OOP Capstone Projects

# =========================================================================
# PROJECT 1: OBJECT-ORIENTED BANK MANAGEMENT SYSTEM
# =========================================================================

class BankAccount:
    interest_rate = 0.04  # 4% Annual Interest (Class Variable)

    def __init__(self, account_number, holder_name, initial_balance=0.0):
        self.account_number = account_number
        self.holder_name = holder_name
        self._balance = float(initial_balance)
        self.transaction_history = [f"Account opened with ₹{initial_balance:,.2f}"]

    @property
    def balance(self):
        return self._balance

    def deposit(self, amount):
        if amount <= 0:
            return "❌ Deposit amount must be positive!"
        self._balance += amount
        self.transaction_history.append(f"Deposited +₹{amount:,.2f}")
        return f"✅ Deposited ₹{amount:,.2f}. New Balance: ₹{self._balance:,.2f}"

    def withdraw(self, amount):
        if amount > self._balance:
            return f"❌ Insufficient funds! Available Balance: ₹{self._balance:,.2f}"
        self._balance -= amount
        self.transaction_history.append(f"Withdrew -₹{amount:,.2f}")
        return f"✅ Withdrew ₹{amount:,.2f}. Remaining Balance: ₹{self._balance:,.2f}"

    def apply_interest(self):
        interest_earned = self._balance * BankAccount.interest_rate
        self._balance += interest_earned
        self.transaction_history.append(f"Interest credited +₹{interest_earned:,.2f}")
        return f"📈 Interest of ₹{interest_earned:,.2f} credited at {BankAccount.interest_rate*100}%"

    def get_statement(self):
        header = f"=== 🏦 STATEMENT: {self.holder_name} (Acc #{self.account_number}) ==="
        body = "\n".join([f"  • {tx}" for tx in self.transaction_history])
        footer = f"Current Available Balance: ₹{self._balance:,.2f}\n" + "=" * 50
        return f"{header}\n{body}\n{footer}"

# Run Banking System Demo:
acc = BankAccount("SBI-9021", "Balaji", 10000.0)
print(acc.deposit(5000.0))
print(acc.withdraw(3000.0))
print(acc.apply_interest())
print("\n" + acc.get_statement())

# =========================================================================
# PROJECT 2: LIBRARY CATALOG & BOOK LENDING SYSTEM
# =========================================================================

class Book:
    def __init__(self, book_id, title, author):
        self.book_id = book_id
        self.title = title
        self.author = author
        self.is_borrowed = False
        self.borrowed_by = None

    def __str__(self):
        status = f"Borrowed by {self.borrowed_by}" if self.is_borrowed else "Available ✅"
        return f"[{self.book_id}] '{self.title}' by {self.author} ({status})"

class Library:
    def __init__(self, name):
        self.name = name
        self.catalog = {}  # book_id -> Book object

    def add_book(self, book):
        self.catalog[book.book_id] = book
        print(f"📚 Added to library: {book.title}")

    def lend_book(self, book_id, borrower_name):
        book = self.catalog.get(book_id)
        if not book:
            return "❌ Error: Book not found in catalog!"
        if book.is_borrowed:
            return f"❌ '{book.title}' is currently borrowed by {book.borrowed_by}!"
        book.is_borrowed = True
        book.borrowed_by = borrower_name
        return f"📖 Successfully issued '{book.title}' to {borrower_name}."

    def return_book(self, book_id):
        book = self.catalog.get(book_id)
        if not book or not book.is_borrowed:
            return "❌ Error: Book is not currently on loan!"
        borrower = book.borrowed_by
        book.is_borrowed = False
        book.borrowed_by = None
        return f"✅ '{book.title}' returned successfully by {borrower}."

    def display_catalog(self):
        print(f"\n--- 🏛️ {self.name} Catalog ---")
        for b in self.catalog.values():
            print("•", b)

# Run Library System Demo:
lib = Library("City Central Tech Library")
lib.add_book(Book("B101", "Fluent Python", "Luciano Ramalho"))
lib.add_book(Book("B102", "Clean Code", "Robert C. Martin"))
lib.add_book(Book("B103", "Designing Data-Intensive Apps", "Martin Kleppmann"))

lib.display_catalog()
print("\n" + lib.lend_book("B101", "Balaji"))
print(lib.lend_book("B101", "Alex")) # Test duplicate loan attempt
lib.display_catalog()
print("\n" + lib.return_book("B101"))

# =========================================================================
# PROJECT 3: ROLE-BASED EMPLOYEE PAYROLL SYSTEM
# =========================================================================
from abc import ABC, abstractmethod

class Employee(ABC):
    def __init__(self, emp_id, name, department):
        self.emp_id = emp_id
        self.name = name
        self.department = department

