119 lines
3.2 KiB
Python
119 lines
3.2 KiB
Python
import logging
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from datetime import datetime
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from database import Block, db
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from helpers import hash_block
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logger = logging.getLogger('root.blockchain')
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class Blockchain:
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def __init__(self):
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self.current_transactions = []
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self.difficulty = 4
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# Create the genesis block if it doesn't exist
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if not self.last_block:
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block = self.build_block()
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block['hash'] = hash_block(block)
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self.save_block(block)
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logger.info("✨ Created genesis block")
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logger.info("Blockchain Initiated")
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@staticmethod
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def get_blocks(height=0):
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"""
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Returns all blocks from a given height
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:param height: <int> The height from which to return blocks
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:return:
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"""
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blocks = db.query(Block).filter(Block.height >= height).all()
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return [block.to_dict() for block in blocks]
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def valid_chain(self, chain):
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"""
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Determines if a given blockchain is valid
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:param chain: A blockchain
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:return: True if valid, False if not
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"""
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last_block = chain[0]
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current_index = 1
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while current_index < len(chain):
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block = chain[current_index]
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# Check that the hash_block of the block is correct
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if block['previous_hash'] != self.hash_block(last_block):
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return False
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# Check that the Proof of Work is correct
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if not self.valid_proof(last_block['proof'], block['proof']):
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return False
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last_block = block
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current_index += 1
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return True
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def build_block(self):
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"""
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Create a new Block in the Blockchain
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"""
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last_block = self.last_block
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return {
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'height': last_block.height + 1 if last_block else 0,
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'timestamp': datetime.utcnow(),
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'transactions': self.current_transactions,
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'previous_hash': last_block.hash if last_block else 0,
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'proof': -1,
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}
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def save_block(self, block_dict):
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"""
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Saves Block to the database and resets outstanding transactions
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:param block_dict: A dictionary representation of a Block
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:return:
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"""
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print(block_dict)
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block = Block(**block_dict)
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db.add(block)
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db.commit()
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# Reset the current list of transactions
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self.current_transactions = []
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def new_transaction(self, sender, recipient, amount):
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"""
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Creates a new transaction to go into the next mined Block
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:param sender: Address of the Sender
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:param recipient: Address of the Recipient
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:param amount: Amount
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:return: The index of the Block that will hold this transaction
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"""
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self.current_transactions.append({
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'sender': sender,
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'recipient': recipient,
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'amount': amount,
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})
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return self.last_block['index'] + 1
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@property
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def last_block(self):
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"""
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Returns the last block in the Blockchain (greatest height)
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:return: <Block>
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"""
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return db.query(Block).order_by(Block.height.desc()).first()
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