::TangentType
Stepped = 5
Linear = 2
Smooth = 4

history = dict()


class ModifierError(RuntimeError):
    def __init__(self, history):
        tasklist = list()
        for task in history:
            cmd, args, kwargs = task
            tasklist += [
                "%s(%s)" % (cmd, ", ".join(map(repr, args)))
            ]

        message = (
            "An unexpected internal failure occurred, "
            "these tasks were attempted:\n- " +
            "\n- ".join(tasklist)
        )

        self.history = history
        super(ModifierError, self).__init__(message)


def withTiming(text="{func}() {time:.2f} ns"):
    """Append timing information to a function

    Example:
        @withTiming()
        def function():
            pass

    """

    def timings_decorator(func):
        if not TIMINGS:
            # Do not wrap the function.
            # This yields zero cost to runtime performance
            return func

        @wraps(func)
        def func_wrapper(*args, **kwargs):
            t0 = time.clock()

            try:
                return func(*args, **kwargs)
            finally:
                t1 = time.clock()
                duration = (t1 - t0) * 10 ** 6  # microseconds

                Stats.LastTiming = duration

                log.debug(
                    text.format(func=func.__name__,
                                time=duration)
                )

        return func_wrapper
    return timings_decorator


def protected(func):
    """Prevent fatal crashes from illegal access to deleted nodes"""
    if ROGUE_MODE:
        return func

    @wraps(func)
    def func_wrapper(*args, **kwargs):
        if args[0]._destroyed:
            raise ExistError("Cannot perform operation on deleted node")
        return func(*args, **kwargs)

    return func_wrapper


class _Type(int):
    """Facilitate use of isinstance(space, _Type)"""


MFn = om.MFn
kDagNode = _Type(om.MFn.kDagNode)
kShape = _Type(om.MFn.kShape)
kTransform = _Type(om.MFn.kTransform)
kJoint = _Type(om.MFn.kJoint)
kSet = _Type(om.MFn.kSet)


class _Space(int):
    """Facilitate use of isinstance(space, _Space)"""


# Spaces
sWorld = _Space(om.MSpace.kWorld)
sObject = _Space(om.MSpace.kObject)
sTransform = _Space(om.MSpace.kTransform)
sPostTransform = _Space(om.MSpace.kPostTransform)
sPreTransform = _Space(om.MSpace.kPreTransform)

kXYZ = om.MEulerRotation.kXYZ
kYZX = om.MEulerRotation.kYZX
kZXY = om.MEulerRotation.kZXY
kXZY = om.MEulerRotation.kXZY
kYXZ = om.MEulerRotation.kYXZ
kZYX = om.MEulerRotation.kZYX


class _Unit(int):
    """A Maya unit, for unit-attributes such as Angle and Distance

    Because the resulting classes are subclasses of `int`, there
    is virtually no run-time performance penalty to using it as
    an integer. No additional Python is called, most notably when
    passing the integer class to the Maya C++ binding (which wouldn't
    call our overridden methods anyway).

    The added overhead to import time is neglible.

    """

    def __new__(cls, unit, enum):
        self = super(_Unit, cls).__new__(cls, enum)
        self._unit = unit
        return self

    def __call__(self, enum):
        return self._unit(enum, self)


# Angular units
Degrees = _Unit(om.MAngle, om.MAngle.kDegrees)
Radians = _Unit(om.MAngle, om.MAngle.kRadians)
AngularMinutes = _Unit(om.MAngle, om.MAngle.kAngMinutes)
AngularSeconds = _Unit(om.MAngle, om.MAngle.kAngSeconds)

# Distance units
Millimeters = _Unit(om.MDistance, om.MDistance.kMillimeters)
Centimeters = _Unit(om.MDistance, om.MDistance.kCentimeters)
Meters = _Unit(om.MDistance, om.MDistance.kMeters)
Kilometers = _Unit(om.MDistance, om.MDistance.kKilometers)
Inches = _Unit(om.MDistance, om.MDistance.kInches)
Feet = _Unit(om.MDistance, om.MDistance.kFeet)
Miles = _Unit(om.MDistance, om.MDistance.kMiles)
Yards = _Unit(om.MDistance, om.MDistance.kYards)

_Cached = type("Cached", (object,), {})  # For isinstance(x, _Cached)
Cached = _Cached()

_data = collections.defaultdict(dict)


class Singleton(type):
    """Re-use previous instances of Node

    Cost: 14 microseconds

    This enables persistent state of each node, even when
    a node is discovered at a later time, such as via
    :func:`DagNode.parent()` or :func:`DagNode.descendents()`

    Arguments:
        mobject (MObject): Maya API object to wrap
        exists (bool, optional): Whether or not to search for
            an existing Python instance of this node

    Example:
        >>> nodeA = createNode("transform", name="myNode")
        >>> nodeB = createNode("transform", parent=nodeA)
        >>> encode("|myNode") is nodeA
        True
        >>> nodeB.parent() is nodeA
        True

    """

    _instances = {}

    @withTiming()
    def __call__(cls, mobject, exists=True, modifier=None):
        handle = om.MObjectHandle(mobject)
        hsh = handle.hashCode()
        hx = "%x" % hsh

        if exists and handle.isValid():
            try:
                node = cls._instances[hx]
                assert not node._destroyed
            except (KeyError, AssertionError):
                pass
            else:
                Stats.NodeReuseCount += 1
                node._removed = False
                return node

        # It didn't exist, let's create one
        # But first, make sure we instantiate the right type
        if mobject.hasFn(om.MFn.kDagNode):
            sup = DagNode
        elif mobject.hasFn(om.MFn.kSet):
            sup = ObjectSet
        elif mobject.hasFn(om.MFn.kAnimCurve):
            sup = AnimCurve
        else:
            sup = Node

        self = super(Singleton, sup).__call__(mobject, exists, modifier)
        self._hashCode = hsh
        self._hexStr = hx
        cls._instances[hx] = self
        return self


class Node(object):
    """A Maya dependency node

    Example:
        >>> _ = cmds.file(new=True, force=True)
        >>> decompose = createNode("decomposeMatrix", name="decompose")
        >>> str(decompose)
        'decompose'
        >>> alias = encode(decompose.name())
        >>> decompose == alias
        True
        >>> transform = createNode("transform")
        >>> transform["tx"] = 5
        >>> transform["worldMatrix"][0] >> decompose["inputMatrix"]
        >>> decompose["outputTranslate"]
        (5.0, 0.0, 0.0)

    """

    if ENABLE_NODE_REUSE:
        __metaclass__ = Singleton

    _Fn = om.MFnDependencyNode

    # Module-level cache of previously created instances of Node
    _Cache = dict()

    def __eq__(self, other):
        """MObject supports this operator explicitly"""
        try:
            # Better to ask forgivness than permission
            return self._mobject == other._mobject
        except AttributeError:
            return str(self) == str(other)

    def __ne__(self, other):
        try:
            return self._mobject != other._mobject
        except AttributeError:
            return str(self) != str(other)

    def __str__(self):
        return self.name(namespace=True)

    def __repr__(self):
        return self.name(namespace=True)

    def __add__(self, other):
        """Support legacy + '.attr' behavior

        Example:
            >>> node = createNode("transform")
            >>> getAttr(node + ".tx")
            0.0
            >>> delete(node)

        """

        return self[other.strip(".")]

    def __contains__(self, other):
        """Does the attribute `other` exist?"""

        return self.hasAttr(other)

    def __getitem__(self, key):
        """Get plug from self

        Arguments:
            key (str, tuple): String lookup of attribute,
                optionally pass tuple to include unit.

        Example:
            >>> node = createNode("transform")
            >>> node["translate"] = (1, 1, 1)
            >>> node["translate", Meters]
            (0.01, 0.01, 0.01)

        """

        unit = None
        cached = False
        if isinstance(key, (list, tuple)):
            key, items = key[0], key[1:]

            for item in items:
                if isinstance(item, _Unit):
                    unit = item
                elif isinstance(item, _Cached):
                    cached = True

        if cached:
            try:
                return CachedPlug(self._state["values"][key, unit])
            except KeyError:
                pass

        try:
            plug = self.findPlug(key)
        except RuntimeError:
            raise ExistError("%s.%s" % (self.path(), key))

        return Plug(self, plug, unit=unit, key=key, modifier=self._modifier)

    def __setitem__(self, key, value):
        """Support item assignment of new attributes or values

        Example:
            >>> _ = cmds.file(new=True, force=True)
            >>> node = createNode("transform", name="myNode")
            >>> node["myAttr"] = Double(default=1.0)
            >>> node["myAttr"] == 1.0
            True
            >>> node["rotateX", Degrees] = 1.0
            >>> node["rotateX"] = Degrees(1)
            >>> node["rotateX", Degrees]
            1.0
            >>> node["myDist"] = Distance()
            >>> node["myDist"] = node["translateX"]
            >>> node["myDist", Centimeters] = node["translateX", Meters]
            >>> round(node["rotateX", Radians], 3)
            0.017
            >>> node["myDist"] = Distance()
            Traceback (most recent call last):
            ...
            ExistError: myDist
            >>> node["notExist"] = 5
            Traceback (most recent call last):
            ...
            ExistError: |myNode.notExist
            >>> delete(node)

        """

        if isinstance(value, Plug):
            value = value.read()

        unit = None
        if isinstance(key, (list, tuple)):
            key, unit = key

            # Convert value to the given unit
            if isinstance(value, (list, tuple)):
                value = list(unit(v) for v in value)
            else:
                value = unit(value)

        # Create a new attribute
        elif isinstance(value, (tuple, list)):
            if isinstance(value[0], type):
                if issubclass(value[0], _AbstractAttribute):
                    Attribute, kwargs = value
                    attr = Attribute(key, **kwargs)

                    if isinstance(attr, Divider):
                        indent = "_"
                        while indent in self:
                            indent += "_"

                        attr["name"] = indent
                        attr["shortName"] = indent

                    try:
                        return self.addAttr(attr.create())

                    except RuntimeError:
                        # NOTE: I can't be sure this is the only occasion
                        # where this exception is thrown. Stay catious.
                        raise ExistError(key)

        try:
            plug = self.findPlug(key)
        except RuntimeError:
            raise ExistError("%s.%s" % (self.path(), key))

        plug = Plug(self, plug, unit=unit)

        if not getattr(self._modifier, "isDone", True):

            # Only a few attribute types are supported by a modifier
            if _python_to_mod(value, plug, self._modifier._modifier):
                return
            else:
                log.warning(
                    "Could not write %s via modifier, writing directly.."
                    % plug
                )

        # Else, write it immediately
        plug.write(value)

    def _onDestroyed(self, mobject):
        self._destroyed = True

        om.MMessage.removeCallbacks(self._state["callbacks"])

        for callback in self.onDestroyed:
            try:
                callback(self)
            except Exception:
                traceback.print_exc()

        _data.pop(self.hex, None)

    def _onRemoved(self, mobject, modifier, _=None):
        self._removed = True

        for callback in self.onRemoved:
            try:
                callback()
            except Exception:
                traceback.print_exc()

    def __delitem__(self, key):
        self.deleteAttr(key)

    @withTiming()
    def __init__(self, mobject, exists=True, modifier=None):
        """Initialise Node

        Private members:
            mobject (om.MObject): Wrap this MObject
            fn (om.MFnDependencyNode): The corresponding function set
            modifier (om.MDagModifier, optional): Operations are
                deferred to this modifier.
            destroyed (bool): Has this node been destroyed by Maya?
            state (dict): Optional state for performance

        """

        self._mobject = mobject
        self._fn = self._Fn(mobject)
        self._modifier = modifier
        self._destroyed = False
        self._removed = False
        self._hashCode = None
        self._state = {
            "plugs": dict(),
            "values": dict(),
            "callbacks": list()
        }

        # Callbacks
        self.onDestroyed = list()
        self.onRemoved = list()

        Stats.NodeInitCount += 1

        self._state["callbacks"] += [
            # Monitor node deletion, to prevent accidental
            # use of MObject past its lifetime which may
            # result in a fatal crash.
            om.MNodeMessage.addNodeDestroyedCallback(
                mobject,
                self._onDestroyed,  # func
                None  # clientData
            ) if not ROGUE_MODE else 0,

            om.MNodeMessage.addNodeAboutToDeleteCallback(
                mobject,
                self._onRemoved,
                None
            ),
        ]

    def plugin(self):
        """Return the user-defined class of the plug-in behind this node"""
        return type(self._fn.userNode())

    def instance(self):
        """Return the current plug-in instance of this node"""
        return self._fn.userNode()

    def object(self):
        """Return MObject of this node"""
        return self._mobject

    def isAlive(self):
        """The node exists somewhere in memory"""
        return not self._destroyed

    @property
    def data(self):
        """Special handling for data stored in the instance

        Normally, the initialisation of data could happen in the __init__,
        but for some reason the postConstructor of a custom plug-in calls
        __init__ twice for every unique hex, which causes any data added
        there to be wiped out once the postConstructor is done.

        """

        return _data[self.hex]

    @property
    def destroyed(self):
        return self._destroyed

    @property
    def exists(self):
        """The node exists in both memory *and* scene

        Example:
            >>> node = createNode("joint")
            >>> node.exists
            True
            >>> cmds.delete(str(node))
            >>> node.exists
            False
            >>> node.destroyed
            False
            >>> _ = cmds.file(new=True, force=True)
            >>> node.exists
            False
            >>> node.destroyed
            True

        """

        return not self._removed

    @property
    def removed(self):
        return self._removed

    @property
    def hashCode(self):
        """Return MObjectHandle.hashCode of this node

        This a guaranteed-unique integer (long in Python 2)
        similar to the UUID of Maya 2016

        """

        return self._hashCode

    @property
    def hexStr(self):
        """Return unique hashCode as hexadecimal string

        Example:
            >>> node = createNode("transform")
            >>> node.hexStr == format(node.hashCode, "x")
            True

        """

        return self._hexStr

    # Alias
    code = hashCode
    hex = hexStr

    @property
    def typeId(self):
        """Return the native maya.api.MTypeId of this node

        Example:
            >>> node = createNode("transform")
            >>> node.typeId == tTransform
            True

        """

        return self._fn.typeId

    @property
    def typeName(self):
        return self._fn.typeName

    def isA(self, type):
        """Evaluate whether self is of `type`

        Arguments:
            type (int): MFn function set constant

        Example:
            >>> node = createNode("transform")
            >>> node.isA(kTransform)
            True
            >>> node.isA(kShape)
            False

        """

        return self._mobject.hasFn(type)

    def lock(self, value=True):
        self._fn.isLocked = value

    def isLocked(self):
        return self._fn.isLocked

    @property
    def storable(self):
        """Whether or not to save this node with the file"""

        # How is this value queried?
        return None

    @storable.setter
    def storable(self, value):

        # The original function is a double negative
        self._fn.setDoNotWrite(not bool(value))

    # Module-level branch; evaluated on import
    if ENABLE_PLUG_REUSE:
        @withTiming("findPlug() reuse {time:.4f} ns")
        def findPlug(self, name, cached=False):
            """Cache previously found plugs, for performance

            Cost: 4.9 microseconds/call

            Part of the time taken in querying an attribute is the
            act of finding a plug given its name as a string.

            This causes a 25% reduction in time taken for repeated
            attribute queries. Though keep in mind that state is stored
            in the `cmdx` object which currently does not survive rediscovery.
            That is, if a node is created and later discovered through a call
            to `encode`, then the original and discovered nodes carry one
            state each.

            Additional challenges include storing the same plug for both
            long and short name of said attribute, which is currently not
            the case.

            Arguments:
                name (str): Name of plug to find
                cached (bool, optional): Return cached plug, or
                    throw an exception. Default to False, which
                    means it will run Maya's findPlug() and cache
                    the result.
                safe (bool, optional): Always find the plug through
                    Maya's API, defaults to False. This will not perform
                    any caching and is intended for use during debugging
                    to spot whether caching is causing trouble.

