BlockChain.go

package main

import (
	"log"
	"github.com/boltdb/bolt"
	"os"
	"fmt"
	"encoding/hex"
)

const dbFile = "blockchain_%s.db"
const blocksBucket = "blocks"
const genesisCoinbaseData = "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks"

/*
Base type to to contains block
*/
type BlockChain struct {
	tip []byte //hash of last block in a chain
	db  *bolt.DB
}

/*
Find all unspent transaction for appropriate address
*/
func (bc *BlockChain) FindUnspentTransactions(address string) []Transaction  {
	var unspentTXs []Transaction
	spentTXOs := make(map[string][]int)
	bci := bc.Iterator()

	for {
		block := bci.Next()

		// Loop through all transactions
		for _, tx := range block.Transactions {
			txID := hex.EncodeToString(tx.ID)

		Outputs:
			for outIdx, out := range tx.Vout {

				//Was the output spent ?
				if spentTXOs[txID] != nil {
					for _, spentOut := range spentTXOs[txID] {
						if spentOut == outIdx {
							continue Outputs
						}
					}
				}

				if out.CanBeUnlockedWith(address) {
					unspentTXs = append(unspentTXs, *tx)
				}
			}

			if tx.IsCoinbase() == false {
				for _, in := range tx.Vin {
					if in.CanUnlockOutputWith(address) {
						inTxID := hex.EncodeToString(in.Txid)
						spentTXOs[inTxID] = append(spentTXOs[inTxID], in.Vout)
					}
				}
			}
		}

		if len(block.PrevBlockHash) == 0 {
			break
		}
	}

	return unspentTXs
}

/*

*/
func (bc *BlockChain) FindSpendableOutputs(address string, amount int) (int, map[string][]int) {
	unspentOutputs := make(map[string][]int)
	unspentTXs := bc.FindUnspentTransactions(address)
	accumulated := 0
Work:
	for _, tx := range unspentTXs {
		txID := hex.EncodeToString(tx.ID)

		for outIdx, out := range tx.Vout {
			if out.CanBeUnlockedWith(address) && accumulated < amount {
				accumulated += out.Value
				unspentOutputs[txID] = append(unspentOutputs[txID], outIdx)
			}

			if accumulated >= amount {
				break Work
			}
		}
	}

	return accumulated, unspentOutputs
}

/*
Find all unspent outputs for appropriate address
*/
func (bc *BlockChain) FindUTXO(address string) []TXOutput {
	var UTXOs []TXOutput

	unspentTransactions := bc.FindUnspentTransactions(address)

	for _, tx := range unspentTransactions {
		for _, out := range  tx.Vout {
			if out.CanBeUnlockedWith(address) {
				UTXOs = append(UTXOs, out)
			}
		}
	}
	return UTXOs
}


func (bc *BlockChain) MineBlock(transactions []*Transaction) {
	var lastHash []byte

	err := bc.db.View(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte(blocksBucket))
		lastHash = b.Get([]byte("l"))

		return nil
	})

	if err != nil {
		log.Panic(err)
	}

	newBlock := NewBlock(transactions, lastHash)

	err = bc.db.Update(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte(blocksBucket))
		err := b.Put(newBlock.Hash, newBlock.Serialize())
		if err != nil {
			log.Panic(err)
		}

		err = b.Put([]byte("l"), newBlock.Hash)
		if err != nil {
			log.Panic(err)
		}

		bc.tip = newBlock.Hash

		return nil
	})
}

/*
Creates a new BlockChain DB
*/
func CreateBlockChain(address, nodeID string) *BlockChain {

	dbFile := fmt.Sprintf(dbFile, nodeID)
	if dbExists(dbFile) {
		fmt.Println("Blockchain already exists.")
		os.Exit(1)
	}


	db, err := bolt.Open(dbFile, 0600, nil)
	if err != nil {
		log.Fatal(err)
	}

	cbtx := NewCoinbaseTX(address, genesisCoinbaseData)
	genesis := NewGenesisBlock(cbtx)

	var tip []byte
	err = db.Update(func(tx *bolt.Tx) error {

		b, err := tx.CreateBucket([]byte(blocksBucket))
		if err != nil {
			log.Fatal(err)
		}

		err = b.Put(genesis.Hash, genesis.Serialize())
		if err != nil {
			log.Fatal(err)
		}

		err = b.Put([]byte("l"), genesis.Hash)
		if err != nil {
			log.Panic(err)
		}

		tip = genesis.Hash

		return nil
	})

	if err != nil {
		log.Fatal(err)
	}

	bc := BlockChain{tip, db}

	return &bc
}

/*
Create BlockChain with Genesis-Blocks
*/
func NewBlockChain(nodeID string) *BlockChain {

	dbFile := fmt.Sprintf(dbFile, nodeID)
	if dbExists(dbFile) == false {
		fmt.Println("No existing blockchain found. Create one first.")
		os.Exit(1)
	}

	var tip []byte
	db, err := bolt.Open(dbFile, 0600, nil)
	if err != nil {
		log.Fatal(err)
	}

	err = db.Update(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte(blocksBucket))
		tip = b.Get([]byte("l"))

		return nil
	})

	if err != nil {
		log.Panic(err)
	}

	bc := BlockChain{tip, db}

	return &bc
}

func dbExists(dbFile string) bool {
	if _, err := os.Stat(dbFile); os.IsNotExist(err) {
		return false
	}

	return true
}