Blockchain-implementation-/blockchain.py at main · Compiler0110/Blockchain-implementation- · GitHub

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#Module 1 - Create a Blockchain


import datetime
import hashlib
import json
from flask import Flask, jsonify

# Building the Blockchain

class Blockchain:

    def __init__(self):
        self.chain = []
        self.create_block(proof=1,previous_hash = '0')

    def create_block(self , proof , previous_hash ):
        block = {
            'index' :len(self.chain) + 1 ,
            'timestamp' : str(datetime.datetime.now()),
            'proof' : proof,
            'previous_hash' : previous_hash}

        self.chain.append(block)
        return block

    def get_previous_block(self):
        return self.chain[-1]

    def proof_of_work(self, previous_proof):

        new_proof = 1
        check_proof = False

        while check_proof is False :

            hash_operation = hashlib.sha256(str(new_proof ** 2 - previous_proof**2).encode()).hexdigest()
            if hash_operation[:4] == '0000' :
                check_proof = True
            else :
                new_proof+=1

        return new_proof

    def hash(self,block):

        encoded_block = json.dumps(block, sort_keys= True).encode()
        return hashlib.sha256(encoded_block).hexdigest()


    def is_chain_valid(self,chain) :
        previous_block = chain[0]
        block_index = 1

        while block_index < len(chain):
            block = chain[block_index]
            if block['previous_hash'] != self.hash(previous_block):
                return False
            previous_proof = previous_block['proof']
            proof = block['proof']
            hash_operation = hashlib.sha256(str(proof ** 2 - previous_proof**2).encode()).hexdigest()
            if hash_operation[:4] != '0000' :
                return False
            previous_block = block
            block_index += 1
        return True


# creating web app

app = Flask(__name__)
app.config['JSONIFY_PRETTYPRINT_REGULAR'] = False
# creating blockchain

blockchain = Blockchain()

# mining blcokchain

@app.route('/mine_block',methods = ['GET'])


def mine_block():
    previous_block = blockchain.get_previous_block()
    previous_proof=  previous_block['proof']
    proof = blockchain.proof_of_work(previous_proof)
    previous_hash = blockchain.hash(previous_block)
    block = blockchain.create_block(proof, previous_hash)
    response = {'message' : 'congratulations,  you just mined a block',
                'index':block['index'],
                'timestamp':block['timestamp'],
                'proof':block['proof'],
                'previous_hash ': block['previous_hash']
                }
    return jsonify(response) , 200


#checing if the blockchain is valid
@app.route('/is_valid',methods = ['GET'])
def is_valid():

    is_valid = blockchain.is_chain_valid(blockchain.chain)

    if is_valid:
        response = {"Message" : "All good , the Blockchain is valid "}
    else :
        response = {"Huston , we have a problem. the blockchain is not valid "}

    return jsonify(response) , 200


@app.route('/get_chain',methods = ['GET'])

def get_chain():
    response = {'chain' : blockchain.chain ,
                'length ': len(blockchain.chain)
                }
    return jsonify(response) , 200


#running the app

app.run(host = '0.0.0.0', port = 5000)