            Example:
                >>> node = createNode("transform")
                >>> node.findPlug("translateX", cached=True)
                Traceback (most recent call last):
                ...
                KeyError: "'translateX' not cached"
                >>> plug1 = node.findPlug("translateX")
                >>> isinstance(plug1, om.MPlug)
                True
                >>> plug1 is node.findPlug("translateX")
                True
                >>> plug1 is node.findPlug("translateX", cached=True)
                True

            """

            try:
                existing = self._state["plugs"][name]
                Stats.PlugReuseCount += 1
                return existing
            except KeyError:
                if cached:
                    raise KeyError("'%s' not cached" % name)

            plug = self._fn.findPlug(name, False)
            self._state["plugs"][name] = plug

            return plug

    else:
        @withTiming("findPlug() no reuse {time:.4f} ns")
        def findPlug(self, name):
            """Always lookup plug by name

            Cost: 27.7 microseconds/call

            """

            return self._fn.findPlug(name, False)

    def update(self, attrs):
        """Apply a series of attributes all at once

        This operates similar to a Python dictionary.

        Arguments:
            attrs (dict): Key/value pairs of name and attribute

        Examples:
            >>> node = createNode("transform")
            >>> node.update({"tx": 5.0, ("ry", Degrees): 30.0})
            >>> node["tx"]
            5.0

        """

        for key, value in attrs.items():
            self[key] = value

    def clear(self):
        """Clear transient state

        A node may cache previously queried values for performance
        at the expense of memory. This method erases any cached
        values, freeing up memory at the expense of performance.

        Example:
            >>> node = createNode("transform")
            >>> node["translateX"] = 5
            >>> node["translateX"]
            5.0
            >>> # Plug was reused
            >>> node["translateX"]
            5.0
            >>> # Value was reused
            >>> node.clear()
            >>> node["translateX"]
            5.0
            >>> # Plug and value was recomputed

        """

        self._state["plugs"].clear()
        self._state["values"].clear()

    @protected
    def name(self, namespace=False):
        """Return the name of this node

        Arguments:
            namespace (bool, optional): Return with namespace,
                defaults to False

        Example:
            >>> node = createNode("transform", name="myName")
            >>> node.name()
            u'myName'

        """

        if namespace:
            return self._fn.name()
        else:
            return self._fn.name().rsplit(":", 1)[-1]

    def namespace(self):
        """Get namespace of node

        Example:
            >>> _ = cmds.file(new=True, force=True)
            >>> node = createNode("transform", name="myNode")
            >>> node.namespace()
            u''
            >>> _ = cmds.namespace(add=":A")
            >>> _ = cmds.namespace(add=":A:B")
            >>> node = createNode("transform", name=":A:B:myNode")
            >>> node.namespace()
            u'A:B'

        """

        name = self._fn.name()

        if ":" in name:
            # Else it will return name as-is, as namespace
            # E.g. Ryan_:leftHand -> Ryan_, but :leftHand -> leftHand
            return name.rsplit(":", 1)[0]

        return type(name)()

    # Alias
    def path(self):
        return self.name(namespace=True)

    shortestPath = path

    def pop(self, key):
        """Delete an attribute

        Arguments:
            key (str): Name of attribute to delete

        Example:
            >>> node = createNode("transform")
            >>> node["myAttr"] = Double()
            >>> node.pop("myAttr")
            >>> node.hasAttr("myAttr")
            False

        """

        del self[key]

    def dump(self, ignore_error=True):
        """Return dictionary of all attributes

        Example:
            >>> import json
            >>> _ = cmds.file(new=True, force=True)
            >>> node = createNode("choice")
            >>> dump = node.dump()
            >>> isinstance(dump, dict)
            True
            >>> dump["choice1.caching"]
            False

        """

        attrs = {}
        count = self._fn.attributeCount()
        for index in range(count):
            obj = self._fn.attribute(index)
            plug = self._fn.findPlug(obj, False)

            try:
                value = Plug(self, plug).read()
            except (RuntimeError, TypeError):
                # TODO: Support more types of attributes,
                # such that this doesn't need to happen.
                value = None

                if not ignore_error:
                    raise

            attrs[plug.name()] = value

        return attrs

    def dumps(self, indent=4, sortKeys=True):
        """Return a JSON compatible dictionary of all attributes"""
        return json.dumps(self.dump(), indent=indent, sort_keys=sortKeys)

    def type(self):
        """Return type name

        Example:
            >>> node = createNode("choice")
            >>> node.type()
            u'choice'

        """

        return self._fn.typeName

    def addAttr(self, attr):
        """Add a new dynamic attribute to node

        Arguments:
            attr (Plug): Add this attribute

        Example:
            >>> node = createNode("transform")
            >>> attr = Double("myAttr", default=5.0)
            >>> node.addAttr(attr)
            >>> node["myAttr"] == 5.0
            True

        """

        if isinstance(attr, _AbstractAttribute):
            attr = attr.create()

        self._fn.addAttribute(attr)

    def hasAttr(self, attr):
        """Return whether or not `attr` exists

        Arguments:
            attr (str): Name of attribute to check

        Example:
            >>> node = createNode("transform")
            >>> node.hasAttr("mysteryAttribute")
            False
            >>> node.hasAttr("translateX")
            True
            >>> node["myAttr"] = Double()  # Dynamic attribute
            >>> node.hasAttr("myAttr")
            True

        """

        return self._fn.hasAttribute(attr)

    def deleteAttr(self, attr):
        """Delete `attr` from node

        Arguments:
            attr (Plug): Attribute to remove

        Example:
            >>> node = createNode("transform")
            >>> node["myAttr"] = Double()
            >>> node.deleteAttr("myAttr")
            >>> node.hasAttr("myAttr")
            False

        """

        if not isinstance(attr, Plug):
            attr = self[attr]

        attribute = attr._mplug.attribute()
        self._fn.removeAttribute(attribute)

    def connections(self, type=None, unit=None, plugs=False):
        """Yield plugs of node with a connection to any other plug

        Arguments:
            unit (int, optional): Return plug in this unit,
                e.g. Meters or Radians
            type (str, optional): Restrict output to nodes of this type,
                e.g. "transform" or "mesh"
            plugs (bool, optional): Return plugs, rather than nodes

        Example:
            >>> _ = cmds.file(new=True, force=True)
            >>> a = createNode("transform", name="A")
            >>> b = createNode("multDoubleLinear", name="B")
            >>> a["ihi"] << b["ihi"]
            >>> list(a.connections()) == [b]
            True
            >>> list(b.connections()) == [a]
            True
            >>> a.connection() == b
            True

        """

        for plug in self._fn.getConnections():
            mobject = plug.node()
            node = Node(mobject)

            if not type or type == node._fn.typeName:
                plug = Plug(node, plug, unit)
                for connection in plug.connections(plugs=plugs):
                    yield connection

    def connection(self, type=None, unit=None, plug=False):
        """Singular version of :func:`connections()`"""
        return next(self.connections(type, unit, plug), None)

    def rename(self, name):
        if not getattr(self._modifier, "isDone", True):
            return self._modifier.rename(self, name)

        mod = om.MDGModifier()
        mod.renameNode(self._mobject, name)
        mod.doIt()

    if ENABLE_PEP8:
        is_alive = isAlive
        hex_str = hexStr
        hash_code = hashCode
        type_id = typeId
        type_name = typeName
        is_a = isA
        is_locked = isLocked
        find_plug = findPlug
        add_attr = addAttr
        has_attr = hasAttr
        delete_attr = deleteAttr
        shortest_path = shortestPath


class DagNode(Node):
    """A Maya DAG node

    The difference between this and Node is that a DagNode
    can have one or more children and one parent (multiple
    parents not supported).

    Example:
        >>> _ = cmds.file(new=True, force=True)
        >>> parent = createNode("transform")
        >>> child = createNode("transform", parent=parent)
        >>> child.parent() == parent
        True
        >>> next(parent.children()) == child
        True
        >>> parent.child() == child
        True
        >>> sibling = createNode("transform", parent=parent)
        >>> child.sibling() == sibling
        True
        >>> shape = createNode("mesh", parent=child)
        >>> child.shape() == shape
        True
        >>> shape.parent() == child
        True

    """

    _Fn = om.MFnDagNode

    def __str__(self):
        return self.path()

    def __repr__(self):
        return self.path()

    def __init__(self, mobject, *args, **kwargs):
        super(DagNode, self).__init__(mobject, *args, **kwargs)

        self._tfn = om.MFnTransform(mobject)

    @protected
    def path(self):
        """Return full path to node

        Example:
            >>> parent = createNode("transform", "myParent")
            >>> child = createNode("transform", "myChild", parent=parent)
            >>> child.name()
            u'myChild'
            >>> child.path()
            u'|myParent|myChild'

        """

        return self._fn.fullPathName()

    @protected
    def dagPath(self):
        """Return a om.MDagPath for this node

        Example:
            >>> _ = cmds.file(new=True, force=True)
            >>> parent = createNode("transform", name="Parent")
            >>> child = createNode("transform", name="Child", parent=parent)
            >>> path = child.dagPath()
            >>> str(path)
            'Child'
            >>> str(path.pop())
            'Parent'

        """

        return om.MDagPath.getAPathTo(self._mobject)

    @protected
    def shortestPath(self):
        """Return shortest unique path to node

        Example:
            >>> _ = cmds.file(new=True, force=True)
            >>> parent = createNode("transform", name="myParent")
            >>> child = createNode("transform", name="myChild", parent=parent)
            >>> child.shortestPath()
            u'myChild'
            >>> child = createNode("transform", name="myChild")
            >>> # Now `myChild` could refer to more than a single node
            >>> child.shortestPath()
            u'|myChild'

        """

        return self._fn.partialPathName()

    @property
    def level(self):
        """Return the number of parents this DAG node has

        Example:
            >>> parent = createNode("transform")
            >>> child = createNode("transform", parent=parent)
            >>> child.level
            1
            >>> parent.level
            0

        """

        return self.path().count("|") - 1

    def hide(self):
        """Set visibility to False"""
        self["visibility"] = False

    def show(self):
        """Set visibility to True"""
        self["visibility"] = True

    def addChild(self, child, index=Last):
        """Add `child` to self

        Arguments:
            child (Node): Child to add
            index (int, optional): Physical location in hierarchy,
                defaults to cmdx.Last

        Example:
            >>> parent = createNode("transform")
            >>> child = createNode("transform")
            >>> parent.addChild(child)

        """

        mobject = child._mobject
        self._fn.addChild(mobject, index)

    def assembly(self):
        """Return the top-level parent of node

        Example:
            >>> parent1 = createNode("transform")
            >>> parent2 = createNode("transform")
            >>> child = createNode("transform", parent=parent1)
            >>> grandchild = createNode("transform", parent=child)
            >>> child.assembly() == parent1
            True
            >>> parent2.assembly() == parent2
            True

        """

        path = self._fn.getPath()

        root = None
        for level in range(path.length() - 1):
            root = path.pop()

        return self.__class__(root.node()) if root else self

    def transform(self, space=sObject, time=None):
        """Return TransformationMatrix"""
        plug = self["worldMatrix"][0] if space == sWorld else self["matrix"]
        return TransformationMatrix(plug.asMatrix(time))

    def mapFrom(self, other, time=None):
        """Return TransformationMatrix of `other` relative self

        Example:
            >>> a = createNode("transform")
            >>> b = createNode("transform")
            >>> a["translate"] = (0, 5, 0)
            >>> b["translate"] = (0, -5, 0)
            >>> delta = a.mapFrom(b)
            >>> delta.translation()[1]
            10.0
            >>> a = createNode("transform")
            >>> b = createNode("transform")
            >>> a["translate"] = (0, 5, 0)
            >>> b["translate"] = (0, -15, 0)
            >>> delta = a.mapFrom(b)
            >>> delta.translation()[1]
            20.0

        """

        a = self["worldMatrix"][0].asMatrix(time)
        b = other["worldInverseMatrix"][0].asMatrix(time)
        delta = a * b
        return TransformationMatrix(delta)

    def mapTo(self, other, time=None):
        """Return TransformationMatrix of self relative `other`

        See :func:`mapFrom` for examples.

        """

        return other.mapFrom(self, time)

    # Alias
    root = assembly

    def parent(self, type=None):
        """Return parent of node

        Arguments:
            type (str, optional): Return parent, only if it matches this type

        Example:
            >>> parent = createNode("transform")
            >>> child = createNode("transform", parent=parent)
            >>> child.parent() == parent
            True
            >>> not child.parent(type="camera")
            True
            >>> parent.parent()

        """

        mobject = self._fn.parent(0)

        if mobject.apiType() == om.MFn.kWorld:
            return

        cls = self.__class__

        if not type or type == self._fn.__class__(mobject).typeName:
            return cls(mobject)

    def children(self,
                 type=None,
                 filter=om.MFn.kTransform,
                 query=None,
                 contains=None):
        """Return children of node

        All returned children are transform nodes, as specified by the
        `filter` argument. For shapes, use the :func:`shapes` method.
        The `contains` argument only returns transform nodes containing
        a shape of the type provided.

        Arguments:
            type (str, optional): Return only children that match this type
            filter (int, optional): Return only children with this function set
            contains (str, optional): Child must have a shape of this type
            query (dict, optional): Limit output to nodes with these attributes

        Example:
            >>> _ = cmds.file(new=True, force=True)
            >>> a = createNode("transform", "a")
            >>> b = createNode("transform", "b", parent=a)
            >>> c = createNode("transform", "c", parent=a)
            >>> d = createNode("mesh", "d", parent=c)
            >>> list(a.children()) == [b, c]
            True
            >>> a.child() == b
            True
            >>> c.child(type="mesh")
            >>> c.child(type="mesh", filter=None) == d
            True
            >>> c.child(type=("mesh", "transform"), filter=None) == d
            True
            >>> a.child() == b
            True
            >>> a.child(contains="mesh") == c
            True
            >>> a.child(contains="nurbsCurve") is None
            True
            >>> b["myAttr"] = Double(default=5)
            >>> a.child(query=["myAttr"]) == b
            True
            >>> a.child(query=["noExist"]) is None
            True
            >>> a.child(query={"myAttr": 5}) == b
            True
            >>> a.child(query={"myAttr": 1}) is None
            True

        """

        # Shapes have no children
        if self.isA(kShape):
            return

        cls = DagNode
        Fn = self._fn.__class__
        op = operator.eq

        if isinstance(type, (tuple, list)):
            op = operator.contains

        other = "typeId" if isinstance(type, om.MTypeId) else "typeName"

        for index in range(self._fn.childCount()):
            try:
                mobject = self._fn.child(index)

            except RuntimeError:
                # TODO: Unsure of exactly when this happens
                log.warning(
                    "Child %d of %s not found, this is a bug" % (index, self)
                )
                raise

            if filter is not None and not mobject.hasFn(filter):
                continue

            if not type or op(type, getattr(Fn(mobject), other)):
                node = cls(mobject)

                if not contains or node.shape(type=contains):
                    if query is None:
                        yield node

                    elif isinstance(query, dict):
                        try:
                            if all(node[key] == value
                                   for key, value in query.items()):
                                yield node
                        except ExistError:
                            continue

                    else:
                        if all(key in node for key in query):
                            yield node

    def child(self,
              type=None,
              filter=om.MFn.kTransform,
              query=None,
              contains=None):
        return next(self.children(type, filter, query, contains), None)

    def shapes(self, type=None, query=None):
        return self.children(type, kShape, query)

    def shape(self, type=None):
        return next(self.shapes(type), None)

    def siblings(self, type=None, filter=om.MFn.kTransform):
        parent = self.parent()

        if parent is not None:
            for child in parent.children(type=type, filter=filter):
                if child != self:
                    yield child

    def sibling(self, type=None, filter=None):
        return next(self.siblings(type, filter), None)

