[FAB-8396] Abstract Event Client

Implement an abstract event client that
connects to a GRPC event server and manages
the connection/stream. This client may be
extended by protocol-specific implementations
(i.e. Event Hub and Deliver Service).

Also moved files to new package structure.

Change-Id: I489fd7e6c5780fda2e43412c8aadf732343b8e36
Signed-off-by: Bob Stasyszyn <Bob.Stasyszyn@securekey.com>

api/apifabclient/eventservice.go → pkg/context/api/fab/eventservice.go

@@ -4,7 +4,7 @@ Copyright SecureKey Technologies Inc. All Rights Reserved.
 SPDX-License-Identifier: Apache-2.0
 */
 
-package apifabclient
+package fab
 
 import (
 	cb "github.com/hyperledger/fabric-sdk-go/third_party/github.com/hyperledger/fabric/protos/common"
@@ -79,6 +79,16 @@ type EventService interface {
 	Unregister(reg Registration)
 }
 
+// ConnectionEvent is sent when the client disconnects from or
+// reconnects to the event server. Connected == true means that the
+// client has connected, whereas Connected == false means that the
+// client has disconnected. In the disconnected case, Err contains
+// the disconnect error.
+type ConnectionEvent struct {
+	Connected bool
+	Err       error
+}
+
 // EventClient is a client that connects to a peer and receives channel events
 // such as block, filtered block, chaincode, and transaction status events.
 type EventClient interface {
@@ -90,4 +100,9 @@ type EventClient interface {
 	// Close closes the connection to the event server and releases all resources.
 	// Once this function is invoked the client may no longer be used.
 	Close()
+
+	// RegisterConnectionEvent registers a connection event. The returned
+	// ConnectionEvent channel is called whenever the client clients to
+	// or disconnects from the event server
+	RegisterConnectionEvent() (Registration, chan ConnectionEvent, error)
 }

pkg/fab/events/api/connection.go

@@ -0,0 +1,25 @@
+/*
+Copyright SecureKey Technologies Inc. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package api
+
+import (
+	"github.com/hyperledger/fabric-sdk-go/pkg/context"
+	"github.com/hyperledger/fabric-sdk-go/pkg/context/api/fab"
+)
+
+// Connection defines the functions for an event server connection
+type Connection interface {
+	// Receive sends events to the given channel
+	Receive(chan<- interface{})
+	// Close closes the connection
+	Close()
+	// Closed return true if the connection is closed
+	Closed() bool
+}
+
+// ConnectionProvider creates a Connection.
+type ConnectionProvider func(channelID string, context context.Context, peer fab.Peer) (Connection, error)