def is_valid_transaction_chain(chain): """ Enforce the rules of a chain composed of blocks of transactions - each transaction must only appear once in the chain - There can be only one mining reward per block - Each transaction must be valid """ transaction_ids = set() for i in range(len(chain)): block = chain[i] has_mining_reward = False for transaction_json in block.data: transaction = Transaction.from_json(transaction_json) if transaction.id in transaction_ids: raise Exception(f'Transaction: {transaction.id} is not unique') transaction_ids.add(transaction.id) if transaction.input == MINING_REWARD_INPUT: if has_mining_reward: raise Exception(f'There can be only one mining reward per block check this block: {block.hash}') has_mining_reward = True else: historic_blockchain = Blockchain() historic_blockchain.chain = chain[0:i] historic_balance = Wallet.calculate_balance(historic_blockchain, transaction.input['address']) if historic_balance != transaction.input['amount']: raise Exception(f'Transaction {transaction.id} has '\ 'invalid input amount') Transaction.transaction_is_valid(transaction)
def message(self, pubnub, msg_obj): print( f'\n-- Incoming Channel: {msg_obj.channel} | message: {msg_obj.message}' ) if msg_obj.channel == CHANNELS['BLOCK']: block = Block.from_json(msg_obj.message) potential_chain = self.blockchain.chain[:] potential_chain.append(block) try: self.blockchain.replace_chain(potential_chain) self.transaction_pool.clear_blockchain_transactions( self.blockchain) print('successfullt replaced the chaihn') except Exception as e: print(f'\n -- Did not replace chain {e}') elif msg_obj.channel == CHANNELS['TRANSACTION']: transaction = Transaction.from_json(msg_obj.message) self.transaction_pool.set_transaction(transaction) print('\n-- Set the new transaction in the transaction pool')