123 lines
3.1 KiB
Python
123 lines
3.1 KiB
Python
import hashlib
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import logging
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from datetime import datetime
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from database import Block, db
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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 necessary
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if not self.get_blocks(0):
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self.new_block(previous_hash='1', proof=100)
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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 of the block is correct
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if block['previous_hash'] != self.hash(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 new_block(self, proof, previous_hash):
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"""
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Create a new Block in the Blockchain
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:param proof: The proof given by the Proof of Work algorithm
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:param previous_hash: Hash of previous Block
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:param height: The Height of the new block
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:return: New Block
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"""
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block = Block(
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timestamp=datetime.now(),
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transactions=self.current_transactions,
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proof=proof,
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previous_hash=previous_hash,
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)
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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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return block
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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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@staticmethod
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def hash(block):
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"""
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Creates a SHA-256 hash of a Block
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:param block: Block
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"""
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block_bytes = block.to_json().encode()
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return hashlib.sha256(block_bytes).hexdigest()
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