import hashlib
import json
from time import time
from typing import Any, Dict, List, Optional
from urllib.parse import urlparse
from uuid import uuid4import requests
from flask import Flask, jsonify, requestclass Blockchain:def __init__(self):self.current_transactions = []self.chain = []self.nodes = set()# 创建创世块self.new_block(previous_hash='1', proof=100)def register_node(self, address: str) -> None:"""Add a new node to the list of nodes:param address: Address of node. Eg. 'http://192.168.0.5:5000'"""parsed_url = urlparse(address)self.nodes.add(parsed_url.netloc)def valid_chain(self, chain: List[Dict[str, Any]]) -> bool:"""Determine if a given blockchain is valid:param chain: A blockchain:return: True if valid, False if not"""last_block = chain[0]current_index = 1while current_index < len(chain):block = chain[current_index]print(f'{last_block}')print(f'{block}')print("\n-----------\n")# Check that the hash of the block is correctif block['previous_hash'] != self.hash(last_block):return False# Check that the Proof of Work is correctif not self.valid_proof(last_block['proof'], block['proof']):return Falselast_block = blockcurrent_index += 1return Truedef resolve_conflicts(self) -> bool:"""共识算法解决冲突使用网络中最长的链.:return:  如果链被取代返回 True, 否则为False"""neighbours = self.nodesnew_chain = None# We're only looking for chains longer than oursmax_length = len(self.chain)# Grab and verify the chains from all the nodes in our networkfor node in neighbours:response = requests.get(f'http://{node}/chain')if response.status_code == 200:length = response.json()['length']chain = response.json()['chain']# Check if the length is longer and the chain is validif length > max_length and self.valid_chain(chain):max_length = lengthnew_chain = chain# Replace our chain if we discovered a new, valid chain longer than oursif new_chain:self.chain = new_chainreturn Truereturn Falsedef new_block(self, proof: int, previous_hash: Optional[str]) -> Dict[str, Any]:"""生成新块:param proof: The proof given by the Proof of Work algorithm:param previous_hash: Hash of previous Block:return: New Block"""block = {'index': len(self.chain) + 1,'timestamp': time(),'transactions': self.current_transactions,'proof': proof,'previous_hash': previous_hash or self.hash(self.chain[-1]),}# Reset the current list of transactionsself.current_transactions = []self.chain.append(block)return blockdef new_transaction(self, sender: str, recipient: str, amount: int) -> int:"""生成新交易信息，信息将加入到下一个待挖的区块中:param sender: Address of the Sender:param recipient: Address of the Recipient:param amount: Amount:return: 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@propertydef last_block(self) -> Dict[str, Any]:return self.chain[-1]@staticmethoddef hash(block: Dict[str, Any]) -> str:"""生成块的 SHA-256 hash值:param block: Block"""# We must make sure that the Dictionary is Ordered, or we'll have inconsistent hashesblock_string = json.dumps(block, sort_keys=True).encode()return hashlib.sha256(block_string).hexdigest()def proof_of_work(self, last_proof: int) -> int:"""简单的工作量证明:- 查找一个 p' 使得 hash(pp') 以4个0开头- p 是上一个块的证明,  p' 是当前的证明"""proof = 0while self.valid_proof(last_proof, proof) is False:proof += 1return proof@staticmethoddef valid_proof(last_proof: int, proof: int) -> bool:"""验证证明: 是否hash(last_proof, proof)以4个0开头:param last_proof: Previous Proof:param proof: Current Proof:return: True if correct, False if not."""guess = f'{last_proof}{proof}'.encode()guess_hash = hashlib.sha256(guess).hexdigest()return guess_hash[:4] == "0000"# Instantiate the 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_blocklast_proof = last_block['proof']proof = blockchain.proof_of_work(last_proof)# 给工作量证明的节点提供奖励.# 发送者为 "0" 表明是新挖出的币blockchain.new_transaction(sender="0",recipient=node_identifier,amount=1,)# Forge the new Block by adding it to the chainblock = blockchain.new_block(proof, None)response = {'message': "New Block Forged",'index': block['index'],'transactions': block['transactions'],'proof': block['proof'],'previous_hash': block['previous_hash'],}return jsonify(response), 200@app.route('/transactions/new', methods=['POST'])
def new_transaction():values = request.get_json()# 检查POST数据required = ['sender', 'recipient', 'amount']if not all(k in values for k in required):return 'Missing values', 400# Create a new Transactionindex = 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@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", 400for 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():replaced = blockchain.resolve_conflicts()if replaced:response = {'message': 'Our chain was replaced','new_chain': blockchain.chain}else:response = {'message': 'Our chain is authoritative','chain': blockchain.chain}return jsonify(response), 200if __name__ == '__main__':from argparse import ArgumentParserparser = ArgumentParser()parser.add_argument('-p', '--port', default=5000, type=int, help='port to listen on')args = parser.parse_args()port = args.portapp.run(host='127.0.0.1', port=port)