// Exercise 1: virtual dispatch vs method hiding
//
// Implement the Shape hierarchy so that:
//   - Shape.Describe() is NOT overridden anywhere, but calling it through
//     any subtype must report the CORRECT overridden Area() (polymorphism).
//   - Square.Area() properly overrides Shape.Area() using `virtual`/`override`.
//   - Triangle.Area() uses `new` to HIDE Shape.Area() instead of overriding it
//     (this is deliberately here to demonstrate the difference in the self-check).

using System;

class Shape
{
    public virtual double Area() => 0;
    public string Describe() => $"Area = {Area()}";
}

class Square : Shape
{
    public double Side { get; init; }
    // TODO: override Area() to return Side * Side
}

class Triangle : Shape
{
    public double Base { get; init; }
    public double Height { get; init; }
    // TODO: use `new` (member hiding, NOT override) to define Area() as
    // 0.5 * Base * Height. This intentionally breaks polymorphism —
    // the self-check demonstrates why.
}

class Program
{
    static void Main()
    {
        int pass = 0, total = 0;

        Shape sq = new Square { Side = 4 };
        total++;
        if (sq.Describe() == "Area = 16") { Console.WriteLine("PASS: Square overrides correctly"); pass++; }
        else Console.WriteLine("FAIL: Square overrides correctly, got " + sq.Describe());

        // Triangle.Area() hides rather than overrides, so calling through
        // a Shape-typed reference should still hit Shape.Area() (= 0),
        // even though Triangle "has its own" Area().
        Shape tri = new Triangle { Base = 6, Height = 2 };
        total++;
        if (tri.Describe() == "Area = 0") { Console.WriteLine("PASS: Triangle's `new` hides, base reference sees Shape.Area()"); pass++; }
        else Console.WriteLine("FAIL: Triangle's `new` hides, base reference sees Shape.Area(), got " + tri.Describe());

        // But calling Area() through the CONCRETE Triangle type should see
        // Triangle's own hidden method.
        var triConcrete = new Triangle { Base = 6, Height = 2 };
        total++;
        if (triConcrete.Area() == 6) { Console.WriteLine("PASS: concrete Triangle reference sees Triangle.Area()"); pass++; }
        else Console.WriteLine("FAIL: concrete Triangle reference sees Triangle.Area(), got " + triConcrete.Area());

        Console.WriteLine($"--- {pass}/{total} checks passed ---");
    }
}