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')