    # Module-level expression; this isn't evaluated
    # at run-time, for that extra performance boost.
    if hasattr(om, "MItDag"):
        def descendents(self, type=None):
            """Faster and more efficient dependency graph traversal

            Requires Maya 2017+

            Example:
                >>> grandparent = createNode("transform")
                >>> parent = createNode("transform", parent=grandparent)
                >>> child = createNode("transform", parent=parent)
                >>> mesh = createNode("mesh", parent=child)
                >>> it = grandparent.descendents(type=tMesh)
                >>> next(it) == mesh
                True
                >>> next(it)
                Traceback (most recent call last):
                ...
                StopIteration

            """

            type = type or om.MFn.kInvalid
            typeName = None

            # Support filtering by typeName
            if isinstance(type, string_types):
                typeName = type
                type = om.MFn.kInvalid

            it = om.MItDag(om.MItDag.kDepthFirst, om.MFn.kInvalid)
            it.reset(
                self._mobject,
                om.MItDag.kDepthFirst,
                om.MIteratorType.kMObject
            )

            it.next()  # Skip self

            while not it.isDone():
                mobj = it.currentItem()
                node = DagNode(mobj)

                if typeName is None:
                    if not type or type == node._fn.typeId:
                        yield node
                else:
                    if not typeName or typeName == node._fn.typeName:
                        yield node

                it.next()

    else:
        def descendents(self, type=None):
            """Recursive, depth-first search; compliant with MItDag of 2017+

            Example:
                >>> grandparent = createNode("transform")
                >>> parent = createNode("transform", parent=grandparent)
                >>> child = createNode("transform", parent=parent)
                >>> mesh = createNode("mesh", parent=child)
                >>> it = grandparent.descendents(type=tMesh)
                >>> next(it) == mesh
                True
                >>> next(it)
                Traceback (most recent call last):
                ...
                StopIteration

            """

            def _descendents(node, children=None):
                children = children or list()
                children.append(node)
                for child in node.children(filter=None):
                    _descendents(child, children)

                return children

            # Support filtering by typeName
            typeName = None
            if isinstance(type, str):
                typeName = type
                type = om.MFn.kInvalid

            descendents = _descendents(self)[1:]  # Skip self

            for child in descendents:
                if typeName is None:
                    if not type or type == child._fn.typeId:
                        yield child
                else:
                    if not typeName or typeName == child._fn.typeName:
                        yield child

    def descendent(self, type=om.MFn.kInvalid):
        """Singular version of :func:`descendents()`

        A recursive, depth-first search.

        .. code-block:: python

            a
            |
            b---d
            |   |
            c   e

        Example:
            >>> _ = cmds.file(new=True, force=True)
            >>> a = createNode("transform", "a")
            >>> b = createNode("transform", "b", parent=a)
            >>> c = createNode("transform", "c", parent=b)
            >>> d = createNode("transform", "d", parent=b)
            >>> e = createNode("transform", "e", parent=d)
            >>> a.descendent() == a.child()
            True
            >>> list(a.descendents()) == [b, c, d, e]
            True
            >>> f = createNode("mesh", "f", parent=e)
            >>> list(a.descendents(type="mesh")) == [f]
            True

        """

        return next(self.descendents(type), None)

    def duplicate(self):
        """Return a duplicate of self"""
        return self.__class__(self._fn.duplicate())

    def clone(self, name=None, parent=None, worldspace=False):
        """Return a clone of self

        A "clone" assignes the .outMesh attribute of a mesh node
        to the `.inMesh` of the resulting clone.

        Supports:
            - mesh

        Arguments:
            name (str, optional): Name of newly created clone
            parent (DagNode, optional): Parent to newly cloned node
            worldspace (bool, optional): Translate output to worldspace

        """

        if self.isA(kShape) and self.typeName == "mesh":
            assert parent is not None, "mesh cloning requires parent argument"
            name or parent.name() + "Clone"

            with DagModifier() as mod:
                mesh = mod.createNode("mesh", name, parent)
                mesh["inMesh"] << self["outMesh"]

            return mesh

        else:
            raise TypeError("Unsupported clone target: %s" % self)

    def isLimited(self, typ):
        return self._tfn.isLimited(typ)

    def limitValue(self, typ):
        return self._tfn.limitValue(typ)

    def enableLimit(self, typ, state):
        return self._tfn.enableLimit(typ, state)

    def setLimit(self, typ, value):
        return self._tfn.setLimit(typ, value)

    if ENABLE_PEP8:
        shortest_path = shortestPath
        add_child = addChild
        dag_path = dagPath
        map_from = mapFrom
        map_to = mapTo
        is_limited = isLimited
        limit_value = limitValue
        set_limit = setLimit
        enable_limit = enableLimit


# MFnTransform Limit Types
kRotateMaxX = 13
kRotateMaxY = 15
kRotateMaxZ = 17
kRotateMinX = 12
kRotateMinY = 14
kRotateMinZ = 16
kScaleMaxX = 1
kScaleMaxY = 3
kScaleMaxZ = 5
kScaleMinX = 0
kScaleMinY = 2
kScaleMinZ = 4
kShearMaxXY = 7
kShearMaxXZ = 9
kShearMaxYZ = 11
kShearMinXY = 6
kShearMinXZ = 8
kShearMinYZ = 10
kTranslateMaxX = 19
kTranslateMaxY = 21
kTranslateMaxZ = 23
kTranslateMinX = 18
kTranslateMinY = 20
kTranslateMinZ = 22


class ObjectSet(Node):
    """Support set-type operations on Maya sets

    Caveats
        1. MFnSet was introduced in Maya 2016, this class backports
            that behaviour for Maya 2015 SP3

        2. Adding a DAG node as a DG node persists its function set
            such that when you query it, it'll return the name rather
            than the path.

            Therefore, when adding a node to an object set, it's important
            that it is added either a DAG or DG node depending on what it it.

            This class manages this automatically.

    """

    @protected
    def shortestPath(self):
        return self.name(namespace=True)

    def __iter__(self):
        for member in self.members():
            yield member

    def add(self, member):
        """Add single `member` to set

        Arguments:
            member (cmdx.Node): Node to add

        """

        return self.update([member])

    def remove(self, members):
        mobj = _encode1(self.name(namespace=True))
        selectionList = om1.MSelectionList()

        if not isinstance(members, (tuple, list)):
            selectionList.add(members.path())

        else:
            for member in members:
                selectionList.add(member.path())

        fn = om1.MFnSet(mobj)
        fn.removeMembers(selectionList)

    def update(self, members):
        """Add several `members` to set

        Arguments:
            members (list): Series of cmdx.Node instances

        """

        cmds.sets(list(map(str, members)), forceElement=self.path())

    def clear(self):
        """Remove all members from set"""
        mobj = _encode1(self.name(namespace=True))
        fn = om1.MFnSet(mobj)
        fn.clear()

    def sort(self, key=lambda o: (o.typeName, o.path())):
        """Sort members of set by `key`

        Arguments:
            key (lambda): See built-in `sorted(key)` for reference

        """

        members = sorted(
            self.members(),
            key=key
        )

        self.clear()
        self.update(members)

    def descendent(self, type=None):
        """Return the first descendent"""
        return next(self.descendents(type), None)

    def descendents(self, type=None):
        """Return hierarchy of objects in set"""
        for member in self.members(type=type):
            yield member

            try:
                for child in member.descendents(type=type):
                    yield child

            except AttributeError:
                continue

    def flatten(self, type=None):
        """Return members, converting nested object sets into its members

        Example:
            >>> from maya import cmds
            >>> _ = cmds.file(new=True, force=True)
            >>> a = cmds.createNode("transform", name="a")
            >>> b = cmds.createNode("transform", name="b")
            >>> c = cmds.createNode("transform", name="c")
            >>> cmds.select(a)
            >>> gc = cmds.sets([a], name="grandchild")
            >>> cc = cmds.sets([gc, b], name="child")
            >>> parent = cmds.sets([cc, c], name="parent")
            >>> mainset = encode(parent)
            >>> sorted(mainset.flatten(), key=lambda n: n.name())
            [|a, |b, |c]

        """

        members = set()

        def recurse(objset):
            for member in objset:
                if member.isA(om.MFn.kSet):
                    recurse(member)
                elif type is not None:
                    if type == member.typeName:
                        members.add(member)
                else:
                    members.add(member)

        recurse(self)

        return list(members)

    def member(self, type=None):
        """Return the first member"""

        return next(self.members(type), None)

    def members(self, type=None):
        op = operator.eq
        other = "typeId"

        if isinstance(type, string_types):
            other = "typeName"

        if isinstance(type, (tuple, list)):
            op = operator.contains

        for node in cmds.sets(self.name(namespace=True), query=True) or []:
            node = encode(node)

            if not type or op(type, getattr(node._fn, other)):
                yield node


class AnimCurve(Node):
    if __maya_version__ >= 2016:
        def __init__(self, mobj, exists=True, modifier=None):
            super(AnimCurve, self).__init__(mobj, exists, modifier)
            self._fna = oma.MFnAnimCurve(mobj)

        def key(self, time, value, interpolation=Linear):
            time = om.MTime(time, om.MTime.uiUnit())
            index = self._fna.find(time)

            if index:
                self._fna.setValue(index, value)
            else:
                self._fna.addKey(time, value, interpolation, interpolation)

        def keys(self, times, values, interpolation=Linear):
            times = map(lambda t: om.MTime(t, TimeUnit), times)

            try:
                self._fna.addKeys(times, values)

            except RuntimeError:
                # The error provided by Maya aren't very descriptive,
                # help a brother out by look for common problems.

                if not times:
                    log.error("No times were provided: %s" % str(times))

                if not values:
                    log.error("No values were provided: %s" % str(values))

                if len(values) != len(times):
                    log.error(
                        "Count mismatch; len(times)=%d, len(values)=%d" % (
                            len(times), len(values)
                        )
                    )

                raise


class Plug(object):
    def __abs__(self):
        """Return absolute value of plug

        Example:
            >>> node = createNode("transform")
            >>> node["tx"] = -10
            >>> abs(node["tx"])
            10.0

        """

        return abs(self.read())

    def __bool__(self):
        """if plug:

        Example:
            >>> node = createNode("transform")
            >>> node["tx"] = 10
            >>> if node["tx"]:
            ...   True
            ...
            True

        """

        return bool(self.read())

    # Python 3
    __nonzero__ = __bool__

    def __float__(self):
        """Return plug as floating point value

        Example:
            >>> node = createNode("transform")
            >>> float(node["visibility"])
            1.0

        """

        return float(self.read())

    def __int__(self):
        """Return plug as int

        Example:
            >>> node = createNode("transform")
            >>> int(node["visibility"])
            1

        """

        return int(self.read())

    def __eq__(self, other):
        """Compare plug to `other`

        Example:
            >>> node = createNode("transform")
            >>> node["visibility"] == True
            True
            >>> node["visibility"] == node["nodeState"]
            False
            >>> node["visibility"] != node["nodeState"]
            True

        """

        if isinstance(other, Plug):
            other = other.read()
        return self.read() == other

    def __ne__(self, other):
        if isinstance(other, Plug):
            other = other.read()
        return self.read() != other

    def __neg__(self):
        """Negate unary operator

        Example:
            >>> node = createNode("transform")
            >>> node["visibility"] = 1
            >>> -node["visibility"]
            -1

        """

        return -self.read()

    def __div__(self, other):
        """Python 2.x division

        Example:
            >>> node = createNode("transform")
            >>> node["tx"] = 5
            >>> node["ty"] = 2
            >>> node["tx"] / node["ty"]
            2.5

        """

        if isinstance(other, Plug):
            other = other.read()
        return self.read() / other

    def __truediv__(self, other):
        """Float division, e.g. self / other"""
        if isinstance(other, Plug):
            other = other.read()
        return self.read() / other

    def __add__(self, other):
        """Support legacy add string to plug

        Note:
            Adding to short name is faster, e.g. node["t"] + "x",
            than adding to longName, e.g. node["translate"] + "X"

        Example:
            >>> node = createNode("transform")
            >>> node["tx"] = 5
            >>> node["translate"] + "X"
            5.0
            >>> node["t"] + "x"
            5.0
            >>> try:
            ...   node["t"] + node["r"]
            ... except TypeError:
            ...   error = True
            ...
            >>> error
            True

        """

        if isinstance(other, str):
            try:
                # E.g. node["t"] + "x"
                return self._node[self.name() + other]
            except ExistError:
                # E.g. node["translate"] + "X"
                return self._node[self.name(long=True) + other]

        raise TypeError(
            "unsupported operand type(s) for +: 'Plug' and '%s'"
            % type(other)
        )

    def __iadd__(self, other):
        """Support += operator, for .append()

        Example:
            >>> node = createNode("transform")
            >>> node["myArray"] = Double(array=True)
            >>> node["myArray"].append(1.0)
            >>> node["myArray"].extend([2.0, 3.0])
            >>> node["myArray"] += 5.1
            >>> node["myArray"] += [1.1, 2.3, 999.0]
            >>> node["myArray"][0]
            1.0
            >>> node["myArray"][6]
            999.0
            >>> node["myArray"][-1]
            999.0

        """

        if isinstance(other, (tuple, list)):
            for entry in other:
                self.append(entry)
        else:
            self.append(other)

        return self

    def __str__(self):
        """Return value as str

        Example:
            >>> node = createNode("transform")
            >>> str(node["tx"])
            '0.0'

        """

        return str(self.read())

    def __repr__(self):
        return str(self.read())

    def __rshift__(self, other):
        """Support connecting attributes via A >> B"""
        self.connect(other)

    def __lshift__(self, other):
        """Support connecting attributes via A << B"""
        other.connect(self)

    def __floordiv__(self, other):
        """Disconnect attribute via A // B

        Example:
            >>> nodeA = createNode("transform")
            >>> nodeB = createNode("transform")
            >>> nodeA["tx"] >> nodeB["tx"]
            >>> nodeA["tx"] = 5
            >>> nodeB["tx"] == 5
            True
            >>> nodeA["tx"] // nodeB["tx"]
            >>> nodeA["tx"] = 0
            >>> nodeB["tx"] == 5
            True

        """

        self.disconnect(other)

    def __iter__(self):
        """Iterate over value as a tuple

        Example:
            >>> node = createNode("transform")
            >>> node["translate"] = (0, 1, 2)
            >>> for index, axis in enumerate(node["translate"]):
            ...   assert axis == float(index)
            ...   assert isinstance(axis, Plug)
            ...
            >>> a = createNode("transform")
            >>> a["myArray"] = Message(array=True)
            >>> b = createNode("transform")
            >>> c = createNode("transform")
            >>> a["myArray"][0] << b["message"]
            >>> a["myArray"][1] << c["message"]
            >>> a["myArray"][0] in list(a["myArray"])
            True
            >>> a["myArray"][1] in list(a["myArray"])
            True
            >>> for single in node["visibility"]:
            ...   print(single)
            ...
            True
            >>> node = createNode("wtAddMatrix")
            >>> node["wtMatrix"][0]["weightIn"] = 1.0

        """

        if self._mplug.isArray:
            # getExisting... returns indices currently in use, which is
            # important if the given array is *sparse*. That is, if
            # indexes 5, 7 and 8 are used. If we simply call
            # `evaluateNumElements` then it'll return a single number
            # we could use to `range()` from, but that would only work
            # if the indices were contiguous.
            for index in self._mplug.getExistingArrayAttributeIndices():
                yield self[index]

        elif self._mplug.isCompound:
            for index in range(self._mplug.numChildren()):
                yield self[index]

        else:
            values = self.read()

