chain.py

import os

import hashlib
import time
import json

class Blockchain(object):
  def __init__(self):
    self._chain_list = [] # initialize empty list

  def add_block_to_chain(self, block):
    self._chain_list.append(block)
    #self.check_chain_validity()

  def add_genesis_block(self, block):
    self._chain_list.append(block)

  def get_latest_block(self):
    return self._chain_list[-1]

  def get_total_blocks(self):
    return len(self._chain_list)

  def check_chain_validity(self):
    previous_hash = "0"

    for block in self._chain_list:
      if str(previous_hash) != str(block.prev_hash):
        print("Block #" + str(block.index - 1) + " in not valid")
      
      previous_hash = block.calculate_block_hash()  

  def load(self):
    for _, _, files in os.walk("chain/"):
      for file in files:
        with open("chain/" + file, 'r', encoding='utf-8') as json_file:
          data = json.load(json_file)
          book = Book(data['book_info']['name'],
                      data['book_info']['author'], 
                      data['book_info']['publishing_company'], 
                      data['book_info']['rent_owner'],
                      data['book_info']['rent_timestamp'])

          block = Block(data['index'], data['timestamp'], book)
          block.prev_hash = data['prev_hash']

          self.add_block_to_chain(block)

class Block(object):
  def __init__(self, index, timestamp, book_info):
    self.index = index
    
    self.prev_hash = "0"
    if chain.get_total_blocks() != 0:
      self.prev_hash = chain.get_latest_block().calculate_block_hash()

    self.timestamp = timestamp or time.time()
    self.book_info = book_info

    self.data = {
        'index': self.index,
        'timestamp': self.timestamp,
        'block_hash': self.calculate_block_hash(),
        'prev_hash': self.prev_hash,
        'book_info': self.book_info.get_data()
    }
    file_path = "chain/" + str(self.index) + '.txt'
    if not os.path.isfile(file_path):
      with open(file_path, 'w', encoding='utf-8') as file:
        json.dump(self.data, file, indent=3, ensure_ascii=False)

      print("Block " + str(self.index) + " saved")

  def calculate_block_hash(self):
    return hashlib.sha256(bytearray(str(self.index) + str(self.timestamp) + str(self.prev_hash) + self.book_info.get_hash(), "utf-8")).hexdigest()

class Book(object):
  def __init__(self, name, author, publishing_company, rent_owner, rent_timestamp=0):
    self.name = name
    self.author = author
    self.publishing_company = publishing_company
    self.rent_owner = rent_owner
    self.rent_timestamp = rent_timestamp or time.time()

  def get_hash(self):
    return hashlib.sha256(bytearray(str(self.name)
                                    + str(self.author)
                                    + str(self.publishing_company)
                                    + str(self.rent_owner)
                                    + str(self.rent_timestamp), "utf-8")).hexdigest()

  def get_data(self):
    return {
        'name': self.name,
        'author': self.author,
        'publishing_company': self.publishing_company,
        'rent_owner': self.rent_owner,
        'rent_timestamp': self.rent_timestamp,
    }

if __name__ == "__main__":
  print('Initializing blockchain')
  chain = Blockchain()

  if len(os.listdir("chain/")) == 0:
    print('Generate new blocks')
    genesis_book = Book("Два капитана", "Каверин", "ХЗ", "None")
    genesis_block = Block(chain.get_total_blocks(), time.time(), genesis_book)
    chain.add_genesis_block(genesis_block)

    books = {
      Book("Бойцовский клуб", "Чак Паланик", "АСТ", "None"),
      Book("Дневник памяти", "Николас Спаркс", "АСТ", "None"),
      Book("Поющие в терновнике", "Маккалоу Колин", "АСТ", "None"),
      Book("Зеленая миля", "Кинг Стивен", "АСТ", "None"),
      Book("Крутой поворот", "Спаркс Николас", "АСТ", "None"),
    }

    for book in books:
      block = Block(chain.get_total_blocks(), time.time(), book)
      
      chain.add_block_to_chain(block)
  else:
    print('Loading exist\'s block\'s')
    chain.load()
  
  print('Total blocks: ' + str(chain.get_total_blocks()))
  chain.check_chain_validity()
  
