From 3d5c33ee1485be6d5554c4f31c63f78453e26b4d Mon Sep 17 00:00:00 2001
From: Minh Doan <daywednes@gmail.com>
Date: Mon, 11 Jun 2018 00:07:32 -0700
Subject: [PATCH] add CreateBlockchain

---
 block.go       | 44 +++++++++++++++++-----------------
 blockchain.go  | 14 +++++++++++
 transaction.go | 65 ++++++++++++++++++++++++++++++++++++++++++++++----
 3 files changed, 97 insertions(+), 26 deletions(-)

diff --git a/block.go b/block.go
index c330db6ad..bf99487b1 100644
--- a/block.go
+++ b/block.go
@@ -16,6 +16,28 @@ type Block struct {
 	Hash          []byte
 }
 
+// Serialize serializes the block
+func (b *Block) Serialize() []byte {
+	var result bytes.Buffer
+	encoder := gob.NewEncoder(&result)
+	err := encoder.Encode(b)
+	if err != nil {
+		log.Panic(err)
+	}
+	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
+}
+
 // HashTransactions returns a hash of the transactions in the block
 func (b *Block) HashTransactions() []byte {
 	var txHashes [][]byte
@@ -28,17 +50,6 @@ func (b *Block) HashTransactions() []byte {
 	return txHash[:]
 }
 
-// Serialize serializes the block
-func (b *Block) Serialize() []byte {
-	var result bytes.Buffer
-	encoder := gob.NewEncoder(&result)
-	err := encoder.Encode(b)
-	if err != nil {
-		log.Panic(err)
-	}
-	return result.Bytes()
-}
-
 // NewBlock creates and returns Block.
 func NewBlock(transactions []*Transaction, prevBlockHash []byte) *Block {
 	block := &Block{time.Now().Unix(), transactions, prevBlockHash, []byte{}, 0}
@@ -50,14 +61,3 @@ func NewBlock(transactions []*Transaction, prevBlockHash []byte) *Block {
 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
-}
diff --git a/blockchain.go b/blockchain.go
index c3d5e128c..7365bc6d0 100644
--- a/blockchain.go
+++ b/blockchain.go
@@ -9,6 +9,8 @@ type Blockchain struct {
 	blocks []*Block
 }
 
+const genesisCoinbaseData = "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks"
+
 // NewBlockchain creates a new Blockchain with genesis Block
 func NewBlockchain(address string) *Blockchain {
 	return &Blockchain{[]*Block{NewGenesisBlock()}}
@@ -87,3 +89,15 @@ Work:
 
 	return accumulated, unspentOutputs
 }
+
+// CreateBlockchain creates a new blockchain DB
+func CreateBlockchain(address string) *Blockchain {
+	// TODO: We assume we have not created any blockchain before.
+	// In current bitcoin, we can check if we created a blockchain before accessing local db.
+	cbtx := NewCoinbaseTX(address, genesisCoinbaseData)
+	genesis := NewGenesisBlock(cbtx)
+
+	bc := Blockchain{[]*Block{genesis}}
+
+	return &bc
+}
diff --git a/transaction.go b/transaction.go
index f37fdc7f4..51480aad3 100644
--- a/transaction.go
+++ b/transaction.go
@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"crypto/sha256"
 	"encoding/gob"
+	"encoding/hex"
+	"fmt"
 	"log"
 )
 
@@ -14,19 +16,24 @@ type Transaction struct {
 	txOutput []TXOutput
 }
 
+// TXOutput is the struct of transaction output in a transaction.
 type TXOutput struct {
-	address string
 	value   int
+	address string
 }
 
+// TXInput is the struct of transaction input in a transaction.
 type TXInput struct {
-	txId          []byte
+	txID          []byte
 	txOutputIndex int
 	address       string
 }
 
+// defaultCoinbaseValue is the default value of coinbase transaction.
+const defaultCoinbaseValue = 10
+
 // SetID sets ID of a transaction
-func (tx *Transaction) SetId() {
+func (tx *Transaction) SetID() {
 	var encoded bytes.Buffer
 	var hash [32]byte
 
@@ -36,5 +43,55 @@ func (tx *Transaction) SetId() {
 		log.Panic(err)
 	}
 	hash = sha256.Sum256(encoded.Bytes())
-	tx.ID = hash[:]
+	tx.id = hash[:]
+}
+
+// NewCoinbaseTX creates a new coinbase transaction
+func NewCoinbaseTX(to, data string) *Transaction {
+	if data == "" {
+		data = fmt.Sprintf("Reward to '%s'", to)
+	}
+
+	txin := TXInput{[]byte{}, -1, data}
+	txout := TXOutput{defaultCoinbaseValue, to}
+	tx := Transaction{nil, []TXInput{txin}, []TXOutput{txout}}
+	tx.SetID()
+
+	return &tx
+}
+
+// NewUTXOTransaction creates a new transaction
+func NewUTXOTransaction(from, to string, amount int, bc *Blockchain) *Transaction {
+	var inputs []TXInput
+	var outputs []TXOutput
+
+	acc, validOutputs := bc.FindSpendableOutputs(from, amount)
+
+	if acc < amount {
+		log.Panic("ERROR: Not enough funds")
+	}
+
+	// Build a list of inputs
+	for txid, outs := range validOutputs {
+		txID, err := hex.DecodeString(txid)
+		if err != nil {
+			log.Panic(err)
+		}
+
+		for _, out := range outs {
+			input := TXInput{txID, out, from}
+			inputs = append(inputs, input)
+		}
+	}
+
+	// Build a list of outputs
+	outputs = append(outputs, TXOutput{amount, to})
+	if acc > amount {
+		outputs = append(outputs, TXOutput{acc - amount, from}) // a change
+	}
+
+	tx := Transaction{nil, inputs, outputs}
+	tx.SetID()
+
+	return &tx
 }