            # Facilitate single-value attributes
            values = values if isinstance(values, (tuple, list)) else [values]

            for value in values:
                yield value

    def __getitem__(self, index):
        """Read from child of array or compound plug

        Arguments:
            index (int): Logical index of plug (NOT physical, make note)

        Example:
            >>> _ = cmds.file(new=True, force=True)
            >>> node = createNode("transform", name="mynode")
            >>> node["translate"][0].read()
            0.0
            >>> node["visibility"][0]
            Traceback (most recent call last):
            ...
            TypeError: |mynode.visibility does not support indexing
            >>> node["translate"][2] = 5.1
            >>> node["translate"][2].read()
            5.1

        """

        cls = self.__class__

        if isinstance(index, int):
            # Support backwards-indexing
            if index < 0:
                index = self.count() - abs(index)

            if self._mplug.isArray:
                item = self._mplug.elementByLogicalIndex(index)
                return cls(self._node, item, self._unit)

            elif self._mplug.isCompound:
                item = self._mplug.child(index)
                return cls(self._node, item, self._unit)

            else:
                raise TypeError(
                    "%s does not support indexing" % self.path()
                )

        elif isinstance(index, string_types):
            # Compound attributes have no equivalent
            # to "MDependencyNode.findPlug()" and must
            # be searched by hand.
            if self._mplug.isCompound:
                for child in range(self._mplug.numChildren()):
                    child = self._mplug.child(child)
                    _, name = child.name().rsplit(".", 1)

                    if index == name:
                        return cls(self._node, child)

            else:
                raise TypeError("'%s' is not a compound attribute"
                                % self.path())

            raise ExistError("'%s' was not found" % index)

    def __setitem__(self, index, value):
        """Write to child of array or compound plug

        Example:
            >>> node = createNode("transform")
            >>> node["translate"][0] = 5
            >>> node["tx"]
            5.0

        """

        self[index].write(value)

    def __init__(self, node, mplug, unit=None, key=None, modifier=None):
        """A Maya plug

        Arguments:
            node (Node): Parent Node of plug
            mplug (maya.api.OpenMaya.MPlug): Internal Maya plug
            unit (int, optional): Unit with which to read plug

        """

        assert isinstance(node, Node), "%s is not a Node" % node

        self._node = node
        self._mplug = mplug
        self._unit = unit
        self._cached = None
        self._key = key
        self._modifier = modifier

    def plug(self):
        return self._mplug

    @property
    def isArray(self):
        return self._mplug.isArray

    @property
    def isCompound(self):
        return self._mplug.isCompound

    def append(self, value):
        """Add `value` to end of self, which is an array

        Arguments:
            value (object): If value, create a new entry and append it.
                If cmdx.Plug, create a new entry and connect it.

        Example:
            >>> _ = cmds.file(new=True, force=True)
            >>> node = createNode("transform", name="appendTest")
            >>> node["myArray"] = Double(array=True)
            >>> node["myArray"].append(1.0)
            >>> node["notArray"] = Double()
            >>> node["notArray"].append(2.0)
            Traceback (most recent call last):
            ...
            TypeError: "|appendTest.notArray" was not an array attribute

        """

        if not self._mplug.isArray:
            raise TypeError("\"%s\" was not an array attribute" % self.path())

        index = self.count()

        if isinstance(value, Plug):
            self[index] << value
        else:
            self[index].write(value)

    def extend(self, values):
        """Append multiple values to the end of an array

        Arguments:
            values (tuple): If values, create a new entry and append it.
                If cmdx.Plug's, create a new entry and connect it.

        Example:
            >>> node = createNode("transform")
            >>> node["myArray"] = Double(array=True)
            >>> node["myArray"].extend([1.0, 2.0, 3.0])
            >>> node["myArray"][0]
            1.0
            >>> node["myArray"][-1]
            3.0

        """

        for value in values:
            self.append(value)

    def count(self):
        return self._mplug.evaluateNumElements()

    def asDouble(self):
        """Return plug as double (Python float)

        Example:
            >>> node = createNode("transform")
            >>> node["translateX"] = 5.0
            >>> node["translateX"].asDouble()
            5.0

        """

        return self._mplug.asDouble()

    def asMatrix(self, time=None):
        """Return plug as MMatrix

        Example:
            >>> node1 = createNode("transform")
            >>> node2 = createNode("transform", parent=node1)
            >>> node1["translate"] = (0, 5, 0)
            >>> node2["translate"] = (0, 5, 0)
            >>> plug1 = node1["matrix"]
            >>> plug2 = node2["worldMatrix"][0]
            >>> mat1 = plug1.asMatrix()
            >>> mat2 = plug2.asMatrix()
            >>> mat = mat1 * mat2
            >>> tm = TransformationMatrix(mat)
            >>> list(tm.translation())
            [0.0, 15.0, 0.0]

        """

        context = om.MDGContext.kNormal

        if time is not None:
            context = om.MDGContext(om.MTime(time, om.MTime.uiUnit()))

        return om.MFnMatrixData(self._mplug.asMObject(context)).matrix()

    def asTransformationMatrix(self, time=None):
        """Return plug as TransformationMatrix

        Example:
            >>> node = createNode("transform")
            >>> node["translateY"] = 12
            >>> node["rotate"] = 1
            >>> tm = node["matrix"].asTm()
            >>> map(round, tm.rotation())
            [1.0, 1.0, 1.0]
            >>> list(tm.translation())
            [0.0, 12.0, 0.0]

        """

        return TransformationMatrix(self.asMatrix(time))

    # Alias
    asTm = asTransformationMatrix

    def asEulerRotation(self, order=kXYZ, time=None):
        value = self.read(time=time)
        return om.MEulerRotation(value, order)

    def asQuaternion(self, time=None):
        value = self.read(time=time)
        value = Euler(value).asQuaternion()

    def asVector(self):
        assert self.isArray or self.isCompound, "'%s' not an array" % self
        return Vector(self.read())

    @property
    def connected(self):
        """Return whether or not this attribute is connected (to anything)"""
        return self.connection() is not None

    @property
    def locked(self):
        return self._mplug.isLocked

    @locked.setter
    def locked(self, value):
        """Lock attribute"""
        elements = (
            self
            if self.isArray or self.isCompound
            else [self]
        )

        # Use setAttr in place of MPlug.isKeyable = False, as that
        # doesn't persist the scene on save if the attribute is dynamic.
        for el in elements:
            cmds.setAttr(el.path(), lock=value)

    def lock(self):
        self.locked = True

    def unlock(self):
        self.locked = False

    @property
    def channelBox(self):
        """Is the attribute visible in the Channel Box?"""
        if self.isArray or self.isCompound:
            return all(
                plug._mplug.isChannelBox
                for plug in self
            )
        else:
            return self._mplug.isChannelBox

    @channelBox.setter
    def channelBox(self, value):
        elements = (
            self
            if self.isArray or self.isCompound
            else [self]
        )

        # Use setAttr in place of MPlug.isChannelBox = False, as that
        # doesn't persist the scene on save if the attribute is dynamic.
        for el in elements:
            cmds.setAttr(el.path(), keyable=value, channelBox=value)

    @property
    def keyable(self):
        """Is the attribute keyable?"""
        if self.isArray or self.isCompound:
            return all(
                plug._mplug.isKeyable
                for plug in self
            )
        else:
            return self._mplug.isKeyable

    @keyable.setter
    def keyable(self, value):
        elements = (
            self
            if self.isArray or self.isCompound
            else [self]
        )

        # Use setAttr in place of MPlug.isKeyable = False, as that
        # doesn't persist the scene on save if the attribute is dynamic.
        for el in elements:
            cmds.setAttr(el.path(), keyable=value)

    @property
    def hidden(self):
        return om.MFnAttribute(self._mplug.attribute()).hidden

    @hidden.setter
    def hidden(self, value):
        pass

    def hide(self):
        """Hide attribute from channel box

        Note: An attribute cannot be hidden from the channel box
        and keyable at the same time. Therefore, this method
        also makes the attribute non-keyable.

        Supports array and compound attributes too.

        """

        self.keyable = False
        self.channelBox = False

    def lockAndHide(self):
        self.lock()
        self.hide()

    def show(self):
        """Show attribute in channel box

        Note: An attribute can be both visible in the channel box
        and non-keyable, therefore, unlike :func:`hide()`, this
        method does not alter the keyable state of the attribute.

        """

        self.channelBox = True

    def type(self):
        """Retrieve API type of plug as string

        Example:
            >>> node = createNode("transform")
            >>> node["translate"].type()
            'kAttribute3Double'
            >>> node["translateX"].type()
            'kDoubleLinearAttribute'

        """

        return self._mplug.attribute().apiTypeStr

    def path(self):
        return "%s.%s" % (
            self._node.path(), self._mplug.partialName(
                includeNodeName=False,
                useLongNames=True,
                useFullAttributePath=True
            )
        )

    def name(self, long=False):
        return self._mplug.partialName(
            includeNodeName=False,
            useLongNames=long,
            useFullAttributePath=True
        )

    def read(self, unit=None, time=None):
        unit = unit if unit is not None else self._unit
        context = None

        if time is not None:
            context = om.MDGContext(om.MTime(time, om.MTime.uiUnit()))

        try:
            value = _plug_to_python(
                self._mplug,
                unit=unit,
                context=context
            )

            # Store cached value
            self._node._state["values"][self._key, unit] = value

            return value

        except RuntimeError:
            raise

        except TypeError:
            # Expected errors
            log.error("'%s': failed to read attribute" % self.path())
            raise

    def write(self, value):
        if not getattr(self._modifier, "isDone", True):
            return self._modifier.setAttr(self, value)

        try:
            _python_to_plug(value, self)
            self._cached = value

        except RuntimeError:
            raise

        except TypeError:
            log.error("'%s': failed to write attribute" % self.path())
            raise

    def connect(self, other, force=True):
        if not getattr(self._modifier, "isDone", True):
            return self._modifier.connect(self, other, force)

        mod = om.MDGModifier()

        if force:
            # Disconnect any plug connected to `other`
            for plug in other._mplug.connectedTo(True, False):
                mod.disconnect(plug, other._mplug)

        mod.connect(self._mplug, other._mplug)
        mod.doIt()

    def disconnect(self, other=None, source=True, destination=True):
        """Disconnect self from `other`

        Arguments:
            other (Plug, optional): If none is provided, disconnect everything

        Example:
            >>> node1 = createNode("transform")
            >>> node2 = createNode("transform")
            >>> node2["tx"].connection() is None
            True
            >>> node2["ty"].connection() is None
            True
            >>>
            >>> node2["tx"] << node1["tx"]
            >>> node2["ty"] << node1["ty"]
            >>> node2["ty"].connection() is None
            False
            >>> node2["tx"].connection() is None
            False
            >>>
            >>> node2["tx"].disconnect(node1["tx"])
            >>> node2["ty"].disconnect()
            >>> node2["tx"].connection() is None
            True
            >>> node2["ty"].connection() is None
            True

        """

        other = getattr(other, "_mplug", None)

        if not getattr(self._modifier, "isDone", True):
            mod = self._modifier
            mod.disconnect(self._mplug, other, source, destination)
            # Don't do it, leave that to the parent context

        else:
            mod = DGModifier()
            mod.disconnect(self._mplug, other, source, destination)
            mod.doIt()

    def connections(self,
                    type=None,
                    source=True,
                    destination=True,
                    plugs=False,
                    unit=None):
        """Yield plugs connected to self

        Arguments:
            type (int, optional): Only return nodes of this type
            source (bool, optional): Return source plugs,
                default is True
            destination (bool, optional): Return destination plugs,
                default is True
            plugs (bool, optional): Return connected plugs instead of nodes
            unit (int, optional): Return plug in this unit, e.g. Meters

        Example:
            >>> _ = cmds.file(new=True, force=True)
            >>> a = createNode("transform", name="A")
            >>> b = createNode("multDoubleLinear", name="B")
            >>> a["ihi"] << b["ihi"]
            >>> a["ihi"].connection() == b
            True
            >>> b["ihi"].connection() == a
            True
            >>> a["ihi"]
            2

        """

        op = operator.eq
        other = "typeId"

        if isinstance(type, string_types):
            other = "typeName"

        if isinstance(type, (tuple, list)):
            op = operator.contains

        for plug in self._mplug.connectedTo(source, destination):
            mobject = plug.node()
            node = Node(mobject)

            if not type or op(type, getattr(node._fn, other)):
                yield Plug(node, plug, unit) if plugs else node

    def connection(self,
                   type=None,
                   source=True,
                   destination=True,
                   plug=False,
                   unit=None):
        """Return first connection from :func:`connections()`"""
        return next(self.connections(type=type,
                                     source=source,
                                     destination=destination,
                                     plugs=plug,
                                     unit=unit), None)

    def source(self, unit=None):
        cls = self.__class__
        plug = self._mplug.source()
        node = Node(plug.node())

        if not plug.isNull:
            return cls(node, plug, unit)

    def node(self):
        return self._node

    if ENABLE_PEP8:
        as_double = asDouble
        as_matrix = asMatrix
        as_transformation_matrix = asTransformationMatrix
        as_euler_rotation = asEulerRotation
        as_quaternion = asQuaternion
        as_vector = asVector
        channel_box = channelBox
        lock_and_hide = lockAndHide


class TransformationMatrix(om.MTransformationMatrix):
    """A more readable version of Maya's MTransformationMatrix

    Added:
        - Takes tuples/lists in place of MVector and other native types
        - Support for multiplication
        - Support for getting individual axes
        - Support for direct access to the quaternion

    Arguments:
        matrix (Matrix, TransformationMatrix, optional): Original constructor
        translate (tuple, Vector, optional): Initial translate value
        rotate (tuple, Vector, optional): Initial rotate value
        scale (tuple, Vector, optional): Initial scale value

    """

    def __init__(self, matrix=None, translate=None, rotate=None, scale=None):

        # It doesn't like being handed `None`
        args = [matrix] if matrix is not None else []

        super(TransformationMatrix, self).__init__(*args)

        if translate is not None:
            self.setTranslation(translate)

        if rotate is not None:
            self.setRotation(rotate)

        if scale is not None:
            self.setScale(scale)

    def __mul__(self, other):
        if isinstance(other, (tuple, list)):
            other = Vector(*other)

        if isinstance(other, om.MVector):
            p = self.translation()
            q = self.quaternion()
            return p + q * other

        elif isinstance(other, om.MMatrix):
            return type(self)(self.asMatrix() * other)

        elif isinstance(other, om.MTransformationMatrix):
            return type(self)(self.asMatrix() * other.asMatrix())

        else:
            raise TypeError(
                "unsupported operand type(s) for *: '%s' and '%s'"
                % (type(self).__name__, type(other).__name__)
            )

    @property
    def xAxis(self):
        return self.quaternion() * Vector(1, 0, 0)

    @property
    def yAxis(self):
        return self.quaternion() * Vector(0, 1, 0)

    @property
    def zAxis(self):
        return self.quaternion() * Vector(0, 0, 1)

    def translateBy(self, vec, space=None):
        space = space or sTransform
        if isinstance(vec, (tuple, list)):
            vec = Vector(vec)
        return super(TransformationMatrix, self).translateBy(vec, space)

    def rotateBy(self, vec, space=None):
        """Handle arguments conveniently

        - Allow for optional `space` argument
        - Automatically convert tuple to Vector

