package main

import (
	"bytes"
	"crypto/sha256"
	"time"
)

// Block keeps block headers.
type Block struct {
	Timestamp     int64
	Transactions  []*Transaction
	PrevBlockHash []byte
	Hash          []byte
}

// 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)
	}
	txHash = sha256.Sum256(bytes.Join(txHashes, []byte{}))
	return txHash[:]
}

// NewBlock creates and returns Block.
func NewBlock(utxoPool []UTXOPool, prevBlockHash []byte) *Block {

	block := &Block{time.Now().Unix(), utxoPool, prevBlockHash, []byte{}}
	block.SetHash()
	return block
}

// NewGenesisBlock creates and returns genesis Block.
func NewGenesisBlock() *Block {
	genesisUTXOPool := UTXOPool{}
	genesisUTXOPool.utxos["genesis"] = TOTAL_COINS

	return NewBlock(genesisUTXOPool, []byte{})
}