From 942120679bd8fd845df826314c592cb508396edf Mon Sep 17 00:00:00 2001
From: Ivan Kuznetsov <me@jeiwan.ru>
Date: Sun, 10 Sep 2017 12:02:46 +0700
Subject: [PATCH] Clean up block.go; rework transaction hashing

---
 block.go       | 30 +++++++++++++++---------------
 transaction.go | 26 ++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/block.go b/block.go
index 3baaa46..b98c79c 100644
--- a/block.go
+++ b/block.go
@@ -8,7 +8,7 @@ import (
 	"time"
 )
 
-// Block keeps block headers
+// Block represents a block in the blockchain
 type Block struct {
 	Timestamp     int64
 	Transactions  []*Transaction
@@ -34,26 +34,13 @@ func NewGenesisBlock(coinbase *Transaction) *Block {
 	return NewBlock([]*Transaction{coinbase}, []byte{})
 }
 
-// DeserializeBlock deserializes a block
-func DeserializeBlock(d []byte) *Block {
-	var block Block
-
-	decoder := gob.NewDecoder(bytes.NewReader(d))
-	err := decoder.Decode(&block)
-	if err != nil {
-		log.Panic(err)
-	}
-
-	return &block
-}
-
 // HashTransactions returns a hash of the transactions in the block
 func (b *Block) HashTransactions() []byte {
 	var txHashes [][]byte
 	var txHash [32]byte
 
 	for _, tx := range b.Transactions {
-		txHashes = append(txHashes, tx.ID)
+		txHashes = append(txHashes, tx.Hash())
 	}
 	txHash = sha256.Sum256(bytes.Join(txHashes, []byte{}))
 
@@ -72,3 +59,16 @@ func (b *Block) Serialize() []byte {
 
 	return result.Bytes()
 }
+
+// DeserializeBlock deserializes a block
+func DeserializeBlock(d []byte) *Block {
+	var block Block
+
+	decoder := gob.NewDecoder(bytes.NewReader(d))
+	err := decoder.Decode(&block)
+	if err != nil {
+		log.Panic(err)
+	}
+
+	return &block
+}
diff --git a/transaction.go b/transaction.go
index e5176d6..99e4282 100644
--- a/transaction.go
+++ b/transaction.go
@@ -29,7 +29,33 @@ func (tx Transaction) IsCoinbase() bool {
 	return len(tx.Vin) == 1 && len(tx.Vin[0].Txid) == 0 && tx.Vin[0].Vout == -1
 }
 
+// Serialize returns a serialized Transaction
+func (tx Transaction) Serialize() []byte {
+	var encoded bytes.Buffer
+
+	enc := gob.NewEncoder(&encoded)
+	err := enc.Encode(tx)
+	if err != nil {
+		log.Panic(err)
+	}
+
+	return encoded.Bytes()
+}
+
+// Hash returns the hash of the Transaction
+func (tx *Transaction) Hash() []byte {
+	var hash [32]byte
+
+	txCopy := *tx
+	txCopy.ID = []byte{}
+
+	hash = sha256.Sum256(txCopy.Serialize())
+
+	return hash[:]
+}
+
 // SetID sets ID of a transaction
+// TODO: Remove this
 func (tx *Transaction) SetID() {
 	var encoded bytes.Buffer
 	var hash [32]byte