[FAB-9940] add "seek from" support for deliveryevent

Currently only "seek from last" is supported. Some low level
support from "seek from block" exists. Add the scaffolding
and external api to expose that.

Change-Id: I9937d8d2cf11851e2d41b69555887aaa1a50e3ff
Signed-off-by: Srinivasan Muralidharan <srinivasan.muralidharan99@gmail.com>

pkg/client/event/event.go

@@ -18,13 +18,17 @@ import (
 	"github.com/hyperledger/fabric-sdk-go/pkg/common/providers/context"
 	"github.com/hyperledger/fabric-sdk-go/pkg/common/providers/fab"
 	"github.com/hyperledger/fabric-sdk-go/pkg/fab/events/client"
+	"github.com/hyperledger/fabric-sdk-go/pkg/fab/events/deliverclient"
+	"github.com/hyperledger/fabric-sdk-go/pkg/fab/events/deliverclient/seek"
 	"github.com/pkg/errors"
 )
 
 // Client enables access to a channel events on a Fabric network.
 type Client struct {
 	eventService      fab.EventService
 	permitBlockEvents bool
+	fromBlock         uint64
+	seekType          seek.Type
 }
 
 // New returns a Client instance. Client receives events such as block, filtered block,
@@ -51,7 +55,7 @@ func New(channelProvider context.ChannelProvider, opts ...ClientOption) (*Client
 
 	var es fab.EventService
 	if eventClient.permitBlockEvents {
-		es, err = channelContext.ChannelService().EventService(client.WithBlockEvents())
+		es, err = channelContext.ChannelService().EventService(client.WithBlockEvents(), deliverclient.WithSeekType(eventClient.seekType), deliverclient.WithBlockNum(eventClient.fromBlock))
 	} else {
 		es, err = channelContext.ChannelService().EventService()
 	}

pkg/client/event/event_test.go

@@ -6,6 +6,7 @@ SPDX-License-Identifier: Apache-2.0
 package event
 
 import (
+	"math"
 	"testing"
 	"time"
 
@@ -19,6 +20,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/stretchr/testify/assert"
 
+	"github.com/hyperledger/fabric-sdk-go/pkg/fab/events/deliverclient/seek"
 	"github.com/hyperledger/fabric-sdk-go/pkg/fab/events/service"
 	"github.com/hyperledger/fabric-sdk-go/pkg/fab/events/service/dispatcher"
 	servicemocks "github.com/hyperledger/fabric-sdk-go/pkg/fab/events/service/mocks"
@@ -41,7 +43,7 @@ func TestNewEventClient(t *testing.T) {
 		t.Fatalf("Failed to create new event client: %s", err)
 	}
 
-	_, err = New(ctx, WithBlockEvents())
+	_, err = New(ctx, WithBlockEvents(), WithSeekType(seek.Newest), WithBlockNum(math.MaxUint64))
 	if err != nil {
 		t.Fatalf("Failed to create new event client: %s", err)
 	}

pkg/client/event/opts.go

@@ -6,6 +6,8 @@ SPDX-License-Identifier: Apache-2.0
 
 package event
 
+import "github.com/hyperledger/fabric-sdk-go/pkg/fab/events/deliverclient/seek"
+
 // ClientOption describes a functional parameter for the New constructor
 type ClientOption func(*Client) error
 
@@ -17,3 +19,21 @@ func WithBlockEvents() ClientOption {
 		return nil
 	}
 }
+
+// WithBlockNum indicates the block number from which events are to be received.
+// Only deliverclient supports this
+func WithBlockNum(from uint64) ClientOption {
+	return func(c *Client) error {
+		c.fromBlock = from
+		return nil
+	}
+}
+
+// WithSeekType indicates the  type of seek desired - newest, oldest or from given block
+// Only deliverclient supports this
+func WithSeekType(seek seek.Type) ClientOption {
+	return func(c *Client) error {
+		c.seekType = seek
+		return nil
+	}
+}

test/integration/sdk/events_client_test.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/hyperledger/fabric-sdk-go/pkg/client/channel"
 	"github.com/hyperledger/fabric-sdk-go/pkg/client/event"
+	"github.com/hyperledger/fabric-sdk-go/pkg/fab/events/deliverclient/seek"
 	"github.com/hyperledger/fabric-sdk-go/pkg/fabsdk"
 	"github.com/hyperledger/fabric-sdk-go/test/integration"
 )
@@ -35,7 +36,7 @@ func TestDefaultEventClient(t *testing.T) {
 	}
 
 	// get default event client (with filtered block events)
-	eventClient, err := event.New(org1ChannelClientContext)
+	eventClient, err := event.New(org1ChannelClientContext, event.WithSeekType(seek.Newest))
 	if err != nil {
 		t.Fatalf("Failed to create new events client: %s", err)
 	}
@@ -70,7 +71,7 @@ func TestEventsClientWithBlockEvents(t *testing.T) {
 	}
 
 	// create event client with block events
-	eventClient, err := event.New(org1ChannelClientContext, event.WithBlockEvents())
+	eventClient, err := event.New(org1ChannelClientContext, event.WithBlockEvents(), event.WithSeekType(seek.Newest))
 	if err != nil {
 		t.Fatalf("Failed to create new events client with block events: %s", err)
 	}