fix(store): simplify cursor

docs/api/store.md

@@ -28,20 +28,15 @@ if err != nil {
     // Handle error ...
 }
 
-for {
+for !result.IsComplete() {
-    hasNext, err := result.Next(ctx)
-    if err != nil {
-        // Handle error ...
-        break
-    }
-
-    if !hasNext { // No more messages available
-        break
-    }
-
     for _, msg := range result.GetMessages() {
         // Do something with the messages
     }
+
+    err := result.Next(ctx)
+    if err != nil {
+        // Handle error ...
+    }
 }
 ```
 

waku/v2/protocol/store/client.go

@@ -215,8 +215,7 @@ func (s *WakuStore) next(ctx context.Context, r *Result) (*Result, error) {
 	if r.IsComplete() {
 		return &Result{
 			store:         s,
-			started:       true,
+			messages:      nil,
-			messages:      []*pb.WakuMessageKeyValue{},
 			cursor:        nil,
 			storeRequest:  r.storeRequest,
 			storeResponse: r.storeResponse,
@@ -234,7 +233,6 @@ func (s *WakuStore) next(ctx context.Context, r *Result) (*Result, error) {
 	}
 
 	result := &Result{
-		started:       true,
 		store:         s,
 		messages:      response.Messages,
 		storeRequest:  storeRequest,

waku/v2/protocol/store/client_test.go

@@ -78,7 +78,7 @@ func TestStoreClient(t *testing.T) {
 	startTime := utils.GetUnixEpoch(timesource.NewDefaultClock())
 	for i := 0; i < 5; i++ {
 		msg := &pb.WakuMessage{
-			Payload:      []byte{1, 2, 3, 4, 5},
+			Payload:      []byte{byte(i), 1, 2, 3, 4, 5},
 			ContentTopic: "test",
 			Version:      proto.Uint32(0),
 			Timestamp:    utils.GetUnixEpoch(timesource.NewDefaultClock()),
@@ -108,71 +108,71 @@ func TestStoreClient(t *testing.T) {
 	require.NoError(t, err)
 
 	// -- First page:
-	hasNext, err := response.Next(ctx)
-	require.NoError(t, err)
-	require.True(t, hasNext)
 	require.False(t, response.IsComplete())
 	require.Len(t, response.messages, 2)
 	require.Equal(t, response.messages[0].Message.GetTimestamp(), messages[0].GetTimestamp())
 	require.Equal(t, response.messages[1].Message.GetTimestamp(), messages[1].GetTimestamp())
 
-	// -- Second page:
+	err = response.Next(ctx)
-	hasNext, err = response.Next(ctx)
 	require.NoError(t, err)
-	require.True(t, hasNext)
+
+	// -- Second page:
 	require.False(t, response.IsComplete())
 	require.Len(t, response.messages, 2)
 	require.Equal(t, response.messages[0].Message.GetTimestamp(), messages[2].GetTimestamp())
 	require.Equal(t, response.messages[1].Message.GetTimestamp(), messages[3].GetTimestamp())
 
-	// -- Third page:
+	err = response.Next(ctx)
-	hasNext, err = response.Next(ctx)
 	require.NoError(t, err)
-	require.False(t, hasNext)
+
-	require.True(t, response.IsComplete())
+	// -- Third page:
+	require.False(t, response.IsComplete())
 	require.Len(t, response.messages, 1)
 	require.Equal(t, response.messages[0].Message.GetTimestamp(), messages[4].GetTimestamp())
 
-	// -- Trying to continue a completed cursor
+	err = response.Next(ctx)
-	hasNext, err = response.Next(ctx)
 	require.NoError(t, err)
-	require.False(t, hasNext)
+
+	// -- Trying to continue a completed cursor
 	require.True(t, response.IsComplete())
+	require.Len(t, response.messages, 0)
+
+	err = response.Next(ctx)
+	require.NoError(t, err)
 
 	// Query messages with backward pagination
 	response, err = wakuStore.Query(ctx, FilterCriteria{ContentFilter: protocol.NewContentFilter(relay.DefaultWakuTopic, "test"), TimeStart: startTime, TimeEnd: endTime}, WithPaging(false, 2))
 	require.NoError(t, err)
 
 	// -- First page:
-	hasNext, err = response.Next(ctx)
-	require.NoError(t, err)
-	require.True(t, hasNext)
 	require.False(t, response.IsComplete())
 	require.Len(t, response.messages, 2)
 	require.Equal(t, response.messages[0].Message.GetTimestamp(), messages[3].GetTimestamp())
 	require.Equal(t, response.messages[1].Message.GetTimestamp(), messages[4].GetTimestamp())
 
-	// -- Second page:
+	err = response.Next(ctx)
-	hasNext, err = response.Next(ctx)
 	require.NoError(t, err)
-	require.True(t, hasNext)
+
+	// -- Second page:
 	require.False(t, response.IsComplete())
 	require.Len(t, response.messages, 2)
 	require.Equal(t, response.messages[0].Message.GetTimestamp(), messages[1].GetTimestamp())
 	require.Equal(t, response.messages[1].Message.GetTimestamp(), messages[2].GetTimestamp())
 
-	// -- Third page:
+	err = response.Next(ctx)
-	hasNext, err = response.Next(ctx)
 	require.NoError(t, err)
-	require.False(t, hasNext)
+
-	require.True(t, response.IsComplete())
+	// -- Third page:
+	require.False(t, response.IsComplete())
 	require.Len(t, response.messages, 1)
 	require.Equal(t, response.messages[0].Message.GetTimestamp(), messages[0].GetTimestamp())
 
-	// -- Trying to continue a completed cursor
+	err = response.Next(ctx)
-	hasNext, err = response.Next(ctx)
+	require.NoError(t, err)
+
+	// -- Trying to continue a completed cursor
+	err = response.Next(ctx)
 	require.NoError(t, err)
-	require.False(t, hasNext)
 	require.True(t, response.IsComplete())
 
 	// No cursor should be returned if there are no messages that match the criteria

waku/v2/protocol/store/result.go

@@ -9,7 +9,9 @@ import (
 
 // Result represents a valid response from a store node
 type Result struct {
-	started       bool
+	noCursor bool
+	done     bool
+
 	messages      []*pb.WakuMessageKeyValue
 	store         *WakuStore
 	storeRequest  *pb.StoreQueryRequest
@@ -23,7 +25,7 @@ func (r *Result) Cursor() []byte {
 }
 
 func (r *Result) IsComplete() bool {
-	return r.cursor == nil
+	return r.noCursor && r.done
 }
 
 func (r *Result) PeerID() peer.ID {
@@ -38,30 +40,28 @@ func (r *Result) Response() *pb.StoreQueryResponse {
 	return r.storeResponse
 }
 
-func (r *Result) Next(ctx context.Context) (bool, error) {
+func (r *Result) Next(ctx context.Context) error {
-	if !r.started {
+	if r.noCursor {
-		r.started = true
+		r.done = true
-		return len(r.messages) != 0, nil
+		r.messages = nil
-	}
+		return nil
-
-	if r.IsComplete() {
-		return false, nil
 	}
 
 	newResult, err := r.store.next(ctx, r)
 	if err != nil {
-		return false, err
+		return err
 	}
 
 	r.cursor = newResult.cursor
 	r.messages = newResult.messages
 
-	return !r.IsComplete(), nil
+	if r.cursor == nil {
+		r.noCursor = true
+	}
+
+	return nil
 }
 
 func (r *Result) Messages() []*pb.WakuMessageKeyValue {
-	if !r.started {
-		return nil
-	}
 	return r.messages
 }