From 47bab858947054fc35fa26393a6173032b90db0f Mon Sep 17 00:00:00 2001
From: chao <chao@harmony.one>
Date: Tue, 6 Aug 2019 17:33:02 -0700
Subject: [PATCH] add message type and message handler placeholder for cross
 shard transactions

---
 api/proto/node/node.go   |  4 +++-
 node/node_cross_shard.go | 31 +++++++++++++++++++++++++++++++
 node/node_handler.go     | 17 ++++++++++++++++-
 3 files changed, 50 insertions(+), 2 deletions(-)
 create mode 100644 node/node_cross_shard.go

diff --git a/api/proto/node/node.go b/api/proto/node/node.go
index 3ee002b6c..756842f24 100644
--- a/api/proto/node/node.go
+++ b/api/proto/node/node.go
@@ -27,7 +27,6 @@ const (
 	PING // node send ip/pki to register with leader
 	PONG // node broadcast pubK
 	ShardState
-	// TODO: add more types
 )
 
 // BlockchainSyncMessage is a struct for blockchain sync message.
@@ -96,6 +95,9 @@ type BlockMessageType int
 // Block sync message subtype
 const (
 	Sync BlockMessageType = iota
+
+	Header  // used for crosslink from beacon chain to shard chain
+	Receipt // cross-shard transaction receipts
 )
 
 // SerializeBlockchainSyncMessage serializes BlockchainSyncMessage.
diff --git a/node/node_cross_shard.go b/node/node_cross_shard.go
new file mode 100644
index 000000000..364af0ebd
--- /dev/null
+++ b/node/node_cross_shard.go
@@ -0,0 +1,31 @@
+package node
+
+import (
+	"github.com/ethereum/go-ethereum/rlp"
+
+	"github.com/harmony-one/harmony/core/types"
+	"github.com/harmony-one/harmony/internal/utils"
+)
+
+// ProcessHeaderMessage verify and process Node/Header message into crosslink when it's valid
+func (node *Node) ProcessHeaderMessage(msgPayload []byte) {
+	var headers []*types.Header
+	err := rlp.DecodeBytes(msgPayload, &headers)
+	if err != nil {
+		utils.Logger().Error().
+			Err(err).
+			Msg("Crosslink Headers Broadcast Unable to Decode")
+		return
+	}
+	// TODO: add actual logic
+}
+
+// ProcessReceiptMessage store the receipts and merkle proof in local data store
+func (node *Node) ProcessReceiptMessage(msgPayload []byte) {
+	// TODO: add logic
+}
+
+// ProcessCrossShardTx verify and process cross shard transaction on destination shard
+func (node *Node) ProcessCrossShardTx(blocks []*types.Block) {
+	// TODO: add logic
+}
diff --git a/node/node_handler.go b/node/node_handler.go
index d2113f7aa..c47546d34 100644
--- a/node/node_handler.go
+++ b/node/node_handler.go
@@ -171,11 +171,13 @@ func (node *Node) messageHandler(content []byte, sender libp2p_peer.ID) {
 				} else {
 					// for non-beaconchain node, subscribe to beacon block broadcast
 					role := node.NodeConfig.Role()
-					if proto_node.BlockMessageType(msgPayload[0]) == proto_node.Sync && role == nodeconfig.Validator {
+					if role == nodeconfig.Validator {
 						utils.Logger().Info().
 							Uint64("block", blocks[0].NumberU64()).
 							Msg("Block being handled by block channel")
 
+						go node.ProcessCrossShardTx(blocks)
+
 						for _, block := range blocks {
 							node.BeaconBlockChannel <- block
 						}
@@ -185,6 +187,19 @@ func (node *Node) messageHandler(content []byte, sender libp2p_peer.ID) {
 						node.Client.UpdateBlocks(blocks)
 					}
 				}
+
+			case proto_node.Header:
+				// only beacon chain will accept the header from other shards
+				if node.Consensus.ShardID != 0 {
+					return
+				}
+				utils.Logger().Debug().Msg("NET: received message: Node/Header")
+				node.ProcessHeaderMessage(msgPayload[1:]) // skip first byte which is blockMsgType
+
+			case proto_node.Receipt:
+				utils.Logger().Debug().Msg("NET: received message: Node/Receipt")
+				node.ProcessReceiptMessage(msgPayload[1:]) // skip first byte which is blockMsgType
+
 			}
 		case proto_node.PING:
 			node.pingMessageHandler(msgPayload, sender)