using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Composite
{
    /// <summary>

    /// MainApp startup class for Structural 

    /// Composite Design Pattern.

    /// </summary>

    class MainApp
    {
        /// <summary>

        /// Entry point into console application.

        /// </summary>

        static void Main()
        {
            // Create a tree structure

            Composite root = new Composite("root");
            root.Add(new Leaf("Leaf A"));
            root.Add(new Leaf("Leaf B"));

            Composite comp = new Composite("Composite X");
            comp.Add(new Leaf("Leaf XA"));
            comp.Add(new Leaf("Leaf XB"));

            root.Add(comp);
            root.Add(new Leaf("Leaf C"));

            // Add and remove a leaf

            Leaf leaf = new Leaf("Leaf D");
            root.Add(leaf);
            root.Remove(leaf);

            // Recursively display tree

            root.Display(1);

            // Wait for user

            Console.ReadKey();
        }
    }

    /// <summary>

    /// The 'Component' abstract class

    /// </summary>

    abstract class Component
    {
        protected string name;

        // Constructor

        public Component(string name)
        {
            this.name = name;
        }

        public abstract void Add(Component c);
        public abstract void Remove(Component c);
        public abstract void Display(int depth);
    }

    /// <summary>

    /// The 'Composite' class

    /// </summary>

    class Composite : Component
    {
        private List<Component> _children = new List<Component>();

        // Constructor

        public Composite(string name)
            : base(name)
        {
        }

        public override void Add(Component component)
        {
            _children.Add(component);
        }

        public override void Remove(Component component)
        {
            _children.Remove(component);
        }

        public override void Display(int depth)
        {
            Console.WriteLine(new String('-', depth) + name);

            // Recursively display child nodes

            foreach (Component component in _children)
            {
                component.Display(depth + 2);
            }
        }
    }

    /// <summary>

    /// The 'Leaf' class

    /// </summary>

    class Leaf : Component
    {
        // Constructor

        public Leaf(string name)
            : base(name)
        {
        }

        public override void Add(Component c)
        {
            Console.WriteLine("Cannot add to a leaf");
        }

        public override void Remove(Component c)
        {
            Console.WriteLine("Cannot remove from a leaf");
        }

        public override void Display(int depth)
        {
            Console.WriteLine(new String('-', depth) + name);
        }
    }
}