From a00bc520df4f6e41176347004eccf64f6ab4b490 Mon Sep 17 00:00:00 2001
From: Peter Portante <peter.portante@redhat.com>
Date: Fri, 28 Apr 2017 10:07:22 -0400
Subject: [PATCH] Here is one example of abstaction hiding

This examples uses a "proxy" class.  It is specifically not functional
as I left a bug in it.  Can you see how it hides the mechanism from the
caller while reducing the line count.

Change-Id: Ia0738bfe8b0450f6da8f2bf88d436fc738033e8f
---
 lib/Quads.py                               | 27 +++-------------
 lib/hardware_services/inventory_service.py | 36 ++++++++++-----------
 lib/hardware_services/network_service.py   | 37 ++++++++++------------
 3 files changed, 36 insertions(+), 64 deletions(-)

diff --git a/lib/Quads.py b/lib/Quads.py
index dda600dcb..b91dc3f87 100755
--- a/lib/Quads.py
+++ b/lib/Quads.py
@@ -28,10 +28,8 @@
 import urllib
 import json
 from subprocess import check_call
-from hardware_services.inventory_service import get_inventory_service, set_inventory_service
-from hardware_services.network_service import get_network_service, set_network_service
-sys.path.append(os.path.dirname(__file__) + "/hardware_services/inventory_drivers/")
-sys.path.append(os.path.dirname(__file__) + "/hardware_services/network_drivers/")
+from hardware_services.inventory_service import InventoryServiceProxy
+from hardware_services.network_service import NetworkServiceProxy
 
 
 class Quads(object):
@@ -47,21 +45,8 @@ def __init__(self, config, statedir, movecommand, datearg, syncstate, initialize
         self.logger = logging.getLogger("quads.Quads")
         self.logger.setLevel(logging.DEBUG)
 
-        #EC528 addition - dynamically import driver module and set inventory and network services
-        inventoryservice = hardwareservice + "InventoryDriver"
-        networkservice = hardwareservice + "NetworkDriver"
-
-        importlib.import_module(inventoryservice)
-        importlib.import_module(networkservice)
-
-        set_inventory_service(getattr(sys.modules[inventoryservice], inventoryservice)())
-        set_network_service(getattr(sys.modules[networkservice], networkservice)())
-
-        self.inventory_service = get_inventory_service()
-        self.network_service = get_network_service()
-
-        self.hardware_service_url = hardwareserviceurl
-
+        self.inventory_service = InventoryServiceProxy(hardwareservice, hardwarewserviceurl)
+        self.network_service = NetworkServiceProxy(hardwareservice, hardwareserviceurl)
 
         self.inventory_service.load_data(self, force, initialize)
 
@@ -616,7 +601,3 @@ def quads_get(self, url, params=None):
     @classmethod
     def quads_delete(self, url):
         self.quads_status_code_check(requests.delete(url))
-
-
-
-
diff --git a/lib/hardware_services/inventory_service.py b/lib/hardware_services/inventory_service.py
index 78379e740..9c1b02fc7 100755
--- a/lib/hardware_services/inventory_service.py
+++ b/lib/hardware_services/inventory_service.py
@@ -32,9 +32,24 @@
 # will be able to continue with minimal changes (only thing that this will change is where QUADS pulls its data from)
 #####################################################################################################################
 
-import sys
+import os, sys, importlib
 from abc import ABCMeta, abstractmethod
 
+
+sys.path.append(os.path.dirname(__file__) + "/hardware_services/inventory_drivers/")
+
+
+class InventoryServiceProxy(object):
+    def __init__(self, name):
+        self.name = name
+        inventoryservice = name + "InventoryDriver"
+        importlib.import_module()
+        self.invsrv = getattr(sys.modules[inventoryservice], inventoryservice)()
+
+    def __getattr__(self, attr_name):
+        return getattr(self.invsrv, attr_name)
+
+
 class InventoryService(object):
 
     __metaclass__ = ABCMeta
@@ -88,22 +103,3 @@ def sync_state(self, quads):
     def write_data(self, quads, doexit):
         """ TODO add documentation
         """
-
-
-_inventory_service = None
-
-
-def set_inventory_service(inventory_service):
-
-    global _inventory_service
-    if _inventory_service is not None:
-        sys.exit("Error: _inventory_service already set")
-
-    _inventory_service = inventory_service
-
-
-def get_inventory_service():
-    return _inventory_service
-
-
-
diff --git a/lib/hardware_services/network_service.py b/lib/hardware_services/network_service.py
index 404bd6d86..3168487a8 100755
--- a/lib/hardware_services/network_service.py
+++ b/lib/hardware_services/network_service.py
@@ -32,34 +32,29 @@
 # will be able to continue with minimal changes (only thing that this will change is where QUADS pulls its data from)
 #####################################################################################################################
 
-import sys
+import os, sys, importlib
 from abc import ABCMeta, abstractmethod
 
-class NetworkService(object):
-
-    __metaclass__ = ABCMeta
-
-
-    @abstractmethod
-    def move_hosts(self, **kwargs):
-        """ TODO add documentation
-        """
 
+sys.path.append(os.path.dirname(__file__) + "/hardware_services/network_drivers/")
 
-_network_service = None
 
+class NetworkServiceProxy(object):
+    def __init__(self, name):
+        self.name = name
+        networkservice = name + "NetworkDriver"
+        importlib.import_module()
+        self.invsrv = getattr(sys.modules[networkservice], networkservice)()
 
-def set_network_service(network_service):
+    def __getattr__(self, attr_name):
+        return getattr(self.netsrv, attr_name)
 
-    global _network_service
-    if _network_service is not None:
-        sys.exit("Error: _network_service already set")
-
-    _network_service = network_service
-
-
-def get_network_service():
-    return _network_service
 
+class NetworkService(object):
 
+    __metaclass__ = ABCMeta
 
+    @abstractmethod
+    def move_hosts(self, **kwargs):
+        """ TODO add documentation
+        """