Restore frontend (backend interlude) functionality

Author: 15Dkatz

backend/app/__init__.py

@@ -3,6 +3,7 @@
 import random
 
 from flask import Flask, jsonify, request
+from flask_cors import CORS
 
 from backend.blockchain.blockchain import Blockchain
 from backend.wallet.wallet import Wallet
@@ -11,8 +12,9 @@
 from backend.pubsub import PubSub
 
 app = Flask(__name__)
+CORS(app, resources={ r'/*': { 'origins': 'http://localhost:3000' } })
 blockchain = Blockchain()
-wallet = Wallet()
+wallet = Wallet(blockchain)
 transaction_pool = TransactionPool()
 pubsub = PubSub(blockchain, transaction_pool)
 
@@ -24,9 +26,23 @@ def route_default():
 def route_blockchain():
     return jsonify(blockchain.to_json())
 
+@app.route('/blockchain/range')
+def route_blockchain_range():
+    # http://localhost:5050/blockchain/range?start=2&end=5
+    start = int(request.args.get('start'))
+    end = int(request.args.get('end'))
+
+    return jsonify(blockchain.to_json()[::-1][start:end])
+
+@app.route('/blockchain/length')
+def route_blockchain_length():
+    return jsonify(len(blockchain.chain))
+
 @app.route('/blockchain/mine')
 def route_blockchain_mine():
-    blockchain.add_block(transaction_pool.transaction_data())
+    transaction_data = transaction_pool.transaction_data()
+    transaction_data.append(Transaction.reward_transaction(wallet).to_json())
+    blockchain.add_block(transaction_data)
     block = blockchain.chain[-1]
     pubsub.broadcast_block(block)
     transaction_pool.clear_blockchain_transactions(blockchain)
@@ -52,9 +68,28 @@ def route_wallet_transact():
         )
 
     pubsub.broadcast_transaction(transaction)
+    transaction_pool.set_transaction(transaction)
 
     return jsonify(transaction.to_json())
 
+@app.route('/wallet/info')
+def route_wallet_info():
+    return jsonify({ 'address': wallet.address, 'balance': wallet.balance })
+
+@app.route('/known-addresses')
+def route_known_addresses():
+    known_addresses = set()
+
+    for block in blockchain.chain:
+        for transaction in block.data:
+            known_addresses.update(transaction['output'].keys())
+
+    return jsonify(list(known_addresses))
+
+@app.route('/transactions')
+def route_transactions():
+    return jsonify(transaction_pool.transaction_data())
+
 ROOT_PORT = 5050
 PORT = ROOT_PORT
 
@@ -70,5 +105,17 @@ def route_wallet_transact():
     except Exception as e:
         print(f'\n -- Error synchronizing: {e}')
 
-app.run(port=5050)
+if os.environ.get('SEED_DATA') == 'True':
+    for i in range(10):
+        blockchain.add_block([
+            Transaction(Wallet(), Wallet().address, random.randint(2, 50)).to_json(),
+            Transaction(Wallet(), Wallet().address, random.randint(2, 50)).to_json()
+        ])
+
+    for i in range(3):
+        transaction_pool.set_transaction(
+            Transaction(Wallet(), Wallet().address, random.randint(2, 50))
+        )
+
+app.run(port=PORT)
 

backend/config.py

@@ -6,3 +6,6 @@
 MINE_RATE = 4 * SECONDS
 
 STARTING_BALANCE = 1000
+
+MINING_REWARD = 50
+MINING_REWARD_INPUT = { 'address': '*--official-mining-reward--*' }

backend/wallet/transaction.py

@@ -2,6 +2,7 @@
 import uuid
 
 from backend.wallet.wallet import Wallet
+from backend.config import MINING_REWARD, MINING_REWARD_INPUT
 
 class Transaction:
     """
@@ -88,6 +89,11 @@ def is_valid_transaction(transaction):
         Validate a transaction.
         Raise an exception for invalid transactions.
         """
+        if transaction.input == MINING_REWARD_INPUT:
+            if list(transaction.output.values()) != [MINING_REWARD]:
+                raise Exception('Invalid mining reward')
+            return
+
         output_total = sum(transaction.output.values())
 
         if transaction.input['amount'] != output_total:
@@ -100,6 +106,16 @@ def is_valid_transaction(transaction):
         ):
             raise Exception('Invalid signature')
 
+    @staticmethod
+    def reward_transaction(miner_wallet):
+        """
+        Generate a reward transaction that award the miner.
+        """
+        output = {}
+        output[miner_wallet.address] = MINING_REWARD
+
+        return Transaction(input=MINING_REWARD_INPUT, output=output)
+
 def main():
     transaction = Transaction(Wallet(), 'recipient', 15)
     print(f'transaction.__dict__: {transaction.__dict__}')

backend/wallet/wallet.py

@@ -17,16 +17,20 @@ class Wallet:
     Keeps track of the miner's balance.
     Allows a miner to authorize transactions.
     """
-    def __init__(self):
+    def __init__(self, blockchain=None):
+        self.blockchain = blockchain
         self.address = str(uuid.uuid4())[0:8]
-        self.balance = STARTING_BALANCE
         self.private_key = ec.generate_private_key(
             ec.SECP256K1(),
             default_backend()
         )
         self.public_key = self.private_key.public_key()
         self.serialize_public_key()
 
+    @property
+    def balance(self):
+        return Wallet.calculate_balance(self.blockchain, self.address)
+
     def sign(self, data):
         """
         Generate a signature based on the data using the local private key.
@@ -68,6 +72,31 @@ def verify(public_key, data, signature):
         except InvalidSignature:
             return False
 
+    @staticmethod
+    def calculate_balance(blockchain, address):
+        """
+        Calculate the balance of the given address considering the transaction
+        data within the blockchain.
+
+        The balance is found by adding the output values that belong to the
+        address since the most recent transaction by that address.
+        """
+        balance = STARTING_BALANCE
+
+        if not blockchain:
+            return balance
+
+        for block in blockchain.chain:
+            for transaction in block.data:
+                if transaction['input']['address'] == address:
+                    # Any time the address conducts a new transaction it resets
+                    # its balance
+                    balance = transaction['output'][address]
+                elif address in transaction['output']:
+                    balance += transaction['output'][address]
+
+        return balance
+
 def main():
     wallet = Wallet()
     print(f'wallet.__dict__: {wallet.__dict__}')

requirements.txt

@@ -1,4 +1,6 @@
 pytest==8.4.2
 Flask==3.1.2
+Flask-Cors==3.0.8
 pubnub==10.4.1
 requests==2.32.5
+cryptography==46.0.3