        """

        space = space or sTransform
        if isinstance(vec, (tuple, list)):
            vec = Vector(vec)

        if isinstance(vec, om.MVector):
            vec = EulerRotation(vec)

        return super(TransformationMatrix, self).rotateBy(vec, space)

    def quaternion(self):
        """Return transformation matrix as a Quaternion"""
        return Quaternion(self.rotation(asQuaternion=True))

    def rotatePivot(self, space=None):
        """This method does not typically support optional arguments"""
        space = space or sTransform
        return super(TransformationMatrix, self).rotatePivot(space)

    def translation(self, space=None):
        """This method does not typically support optional arguments"""
        space = space or sTransform
        return super(TransformationMatrix, self).translation(space)

    def setTranslation(self, trans, space=None):
        if isinstance(trans, Plug):
            trans = trans.as_vector()

        if isinstance(trans, (tuple, list)):
            trans = Vector(*trans)

        space = space or sTransform
        return super(TransformationMatrix, self).setTranslation(trans, space)

    def scale(self, space=None):
        """This method does not typically support optional arguments"""
        space = space or sTransform
        return Vector(super(TransformationMatrix, self).scale(space))

    def setScale(self, seq, space=None):
        """This method does not typically support optional arguments"""
        if isinstance(seq, Plug):
            seq = seq.as_vector()

        if isinstance(seq, (tuple, list)):
            seq = Vector(*seq)

        space = space or sTransform
        return super(TransformationMatrix, self).setScale(seq, space)

    def rotation(self, asQuaternion=False):
        return super(TransformationMatrix, self).rotation(asQuaternion)

    def setRotation(self, rot):
        """Interpret three values as an euler rotation"""
        if isinstance(rot, Plug):
            rot = rot.as_vector()

        if isinstance(rot, (tuple, list)):
            try:
                rot = Vector(rot)
            except ValueError:
                traceback.print_exc()
                raise ValueError(
                    "I tried automatically converting your "
                    "tuple to a Vector, but couldn't.."
                )

        if isinstance(rot, Vector):
            rot = EulerRotation(rot)

        return super(TransformationMatrix, self).setRotation(rot)

    def asMatrix(self):
        return super(TransformationMatrix, self).asMatrix()

    def asMatrixInverse(self):
        return super(TransformationMatrix, self).asMatrixInverse()

    if ENABLE_PEP8:
        x_axis = xAxis
        y_axis = yAxis
        z_axis = zAxis
        translate_by = translateBy
        rotate_by = rotateBy
        set_translation = setTranslation
        set_rotation = setRotation
        set_scale = setScale
        as_matrix = asMatrix
        as_matrix_inverse = asMatrixInverse


class MatrixType(om.MMatrix):
    pass


# Alias
Transformation = TransformationMatrix
Tm = TransformationMatrix
Mat = MatrixType


class Vector(om.MVector):
    """Maya's MVector

    Example:
        >>> vec = Vector(1, 0, 0)
        >>> vec * Vector(0, 1, 0)  # Dot product
        0.0
        >>> vec ^ Vector(0, 1, 0)  # Cross product
        maya.api.OpenMaya.MVector(0, 0, 1)

    """

    def __add__(self, value):
        if isinstance(value, (int, float)):
            return type(self)(
                self.x + value,
                self.y + value,
                self.z + value,
            )

        return super(Vector, self).__add__(value)

    def __iadd__(self, value):
        if isinstance(value, (int, float)):
            return type(self)(
                self.x + value,
                self.y + value,
                self.z + value,
            )

        return super(Vector, self).__iadd__(value)


# Alias, it can't take anything other than values
# and yet it isn't explicit in its name.
Vector3 = Vector


class Point(om.MPoint):
    """Maya's MPoint"""


class BoundingBox(om.MBoundingBox):
    """Maya's MBoundingBox"""


class Quaternion(om.MQuaternion):
    """Maya's MQuaternion

    Example:
        >>> q = Quaternion(0, 0, 0, 1)
        >>> v = Vector(1, 2, 3)
        >>> isinstance(q * v, Vector)
        True

    """

    def __mul__(self, other):
        if isinstance(other, (tuple, list)):
            other = Vector(*other)

        if isinstance(other, om.MVector):
            return Vector(other.rotateBy(self))

        else:
            return super(Quaternion, self).__mul__(other)

    def lengthSquared(self):
        return (
            self.x * self.x +
            self.y * self.y +
            self.z * self.z +
            self.w * self.w
        )

    def length(self):
        return math.sqrt(self.lengthSquared())

    def isNormalised(self, tol=0.0001):
        return abs(self.length() - 1.0) < tol


# Alias
Quat = Quaternion


def twistSwingToQuaternion(ts):
    """Convert twist/swing1/swing2 rotation in a Vector into a quaternion

    Arguments:
        ts (Vector): Twist, swing1 and swing2

    """

    t = tan(ts.x * 0.25)
    s1 = tan(ts.y * 0.25)
    s2 = tan(ts.z * 0.25)

    b = 2.0 / (1.0 + s1 * s1 + s2 * s2)
    c = 2.0 / (1.0 + t * t)

    quat = Quaternion()
    quat.w = (b - 1.0) * (c - 1.0)
    quat.x = -t * (b - 1.0) * c
    quat.y = -b * (c * t * s1 + (c - 1.0) * s2)
    quat.z = -b * (c * t * s2 - (c - 1.0) * s1)

    assert quat.isNormalised()
    return quat


class EulerRotation(om.MEulerRotation):
    def asQuaternion(self):
        return super(EulerRotation, self).asQuaternion()

    if ENABLE_PEP8:
        as_quaternion = asQuaternion


# Alias
Euler = EulerRotation


def NurbsCurveData(points, degree=1, form=om1.MFnNurbsCurve.kOpen):
    """Tuple of points to MObject suitable for nurbsCurve-typed data

    Arguments:
        points (tuple): (x, y, z) tuples per point
        degree (int, optional): Defaults to 1 for linear
        form (int, optional): Defaults to MFnNurbsCurve.kOpen,
            also available kClosed

    Example:
        Create a new nurbs curve like this.

        >>> data = NurbsCurveData(
        ...     points=(
        ...         (0, 0, 0),
        ...         (0, 1, 0),
        ...         (0, 2, 0),
        ...     ))
        ...
        >>> parent = createNode("transform")
        >>> shape = createNode("nurbsCurve", parent=parent)
        >>> shape["cached"] = data

    """

    degree = min(3, max(1, degree))

    cvs = om1.MPointArray()
    curveFn = om1.MFnNurbsCurve()
    data = om1.MFnNurbsCurveData()
    mobj = data.create()

    for point in points:
        cvs.append(om1.MPoint(*point))

    curveFn.createWithEditPoints(cvs,
                                 degree,
                                 form,
                                 False,
                                 False,
                                 True,
                                 mobj)

    return mobj


class CachedPlug(Plug):
    """Returned in place of an actual plug"""

    def __init__(self, value):
        self._value = value

    def read(self):
        return self._value


def _plug_to_python(plug, unit=None, context=None):
    """Convert native `plug` to Python type

    Arguments:
        plug (om.MPlug): Native Maya plug
        unit (int, optional): Return value in this unit, e.g. Meters
        context (om.MDGContext, optional): Return value in this context

    """

    assert not plug.isNull, "'%s' was null" % plug

    if context is None:
        context = om.MDGContext.kNormal

    # Multi attributes
    #   _____
    #  |     |
    #  |     ||
    #  |     ||
    #  |_____||
    #   |_____|
    #

    if plug.isArray and plug.isCompound:
        # E.g. locator["worldPosition"]
        return _plug_to_python(
            plug.elementByLogicalIndex(0), unit, context
        )

    elif plug.isArray:
        # E.g. transform["worldMatrix"][0]
        # E.g. locator["worldPosition"][0]
        return tuple(
            _plug_to_python(
                plug.elementByLogicalIndex(index),
                unit,
                context
            )
            for index in range(plug.evaluateNumElements())
        )

    elif plug.isCompound:
        return tuple(
            _plug_to_python(plug.child(index), unit, context)
            for index in range(plug.numChildren())
        )

    # Simple attributes
    #   _____
    #  |     |
    #  |     |
    #  |     |
    #  |_____|
    #
    attr = plug.attribute()
    type = attr.apiType()
    if type == om.MFn.kTypedAttribute:
        innerType = om.MFnTypedAttribute(attr).attrType()

        if innerType == om.MFnData.kAny:
            # E.g. choice["input"][0]
            return None

        elif innerType == om.MFnData.kMatrix:
            # E.g. transform["worldMatrix"][0]
            if plug.isArray:
                plug = plug.elementByLogicalIndex(0)

            return tuple(
                om.MFnMatrixData(plug.asMObject(context)).matrix()
            )

        elif innerType == om.MFnData.kString:
            return plug.asString(context)

        elif innerType == om.MFnData.kNurbsCurve:
            return om.MFnNurbsCurveData(plug.asMObject(context))

        elif innerType == om.MFnData.kComponentList:
            return None

        elif innerType == om.MFnData.kInvalid:
            # E.g. time1.timewarpIn_Hidden
            # Unsure of why some attributes are invalid
            return None

        else:
            log.debug("Unsupported kTypedAttribute: %s" % innerType)
            return None

    elif type == om.MFn.kMatrixAttribute:
        return tuple(om.MFnMatrixData(plug.asMObject(context)).matrix())

    elif type == om.MFnData.kDoubleArray:
        raise TypeError("%s: kDoubleArray is not supported" % plug)

    elif type in (om.MFn.kDoubleLinearAttribute,
                  om.MFn.kFloatLinearAttribute):

        if unit is None:
            return plug.asMDistance(context).asUnits(Centimeters)
        elif unit == Millimeters:
            return plug.asMDistance(context).asMillimeters()
        elif unit == Centimeters:
            return plug.asMDistance(context).asCentimeters()
        elif unit == Meters:
            return plug.asMDistance(context).asMeters()
        elif unit == Kilometers:
            return plug.asMDistance(context).asKilometers()
        elif unit == Inches:
            return plug.asMDistance(context).asInches()
        elif unit == Feet:
            return plug.asMDistance(context).asFeet()
        elif unit == Miles:
            return plug.asMDistance(context).asMiles()
        elif unit == Yards:
            return plug.asMDistance(context).asYards()
        else:
            raise TypeError("Unsupported unit '%d'" % unit)

    elif type in (om.MFn.kDoubleAngleAttribute,
                  om.MFn.kFloatAngleAttribute):
        if unit is None:
            return plug.asMAngle(context).asUnits(Radians)
        elif unit == Degrees:
            return plug.asMAngle(context).asDegrees()
        elif unit == Radians:
            return plug.asMAngle(context).asRadians()
        elif unit == AngularSeconds:
            return plug.asMAngle(context).asAngSeconds()
        elif unit == AngularMinutes:
            return plug.asMAngle(context).asAngMinutes()
        else:
            raise TypeError("Unsupported unit '%d'" % unit)

    # Number
    elif type == om.MFn.kNumericAttribute:
        innerType = om.MFnNumericAttribute(attr).numericType()

        if innerType == om.MFnNumericData.kBoolean:
            return plug.asBool(context)

        elif innerType in (om.MFnNumericData.kShort,
                           om.MFnNumericData.kInt,
                           om.MFnNumericData.kLong,
                           om.MFnNumericData.kByte):
            return plug.asInt(context)

        elif innerType in (om.MFnNumericData.kFloat,
                           om.MFnNumericData.kDouble,
                           om.MFnNumericData.kAddr):
            return plug.asDouble(context)

        else:
            raise TypeError("Unsupported numeric type: %s"
                            % innerType)

    # Enum
    elif type == om.MFn.kEnumAttribute:
        return plug.asShort(context)

    elif type == om.MFn.kMessageAttribute:
        # In order to comply with `if plug:`
        return True

    elif type == om.MFn.kTimeAttribute:
        return plug.asShort(context)

    elif type == om.MFn.kInvalid:
        raise TypeError("%s was invalid" % plug.name())

    else:
        raise TypeError("Unsupported type '%s'" % type)


def _python_to_plug(value, plug):
    """Pass value of `value` to `plug`

    Arguments:
        value (any): Instance of Python or Maya type
        plug (Plug): Target plug to which value is applied

    """

    # Compound values

    if isinstance(value, (tuple, list)):
        for index, value in enumerate(value):

            # Tuple values are assumed flat:
            #   e.g. (0, 0, 0, 0)
            # Nested values are not supported:
            #   e.g. ((0, 0), (0, 0))
            # Those can sometimes appear in e.g. matrices
            if isinstance(value, (tuple, list)):
                raise TypeError(
                    "Unsupported nested Python type: %s"
                    % value.__class__
                )

            _python_to_plug(value, plug[index])

    # Native Maya types

    elif isinstance(value, om1.MObject):
        node = _encode1(plug._node.path())
        shapeFn = om1.MFnDagNode(node)
        plug = shapeFn.findPlug(plug.name())
        plug.setMObject(value)

    elif isinstance(value, om.MEulerRotation):
        for index, value in enumerate(value):
            value = om.MAngle(value, om.MAngle.kRadians)
            _python_to_plug(value, plug[index])

    elif isinstance(value, om.MAngle):
        plug._mplug.setMAngle(value)

    elif isinstance(value, om.MDistance):
        plug._mplug.setMDistance(value)

    elif isinstance(value, om.MTime):
        plug._mplug.setMTime(value)

    elif isinstance(value, om.MQuaternion):
        _python_to_plug(value.asEulerRotation(), plug)

    elif isinstance(value, om.MVector):
        for index, value in enumerate(value):
            _python_to_plug(value, plug[index])

    elif isinstance(value, om.MPoint):
        for index, value in enumerate(value):
            _python_to_plug(value, plug[index])

    elif plug._mplug.isCompound:
        count = plug._mplug.numChildren()
        return _python_to_plug([value] * count, plug)

    # Native Python types

    elif isinstance(value, string_types):
        plug._mplug.setString(value)

    elif isinstance(value, int):
        plug._mplug.setInt(value)

    elif isinstance(value, float):
        plug._mplug.setDouble(value)

    elif isinstance(value, bool):
        plug._mplug.setBool(value)

    else:
        raise TypeError("Unsupported Python type '%s'" % value.__class__)


def _python_to_mod(value, plug, mod):
    """Convert `value` into a suitable equivalent for om.MDGModifier

    Arguments:
        value (object): Value of any type to write into modifier
        plug (Plug): Plug within which to write value
        mod (om.MDGModifier): Modifier to use for writing it

    """

    mplug = plug._mplug

    if isinstance(value, (tuple, list)):
        for index, value in enumerate(value):

            # Tuple values are assumed flat:
            #   e.g. (0, 0, 0, 0)
            # Nested values are not supported:
            #   e.g. ((0, 0), (0, 0))
            # Those can sometimes appear in e.g. matrices
            if isinstance(value, (tuple, list)):
                raise TypeError(
                    "Unsupported nested Python type: %s"
                    % value.__class__
                )

            _python_to_mod(value, plug[index], mod)

    elif isinstance(value, om.MVector):
        for index, value in enumerate(value):
            _python_to_mod(value, plug[index], mod)

    elif isinstance(value, string_types):
        mod.newPlugValueString(mplug, value)

    elif isinstance(value, int):
        mod.newPlugValueInt(mplug, value)

    elif isinstance(value, float):
        mod.newPlugValueFloat(mplug, value)

    elif isinstance(value, bool):
        mod.newPlugValueBool(mplug, value)

    elif isinstance(value, om.MAngle):
        mod.newPlugValueMAngle(mplug, value)

    elif isinstance(value, om.MDistance):
        mod.newPlugValueMDistance(mplug, value)

    elif isinstance(value, om.MTime):
        mod.newPlugValueMTime(mplug, value)

    elif isinstance(value, om.MEulerRotation):
        for index, value in enumerate(value):
            value = om.MAngle(value, om.MAngle.kRadians)
            _python_to_mod(value, plug[index], mod)

    else:
        log.warning(
            "Unsupported plug type for modifier: %s" % type(value)
        )
        return False
    return True


def encode(path):
    """Convert relative or absolute `path` to cmdx Node

    Fastest conversion from absolute path to Node

    Arguments:
        path (str): Absolute or relative path to DAG or DG node

    """

    assert isinstance(path, string_types), "%s was not string" % path

    selectionList = om.MSelectionList()

    try:
        selectionList.add(path)
    except RuntimeError:
        raise ExistError("'%s' does not exist" % path)

    mobj = selectionList.getDependNode(0)
    return Node(mobj)


def fromHash(code, default=None):
    """Get existing node from MObjectHandle.hashCode()"""
    try:
        return Singleton._instances["%x" % code]
    except IndexError:
        return default


def fromHex(hex, default=None, safe=True):
    """Get existing node from Node.hex"""
    node = Singleton._instances.get(hex, default)
    if safe and node and node.exists:
        return node
    else:
        return node


def toHash(mobj):
    """Cache the given `mobj` and return its hashCode

    This enables pre-caching of one or more nodes in situations where
    intend to access it later, at a more performance-critical moment.

