import hashlib
x = 11
y = 1
#这里可以调节挖矿难度，也就是哈希的长度
while hashlib.sha256(f'{x*y}'.encode("utf-8")).hexdigest()[5:7]!="00":
  print(x*y)
  y +=1
print("找到了：",(x*y))

#挖矿原理与网络共识
import datetime
import hashlib
import json
import requests

class Blockchain2:

  def __init__(self):
    self.chain = [] #区块链列表
    self.nodes = set() #节点集合
    self.current_tranactions = [] #交易列表
    self.new_block(proof=100,preHash=1) #创建第一个区块

  #新建一个区块，需要计算，才能追加
  def new_block(self,proof,preHash = None):
    block={
      "index":len(self.chain)+1,#区块索引
      "timestamp":datetime.datetiem.now(),#区块时间戳
      "transactions":self.current_tranactions,#区块交易记录集合
      "proof":proof,#算力凭证
      "preHash":preHash or self.hash(self.chain[-1]), #上一块的哈希
    }
    self.current_tranactions = [] #开辟新的区块，初始化区块交易记录
    self.chain.append(block)

  @staticmethod
  def hash(block):
    #处理为json字符串格式的哈希
    block_str = json.dumps(block,sort_keys=True).encode("utf-8")
    return hashlib.sha256(block_str).hexdigest()

  #新增交易记录
  def new_transaction(self,sender,receiver,amount):
    transaction ={
      "sender":sender,
      "receiver":receiver,
      "amount":amount,
    }

    self.current_tranactions.append(transaction)

    return self.last_block["index"]+1

  @property
  def last_block(self):
    return self.chain[-1]

  #挖矿，依赖上一个模块，获取工作量证明，即POW共识机制
  def proof_of_work(self,last_block):
    last_proof = last_block["proof"]
    last_hash = self.hash(last_block)
    proof = 0

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

    return proof

  #校验工作量
  @staticmethod
  def valid_proof(last_proof,proof,last_hash):
    guess = f'{last_proof}{proof}{last_hash}'.encode("utf-8")
    guess_hash = hashlib.sha256(guess).hexdigest()
    return guess_hash[:6] =="000000" #可以调整计算难度

  #区块一致性，同步算法,
  def resolve_conflicts(self):
    neighbours = self.nodes
    new_chain = None
    max_length = len(self.chain)
    #遍历所有节点，找出最长的链
    for node in neighbours:
      #获取节点区块链信息
      response = requests.get(f'http://{node}/chain')
      if response.status_code ==200:
        length = response.json()["length"]
        chain = response.json()["chain"]

        if length>max_length and self.valid_chain(chain):
          max_length = length
          new_chain = chain

    if new_chain:
      self.chain = new_chain
      return True
    else:
      return False

  #校验区块链的合法性
  def valid_chain(self,chain):
    last_block = chain[0]
    current_index = 1
    #校验每一个区块的prehash,proof合法性
    while current_index <len(chain):
      block = chain[current_index]
      #校验哈希的合法性
      if block["preHash"] != self.hash(last_block):
        return False
      #校验算力的合法性
      if not self.valid_proof(last_block["proof"],block["proof"],block["preHash"]):
        return False
      last_block = block
      current_index +=1
    return True