using System;
using System.Collections;
using System.Collections.Generic;

namespace D21._1
{
    public class Inventory : IEnumerable<Item>
    {
        public Item Item;
        public Inventory NextEntry;

        public int Count<T>() where T : Item => (NextEntry?.Count<T>() ?? 0) + (Item is T ? 1 : 0);
        public override int GetHashCode() => HashCode.Combine(Item, NextEntry);
        public bool Contains(Item i)
        {
            var cur = this;
            while (cur != null)
            {
                if (i.Equals(cur.Item)) return true;
                cur = cur.NextEntry;
            }
            return false;
        }

        public IEnumerator<Item> GetEnumerator()
        {
            var cur = this;
            while (cur != null)
            {
                yield return cur.Item;
                cur = cur.NextEntry;
            }
        }

        IEnumerator IEnumerable.GetEnumerator() => throw new NotImplementedException();
    }

    public abstract class Item
    {
        public string Name { get; set; }
        public int Damage { get; set; }
        public int Armor { get; set; }

        public override bool Equals(object obj) => obj is Item item && Name.Equals(item.Name, StringComparison.OrdinalIgnoreCase);

        public override int GetHashCode() => HashCode.Combine(Name);
    }

    public class Weapon : Item { }
    public class Armor : Item { }
    public class Ring : Item { }
}