    Ignores nodes that have already been cached.

    """

    node = Node(mobj)
    return node.hashCode


def toHex(mobj):
    """Cache the given `mobj` and return its hex value

    See :func:`toHash` for docstring.

    """

    node = Node(mobj)
    return node.hex


def asHash(mobj):
    """Return a given hashCode for `mobj`, without caching it

    This can be helpful in case you wish to synchronise `cmdx`
    with a third-party library or tool and wish to guarantee
    that an identical algorithm is used.

    """

    handle = om.MObjectHandle(mobj)
    return handle.hashCode()


def asHex(mobj):
    """Return a given hex string for `mobj`, without caching it

    See docstring for :func:`asHash` for details

    """

    return "%x" % asHash(mobj)


if ENABLE_PEP8:
    from_hash = fromHash
    from_hex = fromHex
    to_hash = toHash
    to_hex = toHex
    as_hash = asHash
    as_hex = asHex


# Helpful for euler rotations
degrees = math.degrees
radians = math.radians
sin = math.sin
cos = math.cos
tan = math.tan
pi = math.pi


def meters(cm):
    """Centimeters (Maya's default unit) to Meters

    Example:
        >>> meters(100)
        1.0

    """

    return cm * 0.01


def clear():
    """Remove all reused nodes"""
    Singleton._instances.clear()


def _encode1(path):
    """Convert `path` to Maya API 1.0 MObject

    Arguments:
        path (str): Absolute or relative path to DAG or DG node

    Raises:
        ExistError on `path` not existing

    """

    selectionList = om1.MSelectionList()

    try:
        selectionList.add(path)
    except RuntimeError:
        raise ExistError("'%s' does not exist" % path)

    mobject = om1.MObject()
    selectionList.getDependNode(0, mobject)
    return mobject


def _encodedagpath1(path):
    """Convert `path` to Maya API 1.0 MObject

    Arguments:
        path (str): Absolute or relative path to DAG or DG node

    Raises:
        ExistError on `path` not existing

    """

    selectionList = om1.MSelectionList()

    try:
        selectionList.add(path)
    except RuntimeError:
        raise ExistError("'%s' does not exist" % path)

    dagpath = om1.MDagPath()
    selectionList.getDagPath(0, dagpath)
    return dagpath


def decode(node):
    """Convert cmdx Node to shortest unique path

    This is the same as `node.shortestPath()`
    To get an absolute path, use `node.path()`

    """

    try:
        return node.shortestPath()
    except AttributeError:
        return node.name(namespace=True)


def record_history(func):
    @wraps(func)
    def decorator(self, *args, **kwargs):
        _kwargs = kwargs.copy()
        _args = list(args)

        # Don't store actual objects,
        # to facilitate garbage collection.
        for index, arg in enumerate(args):
            if isinstance(arg, (Node, Plug)):
                _args[index] = arg.path()
            else:
                _args[index] = repr(arg)

        for key, value in kwargs.items():
            if isinstance(value, (Node, Plug)):
                _kwargs[key] = value.path()
            else:
                _kwargs[key] = repr(value)

        self._history.append((func.__name__, _args, _kwargs))

        return func(self, *args, **kwargs)

    return decorator


class _BaseModifier(object):
    """Interactively edit an existing scenegraph with support for undo/redo

    Arguments:
        undoable (bool, optional): Put undoIt on the undo queue
        interesting (bool, optional): New nodes should appear
            in the channelbox
        debug (bool, optional): Include additional debug data,
            at the expense of performance
        atomic (bool, optional): Automatically rollback changes on failure
        template (str, optional): Automatically name new nodes using
            this template

    """

    Type = om.MDGModifier

    def __enter__(self):
        self.isContext = True
        return self

    def __exit__(self, exc_type, exc_value, tb):

        # Support calling `doIt` during a context,
        # without polluting the undo queue.
        if self.isContext and self._opts["undoable"]:
            commit(self._modifier.undoIt, self._modifier.doIt)

        self.doIt()

    def __init__(self,
                 undoable=True,
                 interesting=True,
                 debug=True,
                 atomic=True,
                 template=None):
        super(_BaseModifier, self).__init__()
        self.isDone = False
        self.isContext = False

        self._modifier = self.Type()
        self._history = list()
        self._index = 1
        self._opts = {
            "undoable": undoable,
            "interesting": interesting,
            "debug": debug,
            "atomic": atomic,
            "template": template,
        }

    def doIt(self):
        if (not self.isContext) and self._opts["undoable"]:
            commit(self._modifier.undoIt, self._modifier.doIt)

        try:
            self._modifier.doIt()

        except RuntimeError:

            # Rollback changes
            if self._opts["atomic"]:
                self.undoIt()

            raise ModifierError(self._history)

        self.isDone = True

    def undoIt(self):
        self._modifier.undoIt()

    @record_history
    def createNode(self, type, name=None):
        try:
            mobj = self._modifier.createNode(type)
        except TypeError:
            raise TypeError("'%s' is not a valid node type" % type)

        template = self._opts["template"]
        if name or template:
            name = (template or "{name}").format(
                name=name or "",
                type=type,
                index=self._index,
            )
            self._modifier.renameNode(mobj, name)

        node = Node(mobj, exists=False, modifier=self)

        if not self._opts["interesting"]:
            plug = node["isHistoricallyInteresting"]
            _python_to_mod(False, plug, self._modifier)

        self._index += 1
        return node

    @record_history
    def deleteNode(self, node):
        return self._modifier.deleteNode(node._mobject)

    delete = deleteNode

    @record_history
    def renameNode(self, node, name):
        return self._modifier.renameNode(node._mobject, name)

    rename = renameNode

    @record_history
    def setAttr(self, plug, value):
        if isinstance(value, Plug):
            value = value.read()

        if isinstance(plug, om.MPlug):
            value = Plug(plug.node(), plug).read()

        _python_to_mod(value, plug, self._modifier)

    @record_history
    def connect(self, src, dst, force=True):
        if isinstance(src, Plug):
            src = src._mplug

        if isinstance(dst, Plug):
            dst = dst._mplug

        if force:
            # Disconnect any plug connected to `other`
            for plug in dst.connectedTo(True, False):
                self.disconnect(plug, dst)

        self._modifier.connect(src, dst)

    @record_history
    def disconnect(self, a, b=None, source=True, destination=True):
        """Disconnect `a` from `b`

        Arguments:
            a (Plug): Starting point of a connection
            b (Plug, optional): End point of a connection, defaults to all
            source (bool, optional): Disconnect b, if it is a source
            source (bool, optional): Disconnect b, if it is a destination

        Normally, Maya only performs a disconnect if the
        connection is incoming. Bidirectional

        disconnect(A, B) => OK
         __________       _________
        |          |     |         |
        |  nodeA   o---->o  nodeB  |
        |__________|     |_________|

        disconnect(B, A) => NO
         __________       _________
        |          |     |         |
        |  nodeA   o---->o  nodeB  |
        |__________|     |_________|

        """

        if isinstance(a, Plug):
            a = a._mplug

        if isinstance(b, Plug):
            b = b._mplug

        if b is None:
            # Disconnect any plug connected to `other`
            if source:
                for plug in a.connectedTo(True, False):
                    self._modifier.disconnect(plug, a)

            if destination:
                for plug in a.connectedTo(False, True):
                    self._modifier.disconnect(a, plug)

        else:
            if source:
                self._modifier.disconnect(a, b)

            if destination:
                self._modifier.disconnect(b, a)

    if ENABLE_PEP8:
        do_it = doIt
        undo_it = undoIt
        create_node = createNode
        delete_node = deleteNode
        rename_node = renameNode
        set_attr = setAttr


class DGModifier(_BaseModifier):
    """Modifier for DG nodes"""

    Type = om.MDGModifier


class DagModifier(_BaseModifier):
    """Modifier for DAG nodes

    Example:
        >>> with DagModifier() as mod:
        ...     node1 = mod.createNode("transform")
        ...     node2 = mod.createNode("transform", parent=node1)
        ...     mod.setAttr(node1["translate"], (1, 2, 3))
        ...     mod.connect(node1 + ".translate", node2 + ".translate")
        ...
        >>> getAttr(node1 + ".translateX")
        1.0
        >>> node2["translate"][0]
        1.0
        >>> node2["translate"][1]
        2.0
        >>> with DagModifier() as mod:
        ...     node1 = mod.createNode("transform")
        ...     node2 = mod.createNode("transform", parent=node1)
        ...     node1["translate"] = (5, 6, 7)
        ...     node1["translate"] >> node2["translate"]
        ...
        >>> node2["translate"][0]
        5.0
        >>> node2["translate"][1]
        6.0

    Example, without context manager:
        >>> mod = DagModifier()
        >>> parent = mod.createNode("transform")
        >>> shape = mod.createNode("transform", parent=parent)
        >>> mod.connect(parent["tz"], shape["tz"])
        >>> mod.setAttr(parent["sx"], 2.0)
        >>> parent["tx"] >> shape["ty"]
        >>> parent["tx"] = 5.1
        >>> round(shape["ty"], 1)  # Not yet created nor connected
        0.0
        >>> mod.doIt()
        >>> round(shape["ty"], 1)
        5.1
        >>> round(parent["sx"])
        2.0

    Duplicate names are resolved, even though nodes haven't yet been created:
        >>> _ = cmds.file(new=True, force=True)
        >>> with DagModifier() as mod:
        ...     node = mod.createNode("transform", name="NotUnique")
        ...     node1 = mod.createNode("transform", name="NotUnique")
        ...     node2 = mod.createNode("transform", name="NotUnique")
        ...
        >>> node.name() == "NotUnique"
        True
        >>> node1.name() == "NotUnique1"
        True
        >>> node2.name() == "NotUnique2"
        True

    Deletion works too
        >>> _ = cmds.file(new=True, force=True)
        >>> mod = DagModifier()
        >>> parent = mod.createNode("transform", name="myParent")
        >>> child = mod.createNode("transform", name="myChild", parent=parent)
        >>> mod.doIt()
        >>> "myParent" in cmds.ls()
        True
        >>> "myChild" in cmds.ls()
        True
        >>> parent.child().name()
        u'myChild'
        >>> mod = DagModifier()
        >>> _ = mod.delete(child)
        >>> mod.doIt()
        >>> parent.child() is None
        True
        >>> "myChild" in cmds.ls()
        False

    """

    Type = om.MDagModifier

    @record_history
    def createNode(self, type, name=None, parent=None):
        parent = parent._mobject if parent else om.MObject.kNullObj

        try:
            mobj = self._modifier.createNode(type, parent)
        except TypeError:
            raise TypeError("'%s' is not a valid node type" % type)

        template = self._opts["template"]
        if name or template:
            name = (template or "{name}").format(
                name=name or "",
                type=type,
                index=self._index,
            )
            self._modifier.renameNode(mobj, name)

        return DagNode(mobj, exists=False, modifier=self)

    @record_history
    def parent(self, node, parent=None):
        parent = parent._mobject if parent is not None else None
        self._modifier.reparentNode(node._mobject, parent)

    if ENABLE_PEP8:
        create_node = createNode


def ls(*args, **kwargs):
    return map(encode, cmds.ls(*args, **kwargs))


def selection(*args, **kwargs):
    return map(encode, cmds.ls(*args, selection=True, **kwargs))


def createNode(type, name=None, parent=None):
    """Create a new node

    This function forms the basic building block
    with which to create new nodes in Maya.

    .. note:: Missing arguments `shared` and `skipSelect`
    .. tip:: For additional performance, `type` may be given as an MTypeId

    Arguments:
        type (str): Type name of new node, e.g. "transform"
        name (str, optional): Sets the name of the newly-created node
        parent (Node, optional): Specifies the parent in the DAG under which
            the new node belongs

    Example:
        >>> node = createNode("transform")  # Type as string
        >>> node = createNode(tTransform)  # Type as ID

    """

    try:
        with DagModifier() as mod:
            node = mod.createNode(type, name=name, parent=parent)

    except TypeError:
        with DGModifier() as mod:
            node = mod.createNode(type, name=name)

    return node


def getAttr(attr, type=None):
    """Read `attr`

    Arguments:
        attr (Plug): Attribute as a cmdx.Plug
        type (str, optional): Unused

    Example:
        >>> node = createNode("transform")
        >>> getAttr(node + ".translateX")
        0.0

    """

    return attr.read()


def setAttr(attr, value, type=None):
    """Write `value` to `attr`

    Arguments:
        attr (Plug): Existing attribute to edit
        value (any): Value to write
        type (int, optional): Unused

    Example:
        >>> node = createNode("transform")
        >>> setAttr(node + ".translateX", 5.0)

    """

    attr.write(value)


def addAttr(node,
            longName,
            attributeType,
            shortName=None,
            enumName=None,
            defaultValue=None):
    """Add new attribute to `node`

    Arguments:
        node (Node): Add attribute to this node
        longName (str): Name of resulting attribute
        attributeType (str): Type of attribute, e.g. `string`
        shortName (str, optional): Alternate name of attribute
        enumName (str, optional): Options for an enum attribute
        defaultValue (any, optional): Default value of attribute

    Example:
        >>> node = createNode("transform")
        >>> addAttr(node, "myString", attributeType="string")
        >>> addAttr(node, "myDouble", attributeType=Double)

    """

    at = attributeType
    if isinstance(at, type) and issubclass(at, _AbstractAttribute):
        Attribute = attributeType

    else:
        # Support legacy maya.cmds interface
        Attribute = {
            "double": Double,
            "double3": Double3,
            "string": String,
            "long": Long,
            "bool": Boolean,
            "enume": Enum,
        }[attributeType]

    kwargs = {
        "default": defaultValue
    }

    if enumName:
        kwargs["fields"] = enumName.split(":")

    attribute = Attribute(longName, **kwargs)
    node.addAttr(attribute)


def listRelatives(node,
                  type=None,
                  children=False,
                  allDescendents=False,
                  parent=False,
                  shapes=False):
    """List relatives of `node`

    Arguments:
        node (DagNode): Node to enquire about
        type (int, optional): Only return nodes of this type
        children (bool, optional): Return children of `node`
        parent (bool, optional): Return parent of `node`
        shapes (bool, optional): Return only children that are shapes
        allDescendents (bool, optional): Return descendents of `node`
        fullPath (bool, optional): Unused; nodes are always exact
        path (bool, optional): Unused; nodes are always exact

    Example:
        >>> parent = createNode("transform")
        >>> child = createNode("transform", parent=parent)
        >>> listRelatives(child, parent=True) == [parent]
        True

    """

    if not isinstance(node, DagNode):
        return None

    elif allDescendents:
        return list(node.descendents(type=type))

    elif shapes:
        return list(node.shapes(type=type))

    elif parent:
        return [node.parent(type=type)]

    elif children:
        return list(node.children(type=type))


def listConnections(attr):
    """List connections of `attr`

    Arguments:
        attr (Plug or Node):

