blockshell/blockchain/chain.py

# -*- coding: utf-8 -*-
# ===================================================
# ==================== META DATA ===================
# ==================================================
__author__ = "Daxeel Soni"
__url__ = "https://daxeel.github.io"
__email__ = "daxeelsoni44@gmail.com"
__license__ = "MIT"
__version__ = "0.1"
__maintainer__ = "Daxeel Soni"

# ==================================================
# ================= IMPORT MODULES =================
# ==================================================
import os
import hashlib
import datetime
import json
from colorama import Fore, Back, Style
import time
import sys
import base64
from numpy import random
from PIL import Image

# ==================================================
# =================== BLOCK CLASS ==================
# ==================================================
class Block:
    """
        Create a new block in chain with metadata
    """
    def __init__(self):
        self.index = -1
        self.previousHash = ""
        self.uid_epita = -1
        self.email_epita = ""
        self.firstname = ""
        self.lastname = ""
        self.image = ""
        self.timestamp = str(datetime.datetime.now())
        self.nonce = 0
        self.hash = self.calculateHash()

    @classmethod
    def fromSave(cls, data):
        block = cls()

        for key, value in data.items():
            setattr(block, key, value)
        
        return block

    @classmethod
    def fromValues(cls, uid_epita, email_epita, firstname, lastname, index = 0):
        block = cls()

        block.index = index
        block.uid_epita = uid_epita
        block.email_epita = email_epita
        block.firstname = firstname
        block.lastname = lastname
        block.createRandomImage()
        
        return block

    def calculateHash(self):
        """
            Method to calculate hash from metadata
        """
        hashData = str(self.index) + str(self.previousHash) + str(self.uid_epita) + str(self.email_epita) + str(self.firstname) + str(self.lastname) + str(self.image) + str(self.timestamp) + str(self.nonce)
        return hashlib.sha256(hashData.encode('utf-8')).hexdigest()

    def mineBlock(self, difficulty):
        """
            Method for Proof of Work
        """
        print(Back.RED + "\n[Status] Mining block (" + str(self.index) + ") with PoW ...")
        startTime = time.time()
        self.hash = ""

        while self.hash[:difficulty] != "0"*difficulty:
            self.nonce += 1
            self.hash = self.calculateHash()

        endTime = time.time()
        print(Back.BLUE + "[ Info ] Time Elapsed : " + str(endTime - startTime) + " seconds.")
        print(Back.BLUE + "[ Info ] Mined Hash : " + self.hash)
        print(Style.RESET_ALL)

    def createRandomImage(self):
        """
            Method to create random image in base64
        """
        imgarray = random.rand(30, 30, 3) * 255
        image = Image.fromarray(imgarray.astype('uint8')).convert('RGB')
        image.save('random.png')
        with open("random.png", "rb") as imageFile:
            self.image = str(base64.b64encode(imageFile.read()))
        if os.path.exists("random.png"):
            os.remove("random.png")
        

# ==================================================
# ================ BLOCKCHAIN CLASS ================
# ==================================================
class Blockchain:
    """
        Initialize blockchain
    """
    def __init__(self):
        self.chain = [self.createGenesisBlock()]
        self.difficulty = 3

    def createGenesisBlock(self):
        """
            Method create genesis block
        """
        return Block.fromValues(-1, "init@epita.fr", "Genesis", "Block")

    def addBlock(self, newBlock):
        """
            Method to add new block from Block class
        """
        newBlock.index = len(self.chain)
        newBlock.previousHash = self.chain[-1].hash
        newBlock.mineBlock(self.difficulty)
        self.chain.append(newBlock)
        self.writeBlocks()

    def writeBlocks(self):
        """
            Method to write new mined block to blockchain
        """
        with open("chain.txt", "w") as dataFile:
            chainData = []
            for eachBlock in self.chain:
                chainData.append(eachBlock.__dict__)
            dataFile.write(json.dumps(chainData, indent=4))

    def loadBlocks(self, filename):
        """
            Method to load existing blockchain from file
        """
        try:
            with open(filename, "r") as dataFile:
                chainData = json.loads(dataFile.read())
            self.chain = []
            for eachBlock in chainData:
                self.chain.append(Block.fromSave(eachBlock))
        except Exception as e:
            print(Back.RED + "[Error] No existing blockchain found.")
            print(Back.RED + "[Error] Creating new blockchain.")
            print(Style.RESET_ALL)
            self.writeBlocks()

    def modifyBlock(self, hash, uid_epita, email_epita, firstname, lastname):
        """
            Method to modify existing block
        """
        i = 0
        for i in range(len(self.chain)):
            eachBlock = self.chain[i]
            if eachBlock.hash == hash:
                eachBlock.uid_epita = uid_epita
                eachBlock.email_epita = email_epita
                eachBlock.firstname = firstname
                eachBlock.lastname = lastname
                eachBlock.createRandomImage()
                eachBlock.mineBlock(self.difficulty)
                break
        if i == len(self.chain) - 1:
            return False
        for i in range(i+1, len(self.chain)):
            eachBlock = self.chain[i]
            eachBlock.index = i
            eachBlock.previousHash = self.chain[i-1].hash
            eachBlock.mineBlock(self.difficulty)
            self.writeBlocks()
        return True

    def isChainValid(self):
        """
            Method to verify integrity of blockchain
        """
        for i in range(1, len(self.chain)):
            eachBlock = self.chain[i]
            if eachBlock.hash != eachBlock.calculateHash():
                return i
            if eachBlock.previousHash != self.chain[i-1].hash:
                return i
        return 0