fix(bitswap/notifications) subscribe to many

License: MIT
Signed-off-by: Brian Tiger Chow <brian@perfmode.com>

exchange/bitswap/notifications/notifications.go

@@ -29,10 +29,7 @@ func (ps *impl) Publish(block *blocks.Block) {
 	ps.wrapped.Pub(block, topic)
 }
 
-// Subscribe returns a channel of blocks for the given |keys|. |blockChannel|
-// is closed if the |ctx| times out or is cancelled, or after sending len(keys)
-// blocks.
-func (ps *impl) Subscribe(ctx context.Context, keys ...u.Key) <-chan *blocks.Block {
+func (ps *impl) SubscribeDeprec(ctx context.Context, keys ...u.Key) <-chan *blocks.Block {
 	topics := make([]string, 0)
 	for _, key := range keys {
 		topics = append(topics, string(key))
@@ -57,3 +54,49 @@ func (ps *impl) Subscribe(ctx context.Context, keys ...u.Key) <-chan *blocks.Blo
 func (ps *impl) Shutdown() {
 	ps.wrapped.Shutdown()
 }
+
+// Subscribe returns a channel of blocks for the given |keys|. |blockChannel|
+// is closed if the |ctx| times out or is cancelled, or after sending len(keys)
+// blocks.
+func (ps *impl) Subscribe(ctx context.Context, keys ...u.Key) <-chan *blocks.Block {
+	topics := toStrings(keys)
+	blocksCh := make(chan *blocks.Block, len(keys))
+	valuesCh := make(chan interface{}, len(keys))
+	ps.wrapped.AddSub(valuesCh, topics...)
+
+	go func() {
+		defer func() {
+			ps.wrapped.Unsub(valuesCh, topics...)
+			close(blocksCh)
+		}()
+		for _, _ = range keys {
+			select {
+			case <-ctx.Done():
+				return
+			case val, ok := <-valuesCh:
+				if !ok {
+					return
+				}
+				block, ok := val.(*blocks.Block)
+				if !ok {
+					return
+				}
+				select {
+				case <-ctx.Done():
+					return
+				case blocksCh <- block: // continue
+				}
+			}
+		}
+	}()
+
+	return blocksCh
+}
+
+func toStrings(keys []u.Key) []string {
+	strs := make([]string, 0)
+	for _, key := range keys {
+		strs = append(strs, string(key))
+	}
+	return strs
+}