package main

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

// Block keeps block headers
type Block struct {
	Timestamp int64
	Data      []byte
	PrevBlock []byte
	Hash      []byte
}

// SetHash calculates and sets block hash
func (b *Block) SetHash() {
	timestamp := []byte(strconv.FormatInt(b.Timestamp, 10))
	headers := bytes.Join([][]byte{b.PrevBlock, b.Data, timestamp}, []byte{})
	fmt.Printf("%s\n", headers)
	hash := sha256.Sum256(headers)

	b.Hash = hash[:]
}

// NewBlock creates and returns Block
func NewBlock(data string, prevBlock []byte) *Block {
	block := &Block{time.Now().Unix(), []byte(data), prevBlock, []byte("")}
	block.SetHash()
	return block
}

// NewGenesisBlock creates and returns genesis Block
func NewGenesisBlock() *Block {
	return NewBlock("Genesis Block", []byte("0"))
}