Go语言实现pow协议

package main

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/davecgh/go-spew/spew"
	"github.com/gorilla/mux"
	"github.com/joho/godotenv"

)

/*
	新建 .env ，添加 ADDR=9000
	新建 main.go，引入相应的包

	go run main.go 启动当前服务 控制台打印出如下消息

	2020/01/01 14:05:28 Listening on  9000
	(main.Block) {
	 Index: (int) 0,
	 Timestamp: (string) (len=51) "2020-01-01 14:05:28.320064 +0800 CST m=+0.000794081",
	 BPM: (int) 0,
	 Hash: (string) (len=64) "f1534392279bddbf9d43dde8701cb5be14b82f76ec6607bf8d6ad557f60f304e",
	 PrevHash: (string) "",
	 Difficulty: (int) 1,
	 Nonce: (string) ""
	}
	// 使用curl 请求生成新的区块
	curl -d '{"BMP": 20}' http://localhost:9000

	53a7710028d4aee15bcf06918508aa0107387a9432018089f6c507b8e1230045  do more work!
	d19f8f83b7e315126ba341ab1cc7d1d75acbbedde48e2a619fc70958a8f1cd16  do more work!
	c5d959b91b8d62a13ff4c153ea87b150a1fa2b7df17901b3bd67bae288296fe6  do more work!
	f21e06d0c3fd40d44dc9aac5b3acbbe768b9c223233da1ca63e1ffd1cf837b26  do more work!
	b1f09c6d3853af434001755f9c51f3477ff8fb42beafe836de4f21b3e5bd804b  do more work!
	ece1a6aa8d28f08806e5452bd4a418b8517525a0f96798d87e38f3015320da0c  do more work!
	fd18e42806c63e91fc674430e3e4c9d62662630823fff6844db16ce5abcf5d53  do more work!
	19e96095db4136996e4962e68002ee1cc053771c6496c389f6337e0abd3ba826  do more work!
	...
	// 查看当前已经生成的区块
	浏览器访问：http://localhost:9000

 */
// 代表难度系数，如果赋值为 1，则需要判断生成区块时所产生的 Hash 前缀至少包含1个 0
const difficulty = 1

/*

	Block 代表区块的结构体。

	Index 是区块链中数据记录的位置

	Timestamp 是自动确定的，并且是写入数据的时间

	BPM 是每分钟跳动的次数，是你的脉率

	Hash 是代表这个数据记录的SHA256标识符

	PrevHash 是链中上一条记录的SHA256标识符

	Difficulty 是当前区块的难度系数
	Nonce 是 PoW 挖矿中符合条件的数字
	Blockchain 是存放区块数据的集合
	Message 是使用 POST 请求传递的数据
	mutex 是为了防止同一时间产生多个区块
*/

//声明区块
type Block struct {
	Index      int
	Timestamp  string
	BPM        int
	Hash       string
	PrevHash   string
	Difficulty int
	Nonce      string
}

var Blockchain []Block

type Message struct {
	BPM int
}

var mutex = &sync.Mutex{}

//生成区块
func generateBlock(oldBlock Block, BPM int) Block {
	var newBlock Block

	t := time.Now()

	newBlock.Index = oldBlock.Index + 1
	newBlock.Timestamp = t.String()
	newBlock.BPM = BPM
	newBlock.PrevHash = oldBlock.Hash
	newBlock.Difficulty = difficulty

	for i := 0; ; i++ {
		hex := fmt.Sprintf("%x", i)
		newBlock.Nonce = hex
		if !isHashValid(calculateHash(newBlock), newBlock.Difficulty) {
			fmt.Println(calculateHash(newBlock), " do more work!")
			time.Sleep(time.Second)
			continue
		} else {
			fmt.Println(calculateHash(newBlock), " work done!")
			newBlock.Hash = calculateHash(newBlock)
			break
		}

	}
	return newBlock
}
//判断产生的哈希值是否合法
func isHashValid(hash string, difficulty int) bool {
	//复制 difficulty 个0，并返回新字符串，当 difficulty 为2 ，则 prefix 为 00
	prefix := strings.Repeat("0", difficulty)
	// HasPrefix判断字符串 hash 是否包含前缀 prefix
	return strings.HasPrefix(hash, prefix)
}
// 根据设定的规则，生成 Hash 值
func calculateHash(block Block) string {
	record := strconv.Itoa(block.Index) + block.Timestamp + strconv.Itoa(block.BPM) + block.PrevHash + block.Nonce
	h := sha256.New()
	h.Write([]byte(record))
	hashed := h.Sum(nil)
	return hex.EncodeToString(hashed)
}

// 验证区块
func isBlockValid(newBlock, oldBlock Block) bool {
	if oldBlock.Index+1 != newBlock.Index {
		return false
	}

	if oldBlock.Hash != newBlock.PrevHash {
		return false
	}

	if calculateHash(newBlock) != newBlock.Hash {
		return false
	}

	return true
}

// web服务器

func run() error {
	mux := makeMuxRouter()
	httpAddr := os.Getenv("ADDR")
	log.Println("Listening on ", os.Getenv("ADDR"))
	s := &http.Server{
		Addr:           ":" + httpAddr,
		Handler:        mux,
		ReadTimeout:    10 * time.Second,
		WriteTimeout:   10 * time.Second,
		MaxHeaderBytes: 1 << 20,
	}

	if err := s.ListenAndServe(); err != nil {
		return err
	}

	return nil
}

func makeMuxRouter() http.Handler {
	muxRouter := mux.NewRouter()
	muxRouter.HandleFunc("/", handleGetBlockchain).Methods("GET")
	muxRouter.HandleFunc("/", handleWriteBlock).Methods("POST")
	return muxRouter
}

// handleGetBlockchain 获取所有区块的列表信息

func handleGetBlockchain(w http.ResponseWriter, r *http.Request) {
	bytes, err := json.MarshalIndent(Blockchain, "", "  ")
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	io.WriteString(w, string(bytes))
}

// 生成新的区块
func handleWriteBlock(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	var m Message

	decoder := json.NewDecoder(r.Body)
	if err := decoder.Decode(&m); err != nil {
		respondWithJSON(w, r, http.StatusBadRequest, r.Body)
		return
	}
	defer r.Body.Close()

	//ensure atomicity when creating new block
	mutex.Lock()
	newBlock := generateBlock(Blockchain[len(Blockchain)-1], m.BPM)
	mutex.Unlock()

	if isBlockValid(newBlock, Blockchain[len(Blockchain)-1]) {
		Blockchain = append(Blockchain, newBlock)
		spew.Dump(Blockchain)
	}

	respondWithJSON(w, r, http.StatusCreated, newBlock)

}
// 返回json格式
func respondWithJSON(w http.ResponseWriter, r *http.Request, code int, payload interface{}) {
	w.Header().Set("Content-Type", "application/json")
	response, err := json.MarshalIndent(payload, "", "  ")
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte("HTTP 500: Internal Server Error"))
		return
	}
	w.WriteHeader(code)
	w.Write(response)
}

func main() {
	// 根目录的文件 .env 读取相应的变量
	err := godotenv.Load()
	if err != nil {
		log.Fatal(err)
	}

	go func() {
		t := time.Now()
		// 创建初始区块
		genesisBlock := Block{}
		genesisBlock = Block{0, t.String(), 0, calculateHash(genesisBlock), "", difficulty, ""}
		spew.Dump(genesisBlock)

		mutex.Lock()
		Blockchain = append(Blockchain, genesisBlock)
		mutex.Unlock()
	}()
	// 启动web服务
	log.Fatal(run())

}