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blockchain.py
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blockchain.py
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from functools import reduce
from json import dumps, loads
import pickle
import requests
from block import Block
from transaction import Transaction
from utility.hash_util import hash_block
from utility.verification import Verification
from wallet import Wallet
class Blockchain:
MINING_REWARD_SENDER = 'MINING REWARD'
MINING_REWARD = 10
def __init__(self, public_key, node_id):
genesis_block = Block(0, '', [], 100, 0)
self.__chain = [genesis_block]
self.__open_transactions = []
self.__peer_nodes = set()
self.public_key = public_key
self.node_id = node_id
self.resolve_conflicts = False
self.load_data()
@property
def chain(self):
return self.__chain[:]
@chain.setter
def chain(self, val):
pass
@property
def open_transactions(self):
return self.__open_transactions[:]
@open_transactions.setter
def open_transactions(self, val):
pass
def load_data(self, use_pickle=False):
if use_pickle:
try:
with open('blockchain-{}.p'.format(self.node_id), mode='rb') as file:
file_content = pickle.loads(file.read())
self.__chain = file_content['chain']
self.__open_transactions = file_content['ot']
except (IOError, IndexError):
print('File not found!')
else:
try:
with open('blockchain-{}.txt'.format(self.node_id), mode='r') as file:
file_content = file.readlines()
blockchain = loads(file_content[0][:-1])
updated_blockchain = []
for block in blockchain:
transactions = [Transaction(tx['sender'], tx['recipient'], tx['signature'], tx['amount']) for tx in
block['transactions']]
updated_block = Block(block['index'], block['previous_hash'], transactions, block['proof'],
block['timestamp'])
updated_blockchain.append(updated_block)
self.__chain = updated_blockchain
open_transactions = loads(file_content[1][:-1])
updated_open_transactions = []
for tx in open_transactions:
updated_transaction = Transaction(tx['sender'], tx['recipient'], tx['signature'], tx['amount'])
updated_open_transactions.append(updated_transaction)
self.__open_transactions = updated_open_transactions
self.__peer_nodes = set(loads(file_content[2]))
except (IOError, IndexError):
print('File not found!')
def save_data(self):
with open('blockchain-{}.p'.format(self.node_id), mode='wb') as file:
data = {
'chain': self.__chain,
'ot': self.__open_transactions
}
file.write(pickle.dumps(data))
with open('blockchain-{}.txt'.format(self.node_id), mode='w') as file:
savable_chain = [
block.__dict__ for block in [
Block(block_el.index, block_el.previous_hash, [
tx.__dict__ for tx in block_el.transactions
], block_el.proof, block_el.timestamp) for block_el in self.__chain
]
]
file.write(dumps(savable_chain))
file.write('\n')
savable_open_transactions = [tx.__dict__ for tx in self.__open_transactions]
file.write(dumps(savable_open_transactions))
file.write('\n')
file.write(dumps(list(self.__peer_nodes)))
def proof_of_work(self):
last_block = self.__chain[-1]
last_hash = hash_block(last_block)
proof = 0
while not Verification.valid_proof(self.__open_transactions, last_hash, proof):
proof += 1
return proof
def get_balance(self, sender=None):
""" Calculates the balance for a blockchain participant.
:return: The current balance for the participant.
"""
if sender is None:
if self.public_key is None:
return None
participant = self.public_key
else:
participant = sender
user_transactions = [[tx.amount * -1 for tx in block.transactions if tx.sender == participant] for block in self.__chain]
user_transactions.extend(
[[tx.amount for tx in block.transactions if tx.recipient == participant] for block in self.__chain])
user_transactions.append([tx.amount * -1 for tx in self.__open_transactions if tx.sender == participant])
return reduce(lambda tx_sum, tx_amt: tx_sum + sum(tx_amt) if len(tx_amt) > 0 else tx_sum, user_transactions, 0)
def get_last_blockchain_value(self):
""" Returns the last value of the current blockchain. """
return None if not self.__chain else self.__chain[-1]
def add_transaction(self, recipient, sender, signature, amount=1.0, is_receiving=False):
""" Append a new value as well as the last blockchain value to the blockchain.
