naive chain written in golang.

naive_test.sh

#!/bin/bash

curl -v "http://localhost:8080/"
curl -v --data-urlencode "value=1" "http://localhost:10888" 
curl -v --data-urlencode "value=2" "http://localhost:10888" 
curl -v --data-urlencode "value=3" "http://localhost:10888" 
curl -v --data-urlencode "value=4" "http://localhost:10888" 
curl -v --data-urlencode "value=5" "http://localhost:10888" 

curl -v "http://localhost:8080/"

naivechain.go

package main

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"io"
	"log"
	"net/http"
	"time"

	"github.com/gorilla/mux"
)

type Block struct {
	Index     int
	Timestamp string
	Payload   []byte
	Hash      string
	PreHash   string
}

func calcHash(block Block) string {
	record := string(block.Index) + block.Timestamp + string(block.Payload)
	h := sha256.New()
	h.Write([]byte(record))
	hashed := h.Sum(nil)
	return hex.EncodeToString(hashed)
}

func genBlock(preBlock Block, payload []byte) (Block, error) {
	var newBlock Block
	t := time.Now()
	newBlock.Index = preBlock.Index + 1
	newBlock.Timestamp = t.String()
	newBlock.Payload = payload
	newBlock.PreHash = preBlock.Hash
	newBlock.Hash = calcHash(newBlock)
	return newBlock, nil
}

func isBlockValid(preBlock, block Block) bool {
	if preBlock.Index+1 != block.Index {
		return false
	}
	if block.PreHash != preBlock.Hash {
		return false
	}
	if calcHash(block) != block.Hash {
		return false
	}
	return true
}

var BlockChain []Block

func replaceChain(newBlocks []Block) {
	if len(newBlocks) > len(BlockChain) {
		BlockChain = newBlocks
	}
}

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

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

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

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))
}

func handleWriteBlock(w http.ResponseWriter, r *http.Request) {
	r.ParseForm()
	payload := r.Form.Get("value")
	newBlock, err := genBlock(BlockChain[len(BlockChain)-1], []byte(payload))
	if err != nil {
		respondWithJSON(w, r, http.StatusInternalServerError, err)
		return
	}
	if isBlockValid(BlockChain[len(BlockChain)-1], newBlock) {
		newBlockchain := append(BlockChain, newBlock)
		replaceChain(newBlockchain)
	}
	respondWithJSON(w, r, http.StatusCreated, newBlock)
}

func respondWithJSON(w http.ResponseWriter, r *http.Request, code int, payload interface{}) {
	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() {
	BlockChain = append(BlockChain, Block{0, time.Now().String(), []byte{}, "", ""})
	log.Fatal(run(":1080"))
}