Untitled

using System;

namespace OOPConceptsDemo
{
    // ================================
    // 🔹 ABSTRACTION
    // ================================
    // Abstract class only defines general structure (no detailed implementation)
    public abstract class VehicleBase
    {
        public string Brand { get; set; }

        public abstract void StartEngine();
        public abstract void StopEngine();
    }

    // ================================
    // 🔹 ENCAPSULATION
    // ================================
    // Data (fields) are hidden using private + accessed through public methods/properties
    public class Vehicle : VehicleBase
    {
        private int speed; // private → cannot be accessed directly from outside

        // Public property to get/set speed safely
        public int Speed
        {
            get { return speed; }
            set
            {
                if (value >= 0)
                    speed = value;
                else
                    Console.WriteLine("Speed cannot be negative!");
            }
        }

        // Implement abstract methods (Abstraction)
        public override void StartEngine()
        {
            Console.WriteLine($"{Brand} engine started.");
        }

        public override void StopEngine()
        {
            Console.WriteLine($"{Brand} engine stopped.");
        }

        // Encapsulated behavior: only this method can change speed
        public void Accelerate(int increase)
        {
            speed += increase;
            Console.WriteLine($"{Brand} speed is now {speed} km/h");
        }
    }

    // ================================
    // 🔹 INHERITANCE
    // ================================
    // Child classes inherit properties/methods from Vehicle
    public class Car : Vehicle
    {
        public int Doors { get; set; }

        public void OpenDoor()
        {
            Console.WriteLine($"{Brand} opens {Doors} doors.");
        }
    }

    public class Motorcycle : Vehicle
    {
        public bool HasSidecar { get; set; }

        public void ShowType()
        {
            if (HasSidecar)
                Console.WriteLine($"{Brand} is a sidecar motorcycle.");
            else
                Console.WriteLine($"{Brand} is a regular motorcycle.");
        }
    }

    // ================================
    // 🔹 POLYMORPHISM
    // ================================
    // Same method name → different behaviors depending on the object
    public class VehiclePoly
    {
        public virtual void Honk()
        {
            Console.WriteLine("Generic vehicle sound 🚗");
        }
    }

    public class CarPoly : VehiclePoly
    {
        public override void Honk()
        {
            Console.WriteLine("Car honks: Beep Beep!");
        }
    }

    public class MotorcyclePoly : VehiclePoly
    {
        public override void Honk()
        {
            Console.WriteLine("Motorcycle honks: Beeeem!");
        }
    }

    // ================================
    // 🔹 MAIN PROGRAM
    // ================================
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("=== OOP Concepts Demo in C# ===\n");

            // --- Abstraction + Encapsulation ---
            Vehicle myCar = new Vehicle();
            myCar.Brand = "Toyota";
            myCar.StartEngine();
            myCar.Accelerate(50);
            myCar.StopEngine();
            Console.WriteLine();

            // --- Inheritance ---
            Car car = new Car { Brand = "Honda", Doors = 4 };
            car.StartEngine();
            car.OpenDoor();
            car.Accelerate(60);
            car.StopEngine();
            Console.WriteLine();

            Motorcycle motor = new Motorcycle { Brand = "Yamaha", HasSidecar = false };
            motor.StartEngine();
            motor.ShowType();
            motor.Accelerate(80);
            motor.StopEngine();
            Console.WriteLine();

            // --- Polymorphism ---
            VehiclePoly[] vehicles = { new CarPoly(), new MotorcyclePoly() };
            foreach (var v in vehicles)
            {
                v.Honk();  // Same method, different output depending on type
            }

            Console.WriteLine("\n=== End of Program ===");
        }
    }
}