using System;
using System.Collections.Generic;

namespace DotNetDesignPatternDemos.SOLID.OCP
{
    public enum Color
    { Red, Green, Blue }

    public enum Size
    { Small, Medium, Large }

    public class Product
    {
        public string Name;
        public Color Color;
        public Size Size;

        public Product(string name, Color color, Size size)
        {
            Name = name ?? throw new ArgumentNullException(paramName: nameof(name));
            Color = color;
            Size = size;
        }
    }

    //so Filter can take different specifications(constraints)
    public interface IProductSpecification
    {
        bool IsSatisfied(Product i);
    }

    public class ItemFilter
    {
        public IEnumerable<Product> Filter(IEnumerable<Product> items, IProductSpecification spec)
        {
            foreach (Product item in items)
            {
                if (spec.IsSatisfied(item))
                {
                    yield return item;
                }
            }
        }
    }

    public class ColorSpecification : IProductSpecification
    {
        private Color color;
        public ColorSpecification(Color color)
        {
            this.color = color;
        }

        public bool IsSatisfied(Product p)
        {
            return this.color == p.Color;
        }
    }


    public class Demo
    {
        static void Main()
        {
            var apple = new Product("Apple", Color.Green, Size.Small);
            var tree = new Product("Tree", Color.Green, Size.Large);
            var house = new Product("House", Color.Blue, Size.Large);

            Product[] products = { apple, tree, house };
            ItemFilter PF = new ItemFilter();
            ColorSpecification GreenOnly = new ColorSpecification(Color.Green);

            foreach (Product p in PF.Filter(products, GreenOnly))
            {
                Console.WriteLine(p.Name);
            }
            Console.ReadKey();
        }
    }
}