การพัฒนาบล็อกเชนด้วย Python: การสร้างสกุลเงินดิจิทัลสกุลแรกของคุณ

            
import hashlib
import json
from time import time
from urllib.parse import urlparse
import uuid
import requests

            

              
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class Block:
    def __init__(self, index, timestamp, transactions, previous_hash):
        self.index = index
        self.timestamp = timestamp
        self.transactions = transactions
        self.previous_hash = previous_hash
        self.hash = self.calculate_hash()

    def calculate_hash(self):
        block_string = json.dumps({
            "index": self.index,
            "timestamp": self.timestamp,
            "transactions": self.transactions,
            "previous_hash": self.previous_hash
        }, sort_keys=True).encode()
        return hashlib.sha256(block_string).hexdigest()

            

              
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class Blockchain:
    def __init__(self):
        self.chain = []
        self.current_transactions = []
        # Create the genesis block
        self.new_block(previous_hash='1', index=0) # Genesis block has index 0

    def new_block(self, previous_hash=None, index=None):
        # Creates a new Block and adds it to the chain
        block = Block(index or len(self.chain) + 1,
                      time(),
                      self.current_transactions,
                      previous_hash or self.hash(self.chain[-1]))

        # Reset current transactions
        self.current_transactions = []
        self.chain.append(block)
        return block

    def new_transaction(self, sender, recipient, amount):
        # Adds a new transaction to the list of transactions for the next block
        self.current_transactions.append({
            'sender': sender,
            'recipient': recipient,
            'amount': amount,
        })
        return self.last_block['index'] + 1

    def hash(self, block):
        # Hashes a block
        block_string = json.dumps({
            "index": block.index,
            "timestamp": block.timestamp,
            "transactions": block.transactions,
            "previous_hash": block.previous_hash
        }, sort_keys=True).encode()
        return hashlib.sha256(block_string).hexdigest()

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

            

              
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from flask import Flask, jsonify, request

app = Flask(__name__)

# Generate a unique node identifier
node_identifier = str(uuid.uuid4()).replace('-', '')

# Instantiate the Blockchain
blockchain = Blockchain()

@app.route('/mine', methods=['GET'])
def mine():
    # We need to add a new transaction to reward the miner
    # For simplicity, let's assume a hardcoded reward transaction
    # In a real crypto, this would be more complex (e.g., from a special address)
    blockchain.new_transaction(sender="0", recipient=node_identifier, amount=1)

    # Forge the new Block
    previous_block = blockchain.last_block
    previous_hash = blockchain.hash(previous_block)
    index = len(blockchain.chain) + 1
    block = blockchain.new_block(index=index, previous_hash=previous_hash)

    response = {
        'message': "New Block Forged",
        'index': block.index,
        'transactions': block.transactions,
        'hash': block.hash,
    }
    return jsonify(response), 200

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

    # Check that the required fields are in the POST's JSON data
    required = ['sender', 'recipient', 'amount']
    if not all(k in values for k in required):
        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': [vars(block) for block in blockchain.chain],
        'length': len(blockchain.chain),
    }
    return jsonify(response), 200

@app.route('/nodes/register', methods=['POST'])
def register_nodes():
    values = request.get_json()

    nodes = values.get('nodes')
    if nodes is None:
        return "Error: Please supply a valid list of nodes", 400

    for node in nodes:
        blockchain.register_node(node)

    response = {
        'message': 'New nodes have been added',
        'total_nodes': list(blockchain.nodes),
    }
    return jsonify(response), 201

@app.route('/nodes/resolve', methods=['GET'])
def consensus():
    # This is a simplified consensus algorithm. In a real blockchain,
    # this would involve complex logic to find the longest valid chain.
    # For this example, we'll just resolve conflicts by choosing the longest chain.
    replaced = blockchain.resolve_conflicts()

    if replaced:
        response = {
            'message': 'Our chain was replaced',
            'new_chain': [vars(block) for block in blockchain.chain],
        }
    else:
        response = {
            'message': 'Our chain is authoritative',
        }

    return jsonify(response), 200

if __name__ == '__main__':
    # To run this, you'd typically run multiple instances on different ports
    # For example: python your_script.py -p 5000
    # And then: python your_script.py -p 5001 (and so on)
    # You would then register nodes with each other.
    app.run(host='0.0.0.0', port=5000)

            

              
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class Blockchain:
    def __init__(self):
        self.chain = []
        self.current_transactions = []
        self.new_block(previous_hash='1', index=0) # Genesis block
        self.nodes = set() # To store our network nodes
        self.difficulty = 4 # Number of leading zeros required for the hash

    def register_node(self, address):
        '''Adds a new node to the list of nodes'''
        parsed_url = urlparse(address)
        self.nodes.add(parsed_url.netloc)

    def valid_proof(self, last_proof, proof):
        guess = f'{last_proof}{proof}'.encode()
        guess_hash = hashlib.sha256(guess).hexdigest()
        return guess_hash[:self.difficulty] == "0" * self.difficulty

    def proof_of_work(self, last_proof):
        # Simple Proof of Work Algorithm:
        # - Find a number p' such that hash(pp') contains leading 4 zeroes,
        # where p is the previous proof, and p' is a new proof
        proof = 0
        while self.valid_proof(last_proof, proof) == False:
            proof += 1
        return proof

    def new_block(self, index=None, previous_hash=None, proof=None):
        # Creates a new Block and adds it to the chain
        block = Block(index or len(self.chain) + 1,
                      time(),
                      self.current_transactions,
                      previous_hash or self.hash(self.chain[-1]))

