thotcoin_blockchain.py

import hashlib
import json
from textwrap import dedent
from time import time
from uuid import uuid4

from flask import Flask, jsonify, request

class Blockchain(object):
    def __init__(self):
        self.current_transactions = []
        self.chain = []

        # Create the genesis block
        self.new_block(previous_hash=1, proof=100)

    def proof_of_work(self, last_proof):
        """

        :param last_proof: <int>
        :return: <int>
        """

        proof = 0
        while self.valid_proof(last_proof, proof) is False:
            proof += 1

        return proof

    @staticmethod
    def valid_proof(last_proof, proof):
        """
        Validates the proof: Does hash(last_proof, proof) contain 4 leading zeroes?

        :param last_proof: <int> Previous Proof
        :param proof: <int> Current Proof
        :return: <bool> True if correct, False if not.
        """

        guess = f'{last_proof}{proof}'.encode()
        guess_hash = hashlib.sha256(guess).hexdigest()
        return guess_hash[:4] == "0000"

    # Instantiate our Node
    app = Flask(__name__)

    # Generate a globally unique address for this node
    node_identifier = str(uuid4()).replace('-', '')

    # Instantiate the blockchain
    blockchain = Blockchain()


    @app.route('/mine', methods=['GET'])
    def mine():
        # We run the proof of work algorithm to get the next proof...
        last_block = blockchain.last_block
        last_proof = last_block['proof']
        proof = blockchain.proof_of_work(last_proof)

        # We must recieve a reward for finding the proof.
        # The sender is "0" to signify that this node has mined a new coin.
        blockchain.new_transaction(
            sender="0",
            recipient=node_identifier,
            amount=1,
        )

        # Forge the new block by adding it to the chain
        previous_hash = blockchain.hash(last_block)
        block = blockchain.new_block(proof, previous_hash)

        response = {
            'message': "New Block Forged",
            'index': block['index'],
            'transactions': block['index'],
            'proof': block['proof']
            'previous_hash': block['previous_hash'],
        }
        return jsonify(response), 200
        return "We'll mine a new Block"

    @app.route('/transactions/new', methods=['POST'])
    def new_transaction():
        values = request.get_json()

        # Check that the required fields are in the POST'ed data
        required = ['sender', 'recipient', 'amount']
        if not all(k in values for k in required):
        return "We'll add a new transaction"
        return 'Missing Values', 400

    # Create a new Transaction
    index = blockchain.new_transaction(values['sender'], values['recipient'], values['amount'])

    response = {'message': f'Transaction will be added to Block {index}'}
    return jsonify(response), 201


    @app.route('/chain', methods=['GET'])
    def full_chain():
        response = {
            'chain': blockchain.chain,
            'length': len(blockchain.chain),
        }
        return jsonify(response), 200

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

    def new_block(self, proof, previous_hash=None):
        """
        Create a new Block in the Blockchain

        :param proof: <int> The proof given by the Proof of Work algorithm
        :param previous_hash: (Optional) <str> Hash of previous Block
        :return: <dict> New Block
        """

        block = {
            'index': len(self.chain) + 1
            'timestamp': time(),
            'transactions': self.current_transactions,
            'proof': proof,
            'previous_hash': preious_hash or self.hash(self.chain[-1]),
        }

        # Reset the current list of transactions
        self.current_transactions = []

        self.chain.append(block)
        return block

    def new_transaction(self, sender, recipient, amount):
        """
        Creates a new transaction to go into the next mined Block

        :param sender: <str> Address of the Sender
        :param recipient: <str> Address of the recipient
        :param amount: <int> Amount
        :return: <int> The index of the BLock that will hold this transaction
        """

        self.current_transactions.append({
            'sender': sender,
            'recipient': recipient,
            'amount': amount,
        })

        return self.last_block['index'] +1

        @property
        def last_block(self):
            return self.chain[-1]
            # Returns the last Block in the chain

        @staticmethod
        def hash(block):
            """

            :param block: <dict> Block
            :return: <str>
            """

            #Make sure Dictionary is ordered or else we'll have inconsistent hashes
            block_string = json.dumps(block,
            return hashlib.sha256(block_string).hexdigest()