From 9adb5fc1393c2d2ab0f4662cbff0fcffa296d87f Mon Sep 17 00:00:00 2001
From: Ivan Kuznetsov <me@jeiwan.ru>
Date: Sun, 1 Oct 2017 11:19:43 +0700
Subject: [PATCH] Implement 'getblocks' command

---
 blockchain.go | 18 +++++++++++++++
 server.go     | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 82 insertions(+)

diff --git a/blockchain.go b/blockchain.go
index 8d1cab7..0f310af 100644
--- a/blockchain.go
+++ b/blockchain.go
@@ -169,6 +169,24 @@ func (bc *Blockchain) Iterator() *BlockchainIterator {
 	return bci
 }
 
+// GetBlockHashes returns a list of hashes of all the blocks in the chain
+func (bc *Blockchain) GetBlockHashes() [][]byte {
+	var blocks [][]byte
+	bci := bc.Iterator()
+
+	for {
+		block := bci.Next()
+
+		blocks = append(blocks, block.Hash)
+
+		if len(block.PrevBlockHash) == 0 {
+			break
+		}
+	}
+
+	return blocks
+}
+
 // MineBlock mines a new block with the provided transactions
 func (bc *Blockchain) MineBlock(transactions []*Transaction) *Block {
 	var lastHash []byte
diff --git a/server.go b/server.go
index 37a87ac..0cbf599 100644
--- a/server.go
+++ b/server.go
@@ -22,6 +22,15 @@ type addr struct {
 	AddrList []string
 }
 
+type getblocks struct {
+	AddrFrom string
+}
+
+type inv struct {
+	Type  string
+	Items [][]byte
+}
+
 type verack struct {
 }
 
@@ -57,6 +66,12 @@ func extractCommand(request []byte) []byte {
 	return request[:commandLength]
 }
 
+func requestBlocks() {
+	for _, node := range knownNodes {
+		sendGetBlocks(node)
+	}
+}
+
 func sendAddr(address string) {
 	nodes := addr{knownNodes}
 	nodes.AddrList = append(nodes.AddrList, nodeAddress)
@@ -79,6 +94,21 @@ func sendData(addr string, data []byte) {
 	}
 }
 
+func sendInv(address, kind string, items [][]byte) {
+	inventory := inv{kind, items}
+	payload := gobEncode(inventory)
+	request := append(commandToBytes("inv"), payload...)
+
+	sendData(address, request)
+}
+
+func sendGetBlocks(address string) {
+	payload := gobEncode(getblocks{nodeAddress})
+	request := append(commandToBytes("getblocks"), payload...)
+
+	sendData(address, request)
+}
+
 func sendVersion(addr string) {
 	payload := gobEncode(verzion{nodeVersion, nodeAddress})
 
@@ -108,6 +138,36 @@ func handleAddr(request []byte) {
 
 	knownNodes = append(knownNodes, payload.AddrList...)
 	fmt.Printf("There are %d known nodes now!\n", len(knownNodes))
+	requestBlocks()
+}
+
+func handleInv(request []byte) {
+	var buff bytes.Buffer
+	var payload inv
+
+	buff.Write(request[commandLength:])
+	dec := gob.NewDecoder(&buff)
+	err := dec.Decode(&payload)
+	if err != nil {
+		log.Panic(err)
+	}
+
+	fmt.Printf("Recevied %d %s\n", len(payload.Items), payload.Type)
+}
+
+func handleGetBlocks(request []byte, bc *Blockchain) {
+	var buff bytes.Buffer
+	var payload getblocks
+
+	buff.Write(request[commandLength:])
+	dec := gob.NewDecoder(&buff)
+	err := dec.Decode(&payload)
+	if err != nil {
+		log.Panic(err)
+	}
+
+	blocks := bc.GetBlockHashes()
+	sendInv(payload.AddrFrom, "blocks", blocks)
 }
 
 func handleVersion(request []byte) {
@@ -137,6 +197,10 @@ func handleConnection(conn net.Conn, bc *Blockchain) {
 	switch command {
 	case "addr":
 		handleAddr(request)
+	case "inv":
+		handleInv(request)
+	case "getblocks":
+		handleGetBlocks(request, bc)
 	case "version":
 		handleVersion(request)
 	case "verack":