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

namespace Kyoo.Abstractions.Models
{
	/// <summary>
	/// A page of resource that contains information about the pagination of resources.
	/// </summary>
	/// <typeparam name="T">The type of resource contained in this page.</typeparam>
	public class Page<T> where T : IResource
	{
		/// <summary>
		/// The link of the current page.
		/// </summary>
		public string This { get; }
		
		/// <summary>
		/// The link of the first page.
		/// </summary>
		public string First { get; }
		
		/// <summary>
		/// The link of the next page.
		/// </summary>
		public string Next { get; }

		/// <summary>
		/// The number of items in the current page.
		/// </summary>
		public int Count => Items.Count;
		
		/// <summary>
		/// The list of items in the page.
		/// </summary>
		public ICollection<T> Items { get; }
		
		
		/// <summary>
		/// Create a new <see cref="Page{T}"/>.
		/// </summary>
		/// <param name="items">The list of items in the page.</param>
		/// <param name="this">The link of the current page.</param>
		/// <param name="next">The link of the next page.</param>
		/// <param name="first">The link of the first page.</param>
		public Page(ICollection<T> items, string @this, string next, string first)
		{
			Items = items;
			This = @this;
			Next = next;
			First = first;
		}

		/// <summary>
		/// Create a new <see cref="Page{T}"/> and compute the urls.
		/// </summary>
		/// <param name="items">The list of items in the page.</param>
		/// <param name="url">The base url of the resources available from this page.</param>
		/// <param name="query">The list of query strings of the current page</param>
		/// <param name="limit">The number of items requested for the current page.</param>
		public Page(ICollection<T> items,
			string url,
			Dictionary<string, string> query,
			int limit)
		{
			Items = items;
			This = url + query.ToQueryString();

			if (items.Count == limit && limit > 0)
			{
				query["afterID"] = items.Last().ID.ToString();
				Next = url + query.ToQueryString();
			}
			
			query.Remove("afterID");
			First = url + query.ToQueryString();
		}
	}
}