KS-15 Add a capabilities library to the core node

core/capabilities/capability.go

@@ -0,0 +1,246 @@
+package capabilities
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"regexp"
+	"time"
+
+	"golang.org/x/mod/semver"
+
+	"github.com/smartcontractkit/chainlink-common/pkg/values"
+)
+
+// CapabilityType is an enum for the type of capability.
+type CapabilityType int
+
+// CapabilityType enum values.
+const (
+	CapabilityTypeTrigger CapabilityType = iota
+	CapabilityTypeAction
+	CapabilityTypeConsensus
+	CapabilityTypeTarget
+)
+
+// String returns a string representation of CapabilityType
+func (c CapabilityType) String() string {
+	switch c {
+	case CapabilityTypeTrigger:
+		return "trigger"
+	case CapabilityTypeAction:
+		return "action"
+	case CapabilityTypeConsensus:
+		return "report"
+	case CapabilityTypeTarget:
+		return "target"
+	}
+
+	// Panic as this should be unreachable.
+	panic("unknown capability type")
+}
+
+// IsValid checks if the capability type is valid.
+func (c CapabilityType) IsValid() error {
+	switch c {
+	case CapabilityTypeTrigger,
+		CapabilityTypeAction,
+		CapabilityTypeConsensus,
+		CapabilityTypeTarget:
+		return nil
+	}
+
+	return fmt.Errorf("invalid capability type: %s", c)
+}
+
+// CapabilityResponse is a struct for the Execute response of a capability.
+type CapabilityResponse struct {
+	Value values.Value
+	Err   error
+}
+
+type Metadata struct {
+	WorkflowID string
+}
+
+type CapabilityRequest struct {
+	Metadata Metadata
+	Config   *values.Map
+	Inputs   *values.Map
+}
+
+// CallbackExecutable is an interface for executing a capability.
+type CallbackExecutable interface {
+	// Capability must respect context.Done and cleanup any request specific resources
+	// when the context is cancelled. When a request has been completed the capability
+	// is also expected to close the callback channel.
+	// Request specific configuration is passed in via the inputs parameter.
+	// A successful response must always return a value. An error is assumed otherwise.
+	// The intent is to make the API explicit.
+	Execute(ctx context.Context, callback chan CapabilityResponse, request CapabilityRequest) error
+}
+
+// BaseCapability interface needs to be implemented by all capability types.
+// Capability interfaces are intentionally duplicated to allow for an easy change
+// or extension in the future.
+type BaseCapability interface {
+	Info() CapabilityInfo
+}
+
+// TriggerCapability interface needs to be implemented by all trigger capabilities.
+type TriggerCapability interface {
+	BaseCapability
+	RegisterTrigger(ctx context.Context, callback chan CapabilityResponse, request CapabilityRequest) error
+	UnregisterTrigger(ctx context.Context, request CapabilityRequest) error
+}
+
+// ActionCapability interface needs to be implemented by all action capabilities.
+type ActionCapability interface {
+	BaseCapability
+	CallbackExecutable
+}
+
+// ConsensusCapability interface needs to be implemented by all consensus capabilities.
+type ConsensusCapability interface {
+	BaseCapability
+	CallbackExecutable
+}
+
+// TargetsCapability interface needs to be implemented by all target capabilities.
+type TargetCapability interface {
+	BaseCapability
+	CallbackExecutable
+}
+
+// CapabilityInfo is a struct for the info of a capability.
+type CapabilityInfo struct {
+	ID             string
+	CapabilityType CapabilityType
+	Description    string
+	Version        string
+}
+
+// Info returns the info of the capability.
+func (c CapabilityInfo) Info() CapabilityInfo {
+	return c
+}
+
+var idRegex = regexp.MustCompile(`[a-z0-9_\-:]`)
+
+const (
+	// TODO: this length was largely picked arbitrarily.
+	// Consider what a realistic/desirable value should be.