import os

import hashlib
import time
import json

class Blockchain(object):
  def __init__(self):
    self._chain_list = [] # initialize empty list

  def add_block_to_chain(self, block):
    self._chain_list.append(block)
    #self.check_chain_validity()

  def add_genesis_block(self, block):
    self._chain_list.append(block)

  def get_latest_block(self):
    return self._chain_list[-1]

  def get_total_blocks(self):
    return len(self._chain_list)

  def check_chain_validity(self):
    previous_hash = "0"

    for block in self._chain_list:
      if str(previous_hash) != str(block.prev_hash):
        print("Block #" + str(block.index - 1) + " in not valid")
      
      previous_hash = block.calculate_block_hash()  

  def load(self):
    for _, _, files in os.walk("chain/"):
      for file in files:
        with open("chain/" + file, 'r', encoding='utf-8') as json_file:
          data = json.load(json_file)
          book = Book(data['book_info']['name'],
                      data['book_info']['author'], 
                      data['book_info']['publishing_company'], 
                      data['book_info']['rent_owner'],
                      data['book_info']['rent_timestamp'])

          block = Block(data['index'], data['timestamp'], book)
          block.prev_hash = data['prev_hash']

          self.add_block_to_chain(block)

class Block(object):
  def __init__(self, index, timestamp, book_info):
    self.index = index
    
    self.prev_hash = "0"
    if chain.get_total_blocks() != 0:
      self.prev_hash = chain.get_latest_block().calculate_block_hash()

    self.timestamp = timestamp or time.time()
    self.book_info = book_info

    self.data = {
        'index': self.index,
        'timestamp': self.timestamp,
        'block_hash': self.calculate_block_hash(),
        'prev_hash': self.prev_hash,
        'book_info': self.book_info.get_data()
    }
    file_path = "chain/" + str(self.index) + '.txt'
    if not os.path.isfile(file_path):
      with open(file_path, 'w', encoding='utf-8') as file:
        json.dump(self.data, file, indent=3, ensure_ascii=False)

      print("Block " + str(self.index) + " saved")

  def calculate_block_hash(self):
    return hashlib.sha256(bytearray(str(self.index) + str(self.timestamp) + str(self.prev_hash) + self.book_info.get_hash(), "utf-8")).hexdigest()

class Book(object):
  def __init__(self, name, author, publishing_company, rent_owner, rent_timestamp=0):
    self.name = name
    self.author = author
    self.publishing_company = publishing_company
    self.rent_owner = rent_owner
    self.rent_timestamp = rent_timestamp or time.time()

  def get_hash(self):
    return hashlib.sha256(bytearray(str(self.name)
                                    + str(self.author)
                                    + str(self.publishing_company)
                                    + str(self.rent_owner)
                                    + str(self.rent_timestamp), "utf-8")).hexdigest()

  def get_data(self):
    return {
        'name': self.name,
        'author': self.author,
        'publishing_company': self.publishing_company,
        'rent_owner': self.rent_owner,
        'rent_timestamp': self.rent_timestamp,
    }

if __name__ == "__main__":
  print('Initializing blockchain')
  chain = Blockchain()

  if len(os.listdir("chain/")) == 0:
    print('Generate new blocks')
    genesis_book = Book("Два капитана", "Каверин", "ХЗ", "None")
    genesis_block = Block(chain.get_total_blocks(), time.time(), genesis_book)
    chain.add_genesis_block(genesis_block)

    books = {
      Book("Бойцовский клуб", "Чак Паланик", "АСТ", "None"),
      Book("Дневник памяти", "Николас Спаркс", "АСТ", "None"),
      Book("Поющие в терновнике", "Маккалоу Колин", "АСТ", "None"),
      Book("Зеленая миля", "Кинг Стивен", "АСТ", "None"),
      Book("Крутой поворот", "Спаркс Николас", "АСТ", "None"),
    }

    for book in books:
      block = Block(chain.get_total_blocks(), time.time(), book)
      
      chain.add_block_to_chain(block)
  else:
    print('Loading exist\'s block\'s')
    chain.load()
  
  print('Total blocks: ' + str(chain.get_total_blocks()))
  chain.check_chain_validity()