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

namespace LinkedList
{
    class List
    {
        private Link _head;
        private Link _tail;

        public List()
        {
            _head = new Link(null);
            _tail = _head;
        }

        public void Append(Product product)
        {
            Link link = new Link(product);
            _tail.Append(link);
            _tail = link;
        }

        public void Insert(Product product)
        {
            if (_head.Next != null) Insert(_head.Next, product);
            else Append(product);
        }

        public void Insert(Link link, Product product)
        {
            link.Insert(new Link(product));
        }

        public void Remove(Product product)
        {
            Link found = Find(product);
            if(found != null)
            {
                if (found == _tail) _tail = found.Prev;
                found.Unlink();
            }
        }

        public Link Find(Product product)
        {
            Link next = _head.Next;
            while(next != null)
            {
                if (next.Product == product) return next;
                next = next.Next;
            }
            return null;
        }

        public void Display()
        {
            Link next = _head.Next;
            int i = 0;

            if (next == null) { Console.WriteLine("Empty list"); return; }

            while (next != null)
            {
                Console.WriteLine("{0}: {1}", i++, next.Product.Name);
                next = next.Next;
            }
        }
    }
}