Simple Block Chain Mechanism in Go for Learning Purpose

block.go

package main

import (
	"crypto/sha256"
	"encoding/json"
	"fmt"
	"strings"
)

// Data ...
type Data struct {
	amount int
	msg    string
}

// Block ...
type Block struct {
	nonce        int
	hash         string
	index        int
	ts           string
	data         Data
	previousHash string
}

// CreateBlock ...
func CreateBlock(index int, ts string, data Data) *Block {
	block := new(Block)
	block.index = index
	block.data = data
	block.ts = ts
	block.nonce = 0
	block.previousHash = ""
	calculateHash(block)
	return block
}

// Mine ...
func Mine(difficulty int, block *Block) bool {
	zeros := make([]int, difficulty, difficulty)                                            // create an array of zeros for difficulty
	zerosStr := strings.Trim(strings.Join(strings.Split(fmt.Sprint(zeros), " "), ""), "[]") // convert it to string
	for !strings.HasPrefix(block.hash, zerosStr) {
		block.nonce++
		fmt.Printf("\u2717: \x1b[31m%s\x1b[0m\n", block.hash)
		calculateHash(block)
	}
	fmt.Printf("\u2713: \x1b[32m%s\x1b[0m\n", block.hash)
	return true
}

func calculateHash(block *Block) {
	h := sha256.New()
	out, err := json.Marshal(fmt.Sprintf("%s", block))
	if err != nil {
		panic(err)
	}
	h.Write([]byte(string(out)))
	block.hash = fmt.Sprintf("%x", h.Sum(nil))
}

chain.go

package main

import (
	"fmt"
	"time"
)

// BlockChain ...
type BlockChain struct {
	difficulty int
	blocks     []*Block
}

// CreateChain ...
func (chain *BlockChain) CreateChain() *BlockChain {
	chain.difficulty = 4
	block1 := CreateBlock(0, time.Now().String(), Data{0, "0"})
	chain.blocks = append(chain.blocks, block1)
	return chain
}

// AddBlock ...
func (chain *BlockChain) AddBlock(block *Block) {
	block.previousHash = getLatestBlock(chain).hash
	Mine(chain.difficulty, block)
	chain.blocks = append(chain.blocks, block)
}

// Add ...
func (chain *BlockChain) Add(blocks []Block) {
	for i := range blocks {
		block := blocks[i]
		block.previousHash = getLatestBlock(chain).hash
		Mine(chain.difficulty, &block)
		if !chain.isChainValid() {
			chain.blocks = chain.blocks[:len(chain.blocks)-1] // remove it
		} else {
			chain.blocks = append(chain.blocks, &block)
		}
	}
}

// Print ...
func (chain BlockChain) Print() {
	for _, b := range chain.blocks {
		fmt.Printf("%+v\n", b)
	}
}
func getLatestBlock(chain *BlockChain) *Block {
	return chain.blocks[len(chain.blocks)-1]
}

func (chain *BlockChain) isChainValid() bool {
	for i := 1; i <= len(chain.blocks)-1; i++ {
		currentBlock := chain.blocks[i]
		previousBlock := chain.blocks[i-1]
		if currentBlock.previousHash != previousBlock.hash {
			return false
		}
	}
	return true
}

main.go

package main

import (
	"fmt"
	"time"
)

func main() {
	data1 := Data{1, "12133"}
	block1 := CreateBlock(1, time.Now().String(), data1)
	data2 := Data{1, "1223"}
	block2 := CreateBlock(2, time.Now().String(), data2)
	data3 := Data{1, "1123"}
	block3 := CreateBlock(3, time.Now().String(), data3)
	chain := new(BlockChain)
	chain.CreateChain()
	chain.AddBlock(block1)
	chain.AddBlock(block2)
	chain.AddBlock(block3)
	chain.Print()
	fmt.Println(chain.isChainValid())
}