Arguments:
sender: The sender of the coins.
recipient: The recipient of the coins.
signature: The signature of the payload, constructed via a private key.
amount: The amount of coins sent with the transaction (default = 1.0).
is_receiving: A boolean to determine whether or not this is an incoming request from another node.
"""
# if self.public_key is None:
# return False
transaction = Transaction(sender, recipient, signature, amount)
if Verification.verify_transaction(transaction, self.get_balance):
self.__open_transactions.append(transaction)
self.save_data()
if not is_receiving:
for node in self.__peer_nodes:
url = 'http://{}/broadcast_transaction'.format(node)
try:
response = requests.post(url, json={'sender': sender, 'recipient': recipient, 'amount': amount, 'signature': signature})
if response.status_code == 400 or response.status_code == 500:
print('Transaction declined, needs resolving.')
return False
except requests.exceptions.ConnectionError:
continue
return True
else:
return False
def mine_block(self):
if self.public_key is None:
return None
hashed_block = hash_block(self.__chain[-1])
proof = self.proof_of_work()
reward_transaction = Transaction(Blockchain.MINING_REWARD_SENDER, self.public_key, '', Blockchain.MINING_REWARD)
copied_transactions = self.__open_transactions[:]
for tx in copied_transactions:
if not Wallet.verify_transaction(tx):
return None
copied_transactions.append(reward_transaction)
block = Block(len(self.__chain), hashed_block, copied_transactions, proof)
self.__chain.append(block)
self.__open_transactions = []
self.save_data()
for node in self.__peer_nodes:
url = 'http://{}/broadcast-block'.format(node)
converted_block = block.__dict__.copy()
converted_block['transactions'] = [tx.__dict__ for tx in converted_block['transactions']]
try:
response = requests.post(url, json={'block': converted_block})
if response.status_code == 400 or response.status_code == 500:
print('Block declined, needs resolving.')
if response.status_code == 409:
self.resolve_conflicts = True
except requests.exceptions.ConnectionError:
continue
return block
def add_block(self, block):
transactions = [Transaction(tx['sender'], tx['recipient'], tx['signature'], tx['amount']) for tx in block['transactions']]
# Excluding the last transaction, because that is the "reward" transaction
valid_proof = Verification.valid_proof(transactions[:-1], block['previous_hash'], block['proof'])
hashes_match = hash_block(self.chain[-1]) == block['previous_hash']
if not valid_proof or not hashes_match:
return False
converted_block = Block(block['index'], block['previous_hash'], transactions, block['proof'], block['timestamp'])
self.__chain.append(converted_block)
stored_transactions = self.__open_transactions[:]
for itx in block['transactions']:
for opentx in stored_transactions:
if opentx.sender == itx['sender'] and opentx.recipient == itx['recipient'] and opentx.amount == itx['amount'] and opentx.signature == itx['signature']:
try:
self.__open_transactions.remove(opentx)
except ValueError:
print('Item was already removed')
self.save_data()
return True
def resolve(self):
winner_chain = self.chain
replace = False
for node in self.__peer_nodes:
url = 'http://{}/chain'.format(node)
try:
response = requests.get(url)
node_chain = response.json()
node_chain = [Block(block['index'], block['previous_hash'], [Transaction(tx['sender'], tx['recipient'], tx['signature'], tx['amount']) for tx in block['transactions']], block['proof'], block['timestamp']) for block in node_chain]
node_chain_length = len(node_chain)
local_chain_length = len(self.chain)
if node_chain_length > local_chain_length and Verification.verify_chain(node_chain):
winner_chain = node_chain
replace = True
except requests.exceptions.ConnectionError:
continue
self.resolve_conflicts = False
self.__chain = winner_chain
if replace:
self.__open_transactions = []
self.save_data()
return replace
def add_peer_node(self, node):
""" Adds a new node to the peer node set.
Arguments:
node: The node URL which should be added.
"""
self.__peer_nodes.add(node)
self.save_data()
def remove_peer_node(self, node):
""" Removes a new node to the peer node set.
Arguments:
node: The node URL which should be removed.
"""
self.__peer_nodes.discard(node)
self.save_data()
def get_peer_nodes(self):
""" Return a list of all connected peer nodes. """
return list(self.__peer_nodes)