    Example:
        >>> node1 = createNode("transform")
        >>> node2 = createNode("mesh", parent=node1)
        >>> node1["v"] >> node2["v"]
        >>> listConnections(node1) == [node2]
        True
        >>> listConnections(node1 + ".v") == [node2]
        True
        >>> listConnections(node1["v"]) == [node2]
        True
        >>> listConnections(node2) == [node1]
        True

    """

    return list(node for node in attr.connections())


def connectAttr(src, dst):
    """Connect `src` to `dst`

    Arguments:
        src (Plug): Source plug
        dst (Plug): Destination plug

    Example:
        >>> src = createNode("transform")
        >>> dst = createNode("transform")
        >>> connectAttr(src + ".rotateX", dst + ".scaleY")

    """

    src.connect(dst)


def delete(*nodes):
    with DGModifier() as mod:
        for node in nodes:
            mod.delete(node)


def rename(node, name):
    with DGModifier() as mod:
        mod.rename(node, name)


def parent(children, parent, relative=True, absolute=False):
    assert isinstance(parent, DagNode), "parent must be DagNode"

    if not isinstance(children, (tuple, list)):
        children = [children]

    for child in children:
        assert isinstance(child, DagNode), "child must be DagNode"
        parent.addChild(child)


def objExists(obj):
    if isinstance(obj, (Node, Plug)):
        obj = obj.path()

    try:
        om.MSelectionList().add(obj)
    except RuntimeError:
        return False
    else:
        return True


# PEP08
sl = selection
create_node = createNode
get_attr = getAttr
set_attr = setAttr
add_attr = addAttr
list_relatives = listRelatives
list_connections = listConnections
connect_attr = connectAttr
obj_exists = objExists

# Speciality functions

kOpen = om1.MFnNurbsCurve.kOpen
kClosed = om1.MFnNurbsCurve.kClosed
kPeriodic = om1.MFnNurbsCurve.kPeriodic


def editCurve(parent, points, degree=1, form=kOpen):
    assert isinstance(parent, DagNode), (
        "parent must be of type cmdx.DagNode"
    )

    degree = min(3, max(1, degree))

    cvs = om1.MPointArray()
    curveFn = om1.MFnNurbsCurve()

    for point in points:
        cvs.append(om1.MPoint(*point))

    mobj = curveFn.createWithEditPoints(cvs,
                                        degree,
                                        form,
                                        False,
                                        False,
                                        True,
                                        _encode1(parent.path()))

    mod = om1.MDagModifier()
    mod.renameNode(mobj, parent.name(namespace=True) + "Shape")
    mod.doIt()

    def undo():
        mod.deleteNode(mobj)
        mod.doIt()

    def redo():
        mod.undoIt()

    commit(undo, redo)

    shapeFn = om1.MFnDagNode(mobj)
    return encode(shapeFn.fullPathName())


def curve(parent, points, degree=1, form=kOpen):
    """Create a NURBS curve from a series of points

    Arguments:
        parent (DagNode): Parent to resulting shape node
        points (list): One tuples per point, with 3 floats each
        degree (int, optional): Degree of curve, 1 is linear
        form (int, optional): Whether to close the curve or not

    Example:
        >>> parent = createNode("transform")
        >>> shape = curve(parent, [
        ...     (0, 0, 0),
        ...     (0, 1, 0),
        ...     (0, 2, 0),
        ... ])
        ...

    """

    assert isinstance(parent, DagNode), (
        "parent must be of type cmdx.DagNode"
    )

    assert parent._modifier is None or parent._modifier.isDone, (
        "curve() currently doesn't work with a modifier"
    )

    # Superimpose end knots
    # startpoints = [points[0]] * (degree - 1)
    # endpoints = [points[-1]] * (degree - 1)
    # points = startpoints + list(points) + endpoints

    degree = min(3, max(1, degree))

    cvs = om1.MPointArray()
    knots = om1.MDoubleArray()
    curveFn = om1.MFnNurbsCurve()

    knotcount = len(points) - degree + 2 * degree - 1

    for point in points:
        cvs.append(om1.MPoint(*point))

    for index in range(knotcount):
        knots.append(index)

    mobj = curveFn.create(cvs,
                          knots,
                          degree,
                          form,
                          False,
                          True,
                          _encode1(parent.path()))

    mod = om1.MDagModifier()
    mod.renameNode(mobj, parent.name(namespace=True) + "Shape")
    mod.doIt()

    def undo():
        mod.deleteNode(mobj)
        mod.doIt()

    def redo():
        mod.undoIt()

    commit(undo, redo)

    shapeFn = om1.MFnDagNode(mobj)
    return encode(shapeFn.fullPathName())


def lookAt(origin, center, up=None):
    """Build a (left-handed) look-at matrix

    See glm::glc::matrix_transform::lookAt for reference

             + Z (up)
            /
           /
    (origin) o------ + X (center)
           \
            + Y

    Arguments:
        origin (Vector): Starting position
        center (Vector): Point towards this
        up (Vector, optional): Up facing this way, defaults to Y-up

    Example:
        >>> mat = lookAt(
        ...   (0, 0, 0),  # Relative the origin..
        ...   (1, 0, 0),  # X-axis points towards global X
        ...   (0, 1, 0)   # Z-axis points towards global Y
        ... )
        >>> tm = Tm(mat)
        >>> int(degrees(tm.rotation().x))
        -90

    """

    if isinstance(origin, (tuple, list)):
        origin = Vector(origin)

    if isinstance(center, (tuple, list)):
        center = Vector(center)

    if up is not None and isinstance(up, (tuple, list)):
        up = Vector(up)

    up = up or Vector(0, 1, 0)

    x = (center - origin).normalize()
    y = ((center - origin) ^ (center - up)).normalize()
    z = x ^ y

    return MatrixType((
        x[0], x[1], x[2], 0,
        y[0], y[1], y[2], 0,
        z[0], z[1], z[2], 0,
        0, 0, 0, 0
    ))


if ENABLE_PEP8:
    look_at = lookAt


def first(iterator, default=None):
    """Return first member of an `iterator`

    Example:
        >>> def it():
        ...   yield 1
        ...   yield 2
        ...   yield 3
        ...
        >>> first(it())
        1

    """

    return next(iterator, default)


def last(iterator, default=None):
    """Return last member of an `iterator`

    Example:
        >>> def it():
        ...   yield 1
        ...   yield 2
        ...   yield 3
        ...
        >>> last(it())
        3

    """

    last = default
    for member in iterator:
        last = member
    return last

# --------------------------------------------------------
#
# Attribute Types
#
# --------------------------------------------------------


class _AbstractAttribute(dict):
    Fn = None
    Type = None
    Default = None

    Readable = True
    Writable = True
    Cached = True  # Cache in datablock?
    Storable = True  # Write value to file?
    Hidden = False  # Display in Attribute Editor?

    Array = False
    Connectable = True

    Keyable = True
    ChannelBox = False
    AffectsAppearance = False
    AffectsWorldSpace = False

    Help = ""

    def __eq__(self, other):
        try:
            # Support Attribute -> Attribute comparison
            return self["name"] == other["name"]
        except AttributeError:
            # Support Attribute -> string comparison
            return self["name"] == other

    def __ne__(self, other):
        try:
            return self["name"] != other["name"]
        except AttributeError:
            return self["name"] != other

    def __hash__(self):
        """Support storing in set()"""
        return hash(self["name"])

    def __repr__(self):
        """Avoid repr depicting the full contents of this dict"""
        return self["name"]

    def __new__(cls, *args, **kwargs):
        """Support for using name of assignment

        Example:
            node["thisName"] =  cmdx.Double()

        In this example, the attribute isn't given a `name`
        Instead, the name is inferred from where it is assigned.

        """

        if not args:
            return cls, kwargs

        return super(_AbstractAttribute, cls).__new__(cls, *args, **kwargs)

    def __init__(self,
                 name,
                 default=None,
                 label=None,

                 writable=None,
                 readable=None,
                 cached=None,
                 storable=None,
                 keyable=None,
                 hidden=None,
                 min=None,
                 max=None,
                 channelBox=None,
                 affectsAppearance=None,
                 affectsWorldSpace=None,
                 array=False,
                 connectable=True,
                 help=None):

        args = locals().copy()
        args.pop("self")

        self["name"] = args.pop("name")
        self["label"] = args.pop("label")
        self["default"] = args.pop("default")

        # Exclusive to numeric attributes
        self["min"] = args.pop("min")
        self["max"] = args.pop("max")

        # Filled in on creation
        self["mobject"] = None

        # MyName -> myName
        self["shortName"] = self["name"][0].lower() + self["name"][1:]

        for key, value in args.items():
            default = getattr(self, key[0].upper() + key[1:])
            self[key] = value if value is not None else default

    def default(self, cls=None):
        """Return one of three available values

        Resolution order:
            1. Argument
            2. Node default (from cls.defaults)
            3. Attribute default

        """

        if self["default"] is not None:
            return self["default"]

        if cls is not None:
            return cls.defaults.get(self["name"], self.Default)

        return self.Default

    def type(self):
        return self.Type

    def create(self, cls=None):
        args = [
            arg
            for arg in (self["name"],
                        self["shortName"],
                        self.type())
            if arg is not None
        ]

        default = self.default(cls)
        if default:
            if isinstance(default, (list, tuple)):
                args += default
            else:
                args += [default]

        self["mobject"] = self.Fn.create(*args)

        # 3 μs
        self.Fn.storable = self["storable"]
        self.Fn.readable = self["readable"]
        self.Fn.writable = self["writable"]
        self.Fn.connectable = self["connectable"]
        self.Fn.hidden = self["hidden"]
        self.Fn.cached = self["cached"]
        self.Fn.keyable = self["keyable"]
        self.Fn.channelBox = self["channelBox"]
        self.Fn.affectsAppearance = self["affectsAppearance"]
        self.Fn.affectsWorldSpace = self["affectsWorldSpace"]
        self.Fn.array = self["array"]

        if self["min"] is not None:
            self.Fn.setMin(self["min"])

        if self["max"] is not None:
            self.Fn.setMax(self["max"])

        if self["label"] is not None:
            self.Fn.setNiceNameOverride(self["label"])

        return self["mobject"]

    def read(self, data):
        pass


class Enum(_AbstractAttribute):
    Fn = om.MFnEnumAttribute()
    Type = None
    Default = 0

    Keyable = True

    def __init__(self, name, fields=None, default=0, label=None, **kwargs):
        super(Enum, self).__init__(name, default, label, **kwargs)

        self.update({
            "fields": fields or (name,),
        })

    def create(self, cls=None):
        attr = super(Enum, self).create(cls)

        for index, field in enumerate(self["fields"]):
            self.Fn.addField(field, index)

        return attr

    def read(self, data):
        return data.inputValue(self["mobject"]).asShort()


class Divider(Enum):
    """Visual divider in channel box"""

    def __init__(self, label):
        super(Divider, self).__init__("_", fields=(label,), label=" ")


class String(_AbstractAttribute):
    Fn = om.MFnTypedAttribute()
    Type = om.MFnData.kString
    Default = ""

    def default(self, cls=None):
        default = str(super(String, self).default(cls))
        return om.MFnStringData().create(default)

    def read(self, data):
        return data.inputValue(self["mobject"]).asString()


class Message(_AbstractAttribute):
    Fn = om.MFnMessageAttribute()
    Type = None
    Default = None
    Storable = False


class Matrix(_AbstractAttribute):
    Fn = om.MFnMatrixAttribute()

    Default = (0.0,) * 4 * 4  # Identity matrix

    Array = False
    Readable = True
    Keyable = False
    Hidden = False

    def default(self, cls=None):
        return None

    def read(self, data):
        return data.inputValue(self["mobject"]).asMatrix()


class Long(_AbstractAttribute):
    Fn = om.MFnNumericAttribute()
    Type = om.MFnNumericData.kLong
    Default = 0

    def read(self, data):
        return data.inputValue(self["mobject"]).asLong()


class Double(_AbstractAttribute):
    Fn = om.MFnNumericAttribute()
    Type = om.MFnNumericData.kDouble
    Default = 0.0

    def read(self, data):
        return data.inputValue(self["mobject"]).asDouble()


class Double3(_AbstractAttribute):
    Fn = om.MFnNumericAttribute()
    Type = None
    Default = (0.0,) * 3

    def default(self, cls=None):
        if self["default"] is not None:
            default = self["default"]

            # Support single-value default
            if not isinstance(default, (tuple, list)):
                default = (default,) * 3

        elif cls is not None:
            default = cls.defaults.get(self["name"], self.Default)

        else:
            default = self.Default

        children = list()
        for index, child in enumerate("XYZ"):
            attribute = self.Fn.create(self["name"] + child,
                                       self["shortName"] + child,
                                       om.MFnNumericData.kDouble,
                                       default[index])
            children.append(attribute)

        return children

    def read(self, data):
        return data.inputValue(self["mobject"]).asDouble3()


class Boolean(_AbstractAttribute):
    Fn = om.MFnNumericAttribute()
    Type = om.MFnNumericData.kBoolean
    Default = True

    def read(self, data):
        return data.inputValue(self["mobject"]).asBool()


class AbstractUnit(_AbstractAttribute):
    Fn = om.MFnUnitAttribute()
    Default = 0.0
    Min = None
    Max = None
    SoftMin = None
    SoftMax = None


class Angle(AbstractUnit):
    def default(self, cls=None):
        default = super(Angle, self).default(cls)

        # When no unit was explicitly passed, assume degrees
        if not isinstance(default, om.MAngle):
            default = om.MAngle(default, om.MAngle.kDegrees)

        return default


class Time(AbstractUnit):
    def default(self, cls=None):
        default = super(Time, self).default(cls)

        # When no unit was explicitly passed, assume seconds
        if not isinstance(default, om.MTime):
            default = om.MTime(default, om.MTime.kSeconds)

        return default


class Distance(AbstractUnit):
    def default(self, cls=None):
        default = super(Distance, self).default(cls)

        # When no unit was explicitly passed, assume centimeters
        if not isinstance(default, om.MDistance):
            default = om.MDistance(default, om.MDistance.kCentimeters)

        return default


class Compound(_AbstractAttribute):
    Fn = om.MFnCompoundAttribute()
    Multi = None

    def __init__(self, name, children=None, **kwargs):
        if not children and self.Multi:
            default = kwargs.pop("default", None)
            children, Type = self.Multi
            children = tuple(
                Type(name + child, default=default[index], **kwargs)
                if default else Type(name + child, **kwargs)
                for index, child in enumerate(children)
            )

            self["children"] = children

        else:
            self["children"] = children

        super(Compound, self).__init__(name, **kwargs)

    def default(self, cls=None):
        # Compound itself has no defaults, only it's children do
        pass

    def create(self, cls=None):
        mobj = super(Compound, self).create(cls)
        default = super(Compound, self).default(cls)

        for index, child in enumerate(self["children"]):
            # Forward attributes from parent to child
            for attr in ("storable",
                         "readable",
                         "writable",
                         "hidden",
                         "channelBox",
                         "keyable",
                         "array"):
                child[attr] = self[attr]

            if child["default"] is None and default is not None:
                child["default"] = default[index]

            self.Fn.addChild(child.create(cls))

        return mobj

    def read(self, handle):
        """Read from MDataHandle"""
        output = list()

        for child in self["children"]:
            child_handle = handle.child(child["mobject"])
            output.append(child.read(child_handle))

        return tuple(output)


class Double2(Compound):
    Multi = ("XY", Double)


class Double4(Compound):
    Multi = ("XYZW", Double)


class Angle2(Compound):
    Multi = ("XY", Angle)


class Angle3(Compound):
    Multi = ("XYZ", Angle)


class Distance2(Compound):
    Multi = ("XY", Distance)


class Distance3(Compound):
    Multi = ("XYZ", Distance)


class Distance4(Compound):
    Multi = ("XYZW", Distance)