        # Proof of Work validation
        last_block_proof = self.chain[-1].proof if len(self.chain) > 0 else 0
        if proof is None:
             proof = self.proof_of_work(last_block_proof)

        block.proof = proof
        block.hash = self.hash(block)

        # Reset current transactions
        self.current_transactions = []
        self.chain.append(block)
        return block

    def new_transaction(self, sender, recipient, amount):
        # Adds a new transaction to the list of transactions for the next block
        # Ensure sender and recipient are not the same to prevent self-transactions
        if sender == recipient:
            raise ValueError("Sender and recipient cannot be the same.")
        # Basic check for valid amount, in a real system, more checks are needed.
        if not isinstance(amount, (int, float)) or amount <= 0:
            raise ValueError("Amount must be a positive number.")

        self.current_transactions.append({
            'sender': sender,
            'recipient': recipient,
            'amount': amount,
        })
        return self.last_block.index + 1

    def hash(self, block):
        # Hashes a block, including its proof
        block_string = json.dumps({
            "index": block.index,
            "timestamp": block.timestamp,
            "transactions": block.transactions,
            "previous_hash": block.previous_hash,
            "proof": block.proof
        }, sort_keys=True).encode()
        return hashlib.sha256(block_string).hexdigest()

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

    # ... (add the rest of the methods like resolve_conflicts, valid_chain etc. and update Flask routes accordingly)

            

              
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@app.route('/mine', methods=['GET'])
def mine():
    # In a real cryptocurrency, the miner would be rewarded here.
    # For simplicity, we'll add a transaction that rewards the node itself.
    # The sender "0" is a convention for newly minted coins.
    blockchain.new_transaction(sender="0", recipient=node_identifier, amount=1) # Reward for mining

    # Get the last block's proof
    last_block = blockchain.last_block
    last_proof = last_block.proof

    # Find the next proof through Proof of Work
    proof = blockchain.proof_of_work(last_proof)

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

    response = {
        'message': "New Block Forged",
        'index': block.index,
        'transactions': block.transactions,
        'proof': block.proof,
        'hash': block.hash,
    }
    return jsonify(response), 200

            

              
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    def register_node(self, address):
        '''Adds a new node to the list of nodes'''
        parsed_url = urlparse(address)
        self.nodes.add(parsed_url.netloc)

            

              
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    def valid_chain(self, chain):
        '''Determine if a given blockchain is valid'''
        last_block = chain[0]
        current_index = 1

        while current_index < len(chain):
            block = chain[current_index]
            # Check if the block's previous hash is correct
            if block.previous_hash != self.hash(last_block):
                return False

            # Check if the Proof of Work is correct
            if not self.valid_proof(last_block.proof, block.proof):
                return False

            last_block = block
            current_index += 1

        return True

    def resolve_conflicts(self):
        '''
        This is our consensus algorithm used to resolve conflicts.
        It chooses the longest valid chain.
        '''
        neighbours = self.nodes
        new_chain = None

        # Grab and verify the chains from all the other nodes
        for node in neighbours:
            try:
                response = requests.get(f'http://{node}/chain')

                if response.status_code == 200:
                    length = response.json()['length']
                    chain = response.json()['chain']

                    # Convert received chain data back into Block objects for validation
                    # (This is a simplification; real systems might have more robust serialization)
                    parsed_chain = []
                    for block_data in chain:
                        # Create a dummy block to hash against previous block
                        # Note: In a full implementation, you'd reconstruct the Block object
                        # This simplification assumes the data is directly usable for validation check
                        # A more robust solution would involve a Block class constructor that takes dict
                        dummy_block_for_hashing = type('obj', (object,), block_data)()
                        parsed_chain.append(dummy_block_for_hashing)

                    # Check if the chain is longer and valid
                    if length > len(self.chain) and self.valid_chain(parsed_chain):
                        new_chain = parsed_chain
            except requests.exceptions.RequestException as e:
                print(f"Error fetching chain from node {node}: {e}")
                continue # Move to the next node if there's an error

        # Replace our chain if we discovered a new, valid chain longer than ours
        if new_chain:
            # Reconstruct the actual chain based on the longest one found.
            # This part requires careful handling of Block object reconstruction.
            # For this simplified example, we'll assume the parsed_chain can be directly used.
            # In a production system, you'd map block_data back to your Block class properly.
            self.chain = new_chain # This assignment might need careful object mapping
            return True

        return False

            

              
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@app.route('/nodes/resolve', methods=['GET'])
def consensus():
    replaced = blockchain.resolve_conflicts()

    if replaced:
        response = {
            'message': 'Our chain was replaced',
            'chain': [vars(block) for block in blockchain.chain],
        }
    else:
        response = {
            'message': 'Our chain is authoritative',
        }

    return jsonify(response), 200

            

              
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