+	// See: https://smartcontract-it.atlassian.net/jira/software/c/projects/KS/boards/182
+	idMaxLength = 128
+)
+
+// NewCapabilityInfo returns a new CapabilityInfo.
+func NewCapabilityInfo(
+	id string,
+	capabilityType CapabilityType,
+	description string,
+	version string,
+) (CapabilityInfo, error) {
+	if len(id) > idMaxLength {
+		return CapabilityInfo{}, fmt.Errorf("invalid id: %s exceeds max length %d", id, idMaxLength)
+	}
+	if !idRegex.MatchString(id) {
+		return CapabilityInfo{}, fmt.Errorf("invalid id: %s. Allowed: %s", id, idRegex)
+	}
+
+	if ok := semver.IsValid(version); !ok {
+		return CapabilityInfo{}, fmt.Errorf("invalid version: %+v", version)
+	}
+
+	if err := capabilityType.IsValid(); err != nil {
+		return CapabilityInfo{}, err
+	}
+
+	return CapabilityInfo{
+		ID:             id,
+		CapabilityType: capabilityType,
+		Description:    description,
+		Version:        version,
+	}, nil
+}
+
+// MustCapabilityInfo returns a new CapabilityInfo,
+// panicking if we could not instantiate a CapabilityInfo.
+func MustCapabilityInfo(
+	id string,
+	capabilityType CapabilityType,
+	description string,
+	version string,
+) CapabilityInfo {
+	c, err := NewCapabilityInfo(id, capabilityType, description, version)
+	if err != nil {
+		panic(err)
+	}
+
+	return c
+}
+
+// TODO: this timeout was largely picked arbitrarily.
+// Consider what a realistic/desirable value should be.
+// See: https://smartcontract-it.atlassian.net/jira/software/c/projects/KS/boards/182
+var defaultExecuteTimeout = 10 * time.Second
+
+// ExecuteSync executes a capability synchronously.
+// We are not handling a case where a capability panics and crashes.
+// There is default timeout of 10 seconds. If a capability takes longer than
+// that then it should be executed asynchronously.
+func ExecuteSync(ctx context.Context, c CallbackExecutable, request CapabilityRequest) (values.Value, error) {
+	ctxWithT, cancel := context.WithTimeout(ctx, defaultExecuteTimeout)
+	defer cancel()
+
+	callback := make(chan CapabilityResponse)
+	sec := make(chan error)
+
+	go func(innerCtx context.Context, innerC CallbackExecutable, innerReq CapabilityRequest, innerCallback chan CapabilityResponse, errCh chan error) {
+		setupErr := innerC.Execute(innerCtx, innerCallback, innerReq)
+		sec <- setupErr
+	}(ctxWithT, c, request, callback, sec)
+
+	vs := make([]values.Value, 0)
+outerLoop:
+	for {
+		select {
+		case response, isOpen := <-callback:
+			if !isOpen {
+				break outerLoop
+			}
+			// An error means execution has been interrupted.
+			// We'll return the value discarding values received
+			// until now.
+			if response.Err != nil {
+				return nil, response.Err
+			}
+
+			vs = append(vs, response.Value)
+
+		// Timeout when a capability panics, crashes, and does not close the channel.
+		case <-ctxWithT.Done():
+			return nil, fmt.Errorf("context timed out. If you did not set a timeout, be aware that the default ExecuteSync timeout is %f seconds", defaultExecuteTimeout.Seconds())
+		}
+	}
+
+	setupErr := <-sec
+	// Something went wrong when setting up a capability.
+	if setupErr != nil {
+		return nil, setupErr
+	}
+
+	// If the capability did not return any values, we deem it as an error.
+	// The intent is for the API to be explicit.
+	if len(vs) == 0 {
+		return nil, errors.New("capability did not return any values")
+	}
+
+	// If the capability returned only one value,
+	// let's unwrap it to improve usability.
+	if len(vs) == 1 {
+		return vs[0], nil
+	}
+
+	return &values.List{Underlying: vs}, nil
+}