Bank.py

# Bank.py
import json
import os
import random
import hashlib

class BankLogic:
    def __init__(self, db_file="bank_users.json"):
        self.db_file = db_file
        self.users = {}
        self.current_user = None
        self.load_users()

    # ---------------- File Handling ----------------
    def load_users(self):
        """Load users from JSON file (persistent storage)."""
        if os.path.exists(self.db_file):
            try:
                with open(self.db_file, "r") as f:
                    self.users = json.load(f)
            except (json.JSONDecodeError, IOError):
                # Backup corrupted file
                try:
                    os.rename(self.db_file, self.db_file + ".corrupt")
                except Exception:
                    pass
                self.users = {}
        else:
            self.users = {}

    def save_users(self):
        """Save users to JSON file (persistent storage)."""
        try:
            with open(self.db_file, "w") as f:
                json.dump(self.users, f, indent=4)
        except Exception as e:
            return False, f"Failed to save users: {str(e)}"
        return True, "Saved successfully"

    # ---------------- Account Handling ----------------
    def _generate_account_number(self):
        """Generate a unique 8-digit account number starting with 0010."""
        while True:
            acc_no = "0010" + str(random.randint(1000, 9999))
            if acc_no not in self.users:
                return acc_no

    def _hash_pin(self, pin):
        return hashlib.sha256(pin.encode()).hexdigest()

    def create_account(self, name, age, pin):
        """Create a new account and return its number and user data."""
        if not pin.isdigit() or len(pin) != 4:
            return False, "PIN must be a 4-digit number.", None, None
        try:
            age = int(age)
        except ValueError:
            return False, "Age must be an integer.", None, None
        if age < 18:
            return False, "Age must be 18 or older.", None, None

        account_no = self._generate_account_number()
        hashed_pin = self._hash_pin(pin)
        self.users[account_no] = {
            "account_no": account_no,
            "name": name,
            "age": age,
            "pin": hashed_pin,
            "balance": 0.0,
            "transactions": []
        }
        self.save_users()
        return True, "Account created successfully.", account_no, self.users[account_no]

    def login(self, account_no, pin):
        """Login with account number and PIN."""
        hashed_input = self._hash_pin(pin)
        user = self.users.get(account_no)
        if user and user["pin"] == hashed_input:
            self.current_user = account_no
            return True, "Login successful.", user
        else:
            return False, "Invalid account number or PIN.", None

    def logout(self):
        """Logout current user."""
        self.current_user = None

    # ---------------- Banking Operations ----------------
    def deposit(self, amount):
        """Deposit amount, update balance, return result."""
        if not self.current_user:
            return False, "No user logged in.", None
        if amount is None or amount <= 0:
            return False, "Invalid deposit amount.", None
        self.users[self.current_user]["balance"] += amount
        entry = f"Deposited: {amount:.2f}"
        self.users[self.current_user]["transactions"].append(entry)
        self.save_users()
        return True, entry, self.users[self.current_user]["balance"]

    def withdraw(self, amount):
        """Withdraw amount, update balance, return result."""
        if not self.current_user:
            return False, "No user logged in.", None
        if amount is None or amount <= 0:
            return False, "Invalid withdrawal amount.", None
        if self.users[self.current_user]["balance"] < amount:
            return False, "Insufficient balance.", None
        self.users[self.current_user]["balance"] -= amount
        entry = f"Withdrawn: {amount:.2f}"
        self.users[self.current_user]["transactions"].append(entry)
        self.save_users()
        return True, entry, self.users[self.current_user]["balance"]

    def get_transaction_log(self):
        """Return transactions for the current user."""
        if not self.current_user:
            return False, "No user logged in.", []
        transactions = self.users[self.current_user]["transactions"]
        return True, "Log retrieved.", transactions