// RequestBlocks get the blocks from the other PeerEndpoint based upon supplied SyncBlockRange, will provide them through the returned channel.
// this will also stop writing any received blocks to channels created from Prior calls to RequestBlocks(..)
func (d *Handler) RequestBlocks(syncBlockRange *pb.SyncBlockRange) (<-chan *pb.SyncBlocks, error) {
	d.syncBlocksRequestHandler.Lock()
	defer d.syncBlocksRequestHandler.Unlock()

	d.syncBlocksRequestHandler.reset()
	syncBlockRange.CorrelationId = d.syncBlocksRequestHandler.correlationID

	// Marshal the SyncBlockRange as the payload
	syncBlockRangeBytes, err := proto.Marshal(syncBlockRange)
	if err != nil {
		return nil, fmt.Errorf("Error marshaling syncBlockRange during GetBlocks: %s", err)
	}
	peerLogger.Debugf("Sending %s with Range %s", pb.Message_SYNC_GET_BLOCKS.String(), syncBlockRange)
	if err := d.SendMessage(&pb.Message{Type: pb.Message_SYNC_GET_BLOCKS, Payload: syncBlockRangeBytes}); err != nil {
		return nil, fmt.Errorf("Error sending %s during GetBlocks: %s", pb.Message_SYNC_GET_BLOCKS, err)
	}
	return d.syncBlocksRequestHandler.channel, nil
}

// RequestStateDeltas get the state snapshot deltas from the other PeerEndpoint, will provide them through the returned channel.
// this will also stop writing any received syncStateSnapshot(s) to channels created from Prior calls to GetStateSnapshot()
func (d *Handler) RequestStateDeltas(syncBlockRange *pb.SyncBlockRange) (<-chan *pb.SyncStateDeltas, error) {
	d.syncStateDeltasRequestHandler.Lock()
	defer d.syncStateDeltasRequestHandler.Unlock()
	// Reset the handler
	d.syncStateDeltasRequestHandler.reset()
	syncBlockRange.CorrelationId = d.syncStateDeltasRequestHandler.correlationID

	// Create the syncStateSnapshotRequest
	syncStateDeltasRequest := d.syncStateDeltasRequestHandler.createRequest(syncBlockRange)
	syncStateDeltasRequestBytes, err := proto.Marshal(syncStateDeltasRequest)
	if err != nil {
		return nil, fmt.Errorf("Error marshaling syncStateDeltasRequest during RequestStateDeltas: %s", err)
	}
	peerLogger.Debugf("Sending %s with syncStateDeltasRequest = %s", pb.Message_SYNC_STATE_GET_DELTAS.String(), syncStateDeltasRequest)
	if err := d.SendMessage(&pb.Message{Type: pb.Message_SYNC_STATE_GET_DELTAS, Payload: syncStateDeltasRequestBytes}); err != nil {
		return nil, fmt.Errorf("Error sending %s during RequestStateDeltas: %s", pb.Message_SYNC_STATE_GET_DELTAS, err)
	}

	return d.syncStateDeltasRequestHandler.channel, nil
}