# --------------------------------------------------------
#
# Undo/Redo Support
#
# NOTE: Localised version of apiundo.py 0.2.0
# https://github.com/mottosso/apiundo
#
# In Maya, history is maintained by "commands". Each command is an instance of
# MPxCommand that encapsulates a series of API calls coupled with their
# equivalent undo/redo API calls. For example, the `createNode` command
# is presumably coupled with `cmds.delete`, `setAttr` is presumably
# coupled with another `setAttr` with the previous values passed in.
#
# Thus, creating a custom command involves subclassing MPxCommand and
# implementing coupling your do, undo and redo into one neat package.
#
# cmdx however doesn't fit into this framework.
#
# With cmdx, you call upon API calls directly. There is little to no
# correlation between each of your calls, which is great for performance
# but not so great for conforming to the undo/redo framework set forth
# by Autodesk.
#
# To work around this, without losing out on performance or functionality,
# a generic command is created, capable of hosting arbitrary API calls
# and storing them in the Undo/Redo framework.
#
#   >>> node = cmdx.createNode("transform")
#   >>> cmdx.commit(lambda: cmdx.delete(node))
#
# Now when you go to undo, the `lambda` is called. It is then up to you
# the developer to ensure that what is being undone actually relates
# to what you wanted to have undone. For example, it is perfectly
# possible to add an unrelated call to history.
#
#   >>> node = cmdx.createNode("transform")
#   >>> cmdx.commit(lambda: cmdx.setAttr(node + "translateX", 5))
#
# The result would be setting an attribute to `5` when attempting to undo.
#
# --------------------------------------------------------


# Support for multiple co-existing versions of apiundo.
# NOTE: This is important for vendoring, as otherwise a vendored apiundo
# could register e.g. cmds.apiUndo() first, causing a newer version
# to inadvertently use this older command (or worse yet, throwing an
# error when trying to register it again).
command = "_cmdxApiUndo_%s" % __version__.replace(".", "_")

# This module is both a Python module and Maya plug-in.
# Data is shared amongst the two through this "module"
name = "_cmdxShared_"
if name not in sys.modules:
    sys.modules[name] = types.ModuleType(name)

shared = sys.modules[name]
shared.undo = None
shared.redo = None
shared.undos = {}
shared.redos = {}


def commit(undo, redo=lambda: None):
    """Commit `undo` and `redo` to history

    Arguments:
        undo (func): Call this function on next undo
        redo (func, optional): Like `undo`, for for redo

    """

    if not ENABLE_UNDO:
        return

    if not hasattr(cmds, command):
        install()

    # Precautionary measure.
    # If this doesn't pass, odds are we've got a race condition.
    # NOTE: This assumes calls to `commit` can only be done
    # from a single thread, which should already be the case
    # given that Maya's API is not threadsafe.
    try:
        assert shared.redo is None
        assert shared.undo is None
    except AssertionError:
        log.debug("%s has a problem with undo" % __name__)

    # Temporarily store the functions at shared-level,
    # they are later picked up by the command once called.
    shared.undo = "%x" % id(undo)
    shared.redo = "%x" % id(redo)
    shared.undos[shared.undo] = undo
    shared.redos[shared.redo] = redo

    # Let Maya know that something is undoable
    getattr(cmds, command)()


def install():
    """Load this shared as a plug-in

    Call this prior to using the shared

    """

    if ENABLE_UNDO:
        cmds.loadPlugin(__file__, quiet=True)

    self.installed = True


def uninstall():
    if ENABLE_UNDO:
        # Plug-in may exist in undo queue and
        # therefore cannot be unloaded until flushed.
        cmds.flushUndo()

        # Discard shared module
        shared.undo = None
        shared.redo = None
        shared.undos.clear()
        shared.redos.clear()
        sys.modules.pop(name, None)

        cmds.unloadPlugin(os.path.basename(__file__))

    self.installed = False


def maya_useNewAPI():
    pass


class _apiUndo(om.MPxCommand):
    def doIt(self, args):
        self.undo = shared.undo
        self.redo = shared.redo

        # Facilitate the above precautionary measure
        shared.undo = None
        shared.redo = None

    def undoIt(self):
        shared.undos[self.undo]()

    def redoIt(self):
        shared.redos[self.redo]()

    def isUndoable(self):
        # Without this, the above undoIt and redoIt will not be called
        return True


def initializePlugin(plugin):
    om.MFnPlugin(plugin).registerCommand(
        command,
        _apiUndo
    )


def uninitializePlugin(plugin):
    om.MFnPlugin(plugin).deregisterCommand(command)


# --------------------------------------------------------
#
# Commonly Node Types
#
# Creating a new node using a pre-defined Type ID is 10% faster
# than doing it using a string, but keeping all (~800) around
# has a negative impact on maintainability and readability of
# the project, so a balance is struck where only the most
# performance sensitive types are included here.
#
# Developers: See cmdt.py for a list of all available types and their IDs
#
# --------------------------------------------------------


tAddDoubleLinear = om.MTypeId(0x4441444c)
tAddMatrix = om.MTypeId(0x44414d58)
tAngleBetween = om.MTypeId(0x4e414254)
tBlendShape = om.MTypeId(0x46424c53)
tMultMatrix = om.MTypeId(0x444d544d)
tAngleDimension = om.MTypeId(0x4147444e)
tBezierCurve = om.MTypeId(0x42435256)
tCamera = om.MTypeId(0x4443414d)
tChoice = om.MTypeId(0x43484345)
tChooser = om.MTypeId(0x43484f4f)
tCondition = om.MTypeId(0x52434e44)
tMesh = om.MTypeId(0x444d5348)
tNurbsCurve = om.MTypeId(0x4e435256)
tNurbsSurface = om.MTypeId(0x4e535246)
tJoint = om.MTypeId(0x4a4f494e)
tTransform = om.MTypeId(0x5846524d)
tTransformGeometry = om.MTypeId(0x5447454f)
tWtAddMatrix = om.MTypeId(0x4457414d)


# --------------------------------------------------------
#
# Plug-ins
#
# --------------------------------------------------------

InstalledPlugins = dict()
TypeId = om.MTypeId

# Get your unique ID from Autodesk, the below
# should not be trusted for production.
StartId = int(os.getenv("CMDX_BASETYPEID", "0x12b9c0"), 0)


class MetaNode(type):
    def __init__(cls, *args, **kwargs):
        assert isinstance(cls.name, str)
        assert isinstance(cls.defaults, dict)
        assert isinstance(cls.attributes, list)
        assert isinstance(cls.version, tuple)

        if isinstance(cls.typeid, (int, float)):
            cls.typeid = TypeId(cls.typeid)

        # Support Divider plug-in, without name for readability.
        # E.g. Divider("_", "Label") -> Divider("Label")
        index = 1
        for attribute in cls.attributes:
            if isinstance(attribute, Divider):
                attribute["name"] = "_" * index
                attribute["shortName"] = "_" * index
                index += 1

        # Ensure no duplicates
        assert len(set(cls.attributes)) == len(cls.attributes), (
            "One or more attributes in '%s' was found more than once"
            % cls.__name__
        )

        attributes = {attr["name"]: attr for attr in cls.attributes}

        def findAttribute(self, name):
            return attributes.get(name)

        def findMObject(self, name):
            return attributes.get(name)["mobject"]

        def findPlug(self, node, name):
            try:
                mobj = attributes.get(name)["mobject"]
                return om.MPlug(node, mobj)
            except KeyError:
                return None

        cls.findAttribute = findAttribute
        cls.findMObject = findMObject
        cls.findPlug = findPlug

        cls.find_attribute = findAttribute
        cls.find_mobject = findMObject
        cls.find_plug = findPlug

        cls.log = logging.getLogger(cls.__name__)

        return super(MetaNode, cls).__init__(*args, **kwargs)


class DgNode(om.MPxNode):
    """Abstract baseclass for a Maya DG node

    Attributes:
        name (str): Name used in e.g. cmds.createNode
        id (int): Unique ID from Autodesk (see Ids above)
        version (tuple, optional): Optional version number for plug-in node
        attributes (tuple, optional): Attributes of node
        defaults (dict, optional): Dictionary of default values

    """

    __metaclass__ = MetaNode

    typeid = TypeId(StartId)
    name = "defaultNode"
    version = (0, 0)
    attributes = list()
    affects = list()
    ranges = dict()
    defaults = {}

    @classmethod
    def postInitialize(cls):
        pass


class SurfaceShape(om.MPxSurfaceShape):
    """Abstract baseclass for a Maya shape

    Attributes:
        name (str): Name used in e.g. cmds.createNode
        id (int): Unique ID from Autodesk (see Ids above)
        version (tuple, optional): Optional version number for plug-in node
        attributes (tuple, optional): Attributes of node
        defaults (dict, optional): Dictionary of default values

    """

    __metaclass__ = MetaNode

    typeid = TypeId(StartId)
    classification = "drawdb/geometry/custom"
    name = "defaultNode"
    version = (0, 0)
    attributes = list()
    affects = list()
    ranges = dict()
    defaults = {}

    @classmethod
    def postInitialize(cls):
        pass

    @classmethod
    def uiCreator(cls):
        pass


class SurfaceShapeUI(omui.MPxSurfaceShapeUI):
    """Abstract baseclass for a Maya shape

    Attributes:
        name (str): Name used in e.g. cmds.createNode
        id (int): Unique ID from Autodesk (see Ids above)
        version (tuple, optional): Optional version number for plug-in node
        attributes (tuple, optional): Attributes of node
        defaults (dict, optional): Dictionary of default values

    """

    __metaclass__ = MetaNode

    typeid = TypeId(StartId)
    classification = "drawdb/geometry/custom"
    name = "defaultNode"
    version = (0, 0)
    attributes = list()
    affects = list()
    ranges = dict()
    defaults = {}

    @classmethod
    def postInitialize(cls):
        pass


class LocatorNode(omui.MPxLocatorNode):
    """Abstract baseclass for a Maya locator

    Attributes:
        name (str): Name used in e.g. cmds.createNode
        id (int): Unique ID from Autodesk (see Ids above)
        version (tuple, optional): Optional version number for plug-in node
        attributes (tuple, optional): Attributes of node
        defaults (dict, optional): Dictionary of default values

    """

    __metaclass__ = MetaNode

    name = "defaultNode"
    typeid = TypeId(StartId)
    classification = "drawdb/geometry/custom"
    version = (0, 0)
    attributes = list()
    affects = list()
    ranges = dict()
    defaults = {}

    @classmethod
    def postInitialize(cls):
        pass


def initialize2(Plugin):
    def _nodeInit():
        nameToAttr = {}
        for attr in Plugin.attributes:
            mattr = attr.create(Plugin)
            Plugin.addAttribute(mattr)
            nameToAttr[attr["name"]] = mattr

        for src, dst in Plugin.affects:
            log.debug("'%s' affects '%s'" % (src, dst))
            Plugin.attributeAffects(nameToAttr[src], nameToAttr[dst])

    def _nodeCreator():
        return Plugin()

    def initializePlugin(obj):
        version = ".".join(map(str, Plugin.version))
        plugin = om.MFnPlugin(obj, "Cmdx", version, "Any")

        try:
            if issubclass(Plugin, LocatorNode):
                plugin.registerNode(Plugin.name,
                                    Plugin.typeid,
                                    _nodeCreator,
                                    _nodeInit,
                                    om.MPxNode.kLocatorNode,
                                    Plugin.classification)

            elif issubclass(Plugin, DgNode):
                plugin.registerNode(Plugin.name,
                                    Plugin.typeid,
                                    _nodeCreator,
                                    _nodeInit)

            elif issubclass(Plugin, SurfaceShape):
                plugin.registerShape(Plugin.name,
                                     Plugin.typeid,
                                     _nodeCreator,
                                     _nodeInit,
                                     Plugin.uiCreator,
                                     Plugin.classification)

            else:
                raise TypeError("Unsupported subclass: '%s'" % Plugin)

        except Exception:
            raise

        else:
            # Maintain reference to original class
            InstalledPlugins[Plugin.name] = Plugin

            Plugin.postInitialize()

    return initializePlugin


def uninitialize2(Plugin):
    def uninitializePlugin(obj):
        om.MFnPlugin(obj).deregisterNode(Plugin.typeid)

    return uninitializePlugin


# Plugins written with Maya Python API 1.0

class MPxManipContainer1(ompx1.MPxManipContainer):
    name = "defaultManip"
    version = (0, 0)
    ownerid = om1.MTypeId(StartId)
    typeid = om1.MTypeId(StartId)


def initializeManipulator1(Manipulator):
    def _manipulatorCreator():
        return ompx1.asMPxPtr(Manipulator())

    def _manipulatorInit():
        ompx1.MPxManipContainer.addToManipConnectTable(Manipulator.ownerid)
        ompx1.MPxManipContainer.initialize()

    def initializePlugin(obj):
        version = ".".join(map(str, Manipulator.version))
        plugin = ompx1.MFnPlugin(obj, "Cmdx", version, "Any")

        # NOTE(marcus): The name *must* end with Manip
        # See https://download.autodesk.com/us/maya/2011help
        #     /API/class_m_px_manip_container.html
        #     #e95527ff30ae53c8ae0419a1abde8b0c
        assert Manipulator.name.endswith("Manip"), (
            "Manipulator '%s' must have the name of a plug-in, "
            "and end with 'Manip'"
        )

        plugin.registerNode(
            Manipulator.name,
            Manipulator.typeid,
            _manipulatorCreator,
            _manipulatorInit,
            ompx1.MPxNode.kManipContainer
        )

    return initializePlugin


def uninitializeManipulator1(Manipulator):
    def uninitializePlugin(obj):
        ompx1.MFnPlugin(obj).deregisterNode(Manipulator.typeid)

    return uninitializePlugin


def findPlugin(name):
    """Find the original class of a plug-in by `name`"""

    try:
        return InstalledPlugins[name]
    except KeyError:
        raise ExistError("'%s' is not a recognised plug-in" % name)


# --------------------------
#
# Callback Manager
#
# --------------------------


class Callback(object):
    """A Maya callback"""

    log = logging.getLogger("cmdx.Callback")

    def __init__(self, name, installer, args, api=2, help="", parent=None):
        self._id = None
        self._args = args
        self._name = name
        self._installer = installer
        self._help = help

        # Callbacks are all uninstalled using the same function
        # relative either API 1.0 or 2.0
        self._uninstaller = {
            1: om1.MMessage.removeCallback,
            2: om.MMessage.removeCallback
        }[api]

    def __del__(self):
        self.deactivate()

    def name(self):
        return self._name

    def help(self):
        return self._help

    def is_active(self):
        return self._id is not None

    def activate(self):
        self.log.debug("Activating callback '%s'.." % self._name)

        if self.is_active():
            self.log.debug("%s already active, ignoring" % self._name)
            return

        self._id = self._installer(*self._args)

    def deactivate(self):
        self.log.debug("Deactivating callback '%s'.." % self._name)

        if self.is_active():
            self._uninstaller(self._id)

        self._id = None


class CallbackGroup(list):
    """Multiple callbacks rolled into one"""

    def __init__(self, name, callbacks, parent=None):
        self._name = name
        self[:] = callbacks

    def name(self):
        return self._name

    def add(self, name, installer, args, api=2):
        """Convenience method for .append(Callback())"""
        callback = Callback(name, installer, args, api)
        self.append(callback)

    def activate(self):
        for callback in self._callbacks:
            callback.activate()

    def deactivate(self):
        for callback in self._callbacks:
            callback.deactivate()


# ----------------------
#
# Cache Manager
#
# ----------------------

class Cache(object):
    def __init__(self):
        self._values = {}

    def clear(self, node=None):
        pass

    def read(self, node, attr, time):
        pass

    def transform(self, node):
        pass

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#    http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.