first commit

peer/blockchainlib/block.go

@@ -0,0 +1,20 @@
+package blockchainlib
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/json"
+	"log"
+)
+
+func HashBlock(b Block) string {
+	blockJson, err := json.Marshal(b)
+	if err != nil {
+		log.Println(err)
+	}
+	blockString := string(blockJson)
+
+	h := sha256.New()
+	h.Write([]byte(blockString))
+	return base64.URLEncoding.EncodeToString(h.Sum(nil))
+}

peer/blockchainlib/blockchain.go

@@ -0,0 +1,155 @@
+package blockchainlib
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"time"
+
+	"github.com/fatih/color"
+)
+
+type Block struct {
+	Hash         string    `json:"hash"`
+	Height       int64     `json:"height"`
+	Date         time.Time `json:"date"`
+	PreviousHash string    `json:"previoushash"`
+	NextHash     string    `json:"nexthash"`
+	Data         []string  `json:"data"`
+	Emitter      string    `json:"emitter"` //the ID of the peer that has emmited the block
+}
+
+type Blockchain struct {
+	GenesisBlock string    `json:"genesisblock"`
+	LastUpdate   time.Time `json:"lastupdate"`
+	Blocks       []Block   `json:"blocks"`
+}
+
+//var blockchain Blockchain
+
+func (bc *Blockchain) GetBlockByHash(hash string) (Block, error) {
+	for _, block := range bc.Blocks {
+		if block.Hash == hash {
+			return block, nil
+		}
+	}
+	var b Block
+	return b, errors.New("Block Hash not found")
+}
+
+func (bc *Blockchain) CreateBlock(data string) Block {
+	var b Block
+	b.Height = int64(len(bc.Blocks))
+	if len(bc.Blocks) == 0 {
+		b.Height = 0
+	} else {
+		b.PreviousHash = bc.Blocks[len(bc.Blocks)-1].Hash
+	}
+	b.Date = time.Now()
+	b.Data = append(b.Data, data)
+	//b.Emitter = runningPeer.ID
+
+	b.Hash = HashBlock(b)
+	return b
+}
+
+func (bc *Blockchain) BlockExists(block Block) bool {
+	for _, b := range bc.Blocks {
+		if b.Hash == block.Hash {
+			return true
+		}
+	}
+	return false
+}
+
+func (bc *Blockchain) AddBlock(block Block) error {
+	if bc.BlockExists(block) {
+		return errors.New("[Error adding Block]: Block already exists in the Blockchain")
+	}
+	if len(bc.Blocks) > 0 {
+		bc.Blocks[len(bc.Blocks)-1].NextHash = block.Hash
+	} else {
+		bc.GenesisBlock = block.Hash
+	}
+	bc.Blocks = append(bc.Blocks, block)
+
+	bc.SaveToDisk()
+
+	return nil
+}
+
+func (bc *Blockchain) ReconstructBlockchainFromBlock(urlAPI string, h string) {
+	color.Yellow("reconstructing the blockchain from last block in memory")
+	var block Block
+	var err error
+
+	block, err = bc.GetBlockByHash(h)
+	check(err)
+
+	if h == "" {
+		//no genesis block yet
+		color.Green(urlAPI + "/blocks/genesis")
+		res, err := http.Get(urlAPI + "/blocks/genesis")
+		check(err)
+		body, err := ioutil.ReadAll(res.Body)
+		check(err)
+		err = json.Unmarshal(body, &block)
+		check(err)
+		color.Yellow("[New Block]: " + block.Hash)
+		err = bc.AddBlock(block)
+		check(err)
+	} else {
+		block.NextHash = h
+	}
+
+	for block.NextHash != "" && block.Hash != "" {
+		res, err := http.Get(urlAPI + "/blocks/next/" + block.Hash)
+		check(err)
+		body, err := ioutil.ReadAll(res.Body)
+		check(err)
+		err = json.Unmarshal(body, &block)
+		check(err)
+		if block.Hash != "" {
+			color.Yellow("[New Block]: " + block.Hash)
+			err = bc.AddBlock(block)
+			check(err)
+		}
+	}
+	bc.Print()
+}
+
+func (bc *Blockchain) Print() {
+	color.Green("Printing Blockchain stored in memory")
+	color.Green("Genesis Block: " + bc.GenesisBlock)
+	for _, b := range bc.Blocks {
+		color.Green("Block height:")
+		fmt.Println(b.Height)
+		color.Green("Hash: " + b.Hash)
+		color.Green("Date: " + b.Date.String())
+		color.Green("---")
+	}
+}
+
+func (bc *Blockchain) ReadFromDisk() error {
+	file, err := ioutil.ReadFile("blockchain.data")
+	if err != nil {
+		return err
+	}
+	content := string(file)
+	json.Unmarshal([]byte(content), &bc)
+	return nil
+}
+
+func (bc *Blockchain) SaveToDisk() error {
+	bytesBlockchain, err := json.Marshal(bc)
+	if err != nil {
+		return err
+	}
+	err = ioutil.WriteFile("blockchain.data", bytesBlockchain, 0644)
+	if err != nil {
+		return err
+	}
+	return nil
+}

peer/blockchainlib/errors.go

@@ -0,0 +1,15 @@
+package blockchainlib
+
+import (
+	"log"
+	"runtime"
+)
+
+func check(err error) {
+	if err != nil {
+		_, fn, line, _ := runtime.Caller(1)
+		log.Println(line)
+		log.Println(fn)
+		log.Println(err)
+	}
+}