    @abstractmethod
    def calculate_pay(self):
        """Abstract method calculating monthly compensation."""
        pass

    def __str__(self):
        return f"[{self.emp_id}] {self.name:12} ({self.department:10}) | Monthly Pay: ₹{self.calculate_pay():,.2f}"

class SalariedEmployee(Employee):
    def __init__(self, emp_id, name, department, monthly_salary):
        super().__init__(emp_id, name, department)
        self.monthly_salary = monthly_salary

    def calculate_pay(self):
        return self.monthly_salary

class HourlyEmployee(Employee):
    def __init__(self, emp_id, name, department, hourly_rate, hours_worked):
        super().__init__(emp_id, name, department)
        self.hourly_rate = hourly_rate
        self.hours_worked = hours_worked

    def calculate_pay(self):
        return self.hourly_rate * self.hours_worked

class Manager(SalariedEmployee):
    def __init__(self, emp_id, name, department, monthly_salary, bonus):
        super().__init__(emp_id, name, department, monthly_salary)
        self.bonus = bonus

    def calculate_pay(self):
        return self.monthly_salary + self.bonus

# Payroll Processing Engine:
staff = [
    SalariedEmployee("E101", "Balaji", "Engineering", 120000),
    HourlyEmployee("E102", "Alex", "Design", 800, 160),
    Manager("M101", "Chloe", "Management", 150000, 35000)
]

print("--- 💼 Monthly Corporate Payroll Summary ---")
total_payroll = 0
for emp in staff:
    print(emp)
    total_payroll += emp.calculate_pay()
print("=" * 60)
print(f"💰 Total Company Payroll Outflow: ₹{total_payroll:,.2f}")

# =========================================================================
# PROJECT 4: E-COMMERCE SHOPPING CART SYSTEM
# =========================================================================

class Item:
    def __init__(self, item_id, name, unit_price):
        self.item_id = item_id
        self.name = name
        self.unit_price = float(unit_price)

class CartItem:
    def __init__(self, item, quantity=1):
        self.item = item
        self.quantity = quantity

    @property
    def subtotal(self):
        return self.item.unit_price * self.quantity

class ShoppingCart:
    def __init__(self, customer_name):
        self.customer_name = customer_name
        self.items = {}  # item_id -> CartItem

    def add_item(self, item, qty=1):
        if item.item_id in self.items:
            self.items[item.item_id].quantity += qty
        else:
            self.items[item.item_id] = CartItem(item, qty)
        print(f"🛒 Added {qty}x '{item.name}' to cart.")

    def calculate_total(self, discount_percent=0.0, tax_percent=0.18):
        gross = sum(ci.subtotal for ci in self.items.values())
        discount = gross * (discount_percent / 100)
        taxable = gross - discount
        tax = taxable * tax_percent
        final_bill = taxable + tax
        return gross, discount, tax, final_bill

    def print_invoice(self, coupon_discount=10):
        gross, disc, tax, net = self.calculate_total(coupon_discount)
        print("\n" + "=" * 48)
        print(f"🛍️ INVOICE: {self.customer_name}'s Cart")
        print("=" * 48)
        for ci in self.items.values():
            print(f"• {ci.item.name:20} x{ci.quantity} @ ₹{ci.item.unit_price:,.2f} = ₹{ci.subtotal:,.2f}")
        print("-" * 48)
        print(f"Gross Subtotal:     ₹{gross:,.2f}")
        print(f"Coupon ({coupon_discount}% off):  -₹{disc:,.2f}")
        print(f"GST Tax (18%):      +₹{tax:,.2f}")
        print(f"TOTAL PAYABLE:      ₹{net:,.2f}")
        print("=" * 48)

# Run Shopping Cart Demo:
laptop = Item("ITM01", "Dell XPS 15", 145000)
mouse = Item("ITM02", "Logitech MX Master", 8500)

cart = ShoppingCart("Balaji")
cart.add_item(laptop, 1)
cart.add_item(mouse, 2)
cart.print_invoice(coupon_discount=10)

# =========================================================================
# PROJECT 5: SCHOOL MANAGEMENT SYSTEM
# =========================================================================

class Person:
    def __init__(self, person_id, name, email):
        self.person_id = person_id
        self.name = name
        self.email = email

class Teacher(Person):
    def __init__(self, person_id, name, email, subject):
        super().__init__(person_id, name, email)
        self.subject = subject

    def __str__(self):
        return f"👨‍🏫 Prof. {self.name} (Subject: {self.subject})"

class Course:
    def __init__(self, course_code, title, teacher):
        self.course_code = course_code
        self.title = title
        self.teacher = teacher
        self.enrolled_students = []

    def enroll(self, student):
        if student not in self.enrolled_students:
            self.enrolled_students.append(student)
            student.courses.append(self)

class Student(Person):
    def __init__(self, person_id, name, email, grade_level):
        super().__init__(person_id, name, email)
        self.grade_level = grade_level
        self.courses = []
        self.grades = {}  # course_code -> mark

    def assign_grade(self, course_code, mark):
        self.grades[course_code] = mark

    def get_report_card(self):
        lines = [f"🎓 ACADEMIC REPORT: {self.name} (Grade: {self.grade_level})"]
        for c in self.courses:
            score = self.grades.get(c.course_code, "In Progress")
            lines.append(f"  • {c.title:25} (Instructor: {c.teacher.name}) -> Score: {score}")
        return "\n".join(lines)

# Run School System Demo:
prof_sharma = Teacher("T01", "Dr. Sharma", "sharma@school.edu", "Python & Algorithms")
prof_rao = Teacher("T02", "Dr. Rao", "rao@school.edu", "Computer Networks")

py_course = Course("CS101", "Advanced Python 3", prof_sharma)
net_course = Course("CS102", "Computer Networks", prof_rao)

student1 = Student("S101", "Balaji", "balaji@school.edu", "12th Standard")
py_course.enroll(student1)
net_course.enroll(student1)

student1.assign_grade("CS101", 96)
student1.assign_grade("CS102", 91)

print(student1.get_report_card())