blockchain.py

import datetime
import hashlib
import math 
import json
from operator import truediv
from flask import Flask,jsonify
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    

app =Flask(__name__)

blockchain = Blockchain()

@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':'congragulate,you just mined a block',
                 'index':block['index'],
                 'timestamp':block['timestamp'],
                 'proof': block['proof'],
                 'previous_hash' : block['previous_hash']}
    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



if __name__ == '__main__':
    app.debug = True
    app.run(host= '0.0.0.0',port = 5000)