class Blockchain:
def __init__(self):
self.csv_operator = CSV()
def get_hash(self, block):
encoded_block = json.dumps(block, sort_keys=True).encode()
return hashlib.sha256(encoded_block).hexdigest()
def proof_of_work(self, previous_nonce):
new_nonce = 1
check_nonce = True
while check_nonce:
hash_operation = hashlib.sha256(
str(new_nonce**2 - previous_nonce**2).encode()).hexdigest()
if hash_operation[:4] == '0000':
check_nonce = False
else:
new_nonce += 1
return new_nonce
def chain_is_valid(self):
for previous_block, current_block in self.csv_operator.read_chain():
if self.get_hash(previous_block) != current_block["hash"]["block"]:
return False
hash_operation = hashlib.sha256(
str(current_block["nonce"]**2 -
previous_block["nonce"]**2).encode()).hexdigest()
if hash_operation[:4] != '0000':
return False
return True
def add_genesis_block(self):
block = {
"_id": 0,
"car_id": "None",
"nonce": 0,
"hash": {
"block": "None",
"car": "None"
},
"details": {
"block_type": "None"
}
}
self.chain.append(block)
def mine_block(self, block_type, block_data):
client = DBConnect()
last_block = self.csv_operator.get_last_block()
_id = self.csv_operator.get_chain_length()
car_id = block_data[0]
nonce = self.proof_of_work(last_block["nonce"])
last_hash_block = self.get_hash(last_block)
last_hash_car = "None"
if block_type == "Production":
block = {
"_id": _id,
"car_id": car_id,
"nonce": nonce,
"hash": {
"block": last_hash_block,
"car": last_hash_car
},
"details": {
"block_type": "Production"
}
}
elif block_type == "NewRegister":
block = {
"_id": _id,
"car_id": car_id,
"nonce": nonce,
"hash": {
"block": last_hash_block,
"car": last_hash_car
},
"details": {
"block_type": "NewRegister"
}
}
elif block_type == "Repair":
last_car_entry = client.get_car_history(car_id)[-1]
last_hash_car = self.get_hash(last_car_entry)
block = {
"_id": _id,
"car_id": car_id,
"nonce": nonce,
"hash": {
"block": last_hash_block,
"car": last_hash_car
},
"details": {
"block_type": "Repair",
}
}
elif block_type == "Sale":
last_car_entry = client.get_car_history(car_id)[-1]
last_hash_car = self.get_hash(last_car_entry)
block = {
"_id": _id,
"car_id": car_id,
"nonce": nonce,
"hash": {
"block": last_hash_block,
"car": last_hash_car
},
"details": {
"block_type": "Sale"
}
}
else:
return "wrong input"
client.ingest_block(block)
self.csv_operator.add_block(block)
def car_history_is_valid(self, car_id):
"""
car history is valid if
1. chain is valid
2. entries in data base match corresponding chain entries
3. the hashes that link the car history are valid
"""
if self.chain_is_valid():
client = DBConnect()
car_history = client.get_car_history(car_id)
for stage in car_history:
if stage != self.chain[stage["_id"]]:
return False
if len(car_history) <= 1:
return True
index = 1
while index < len(car_history):
if self.get_hash(
car_history[index -
1]) != car_history[index]["hash"]["car"]:
return False
index += 1
return True
else:
return False
def replace_chain(self):
longest_chain = None
max_length = len(self.chain)
for node in self.nodes:
response = requests.get(f'http://{node}/get_chain')
if response.status_code == 200:
length = response.json()['length']
chain = response.json()['chain']
if length > max_length and self.is_chain_valid(chain):
max_length = length
longest_chain = chain
if longest_chain:
self.chain = longest_chain
return True
return False
