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

namespace Dpz.Core.Web.Pager;

/// <summary>
/// 表示包含分页数据对象的强类型列表。
/// </summary>
/// <typeparam name="T"></typeparam>
[MessagePackObject(keyAsPropertyName: true)]
public class PagedList<T> : List<T>, IPagedList<T>
{
    /// <summary>
    /// 使用要分页的所有数据项、当前页索引和每页显示的记录数初始化PagedList对象
    /// </summary>
    /// <param name="allItems">要分页的所有数据项</param>
    /// <param name="pageIndex">当前页索引</param>
    /// <param name="pageSize">每页显示的记录数</param>
    public PagedList(IEnumerable<T> allItems, int pageIndex, int pageSize)
    {
        PageSize = pageSize;
        var items = allItems as IList<T> ?? allItems.ToList();
        TotalItemCount = items.Count();
        CurrentPageIndex = pageIndex;
        AddRange(items.Skip(StartItemIndex - 1).Take(pageSize));
    }

    /// <summary>
    /// 使用当前页数据项、当前页索引、每页显示的记录数和要分页的总记录数初始化PagedList对象
    /// </summary>
    /// <param name="currentPageItems">当前页数据项</param>
    /// <param name="pageIndex">当前页索引</param>
    /// <param name="pageSize">每页显示的记录数</param>
    /// <param name="totalItemCount">要分页数据的总记录数</param>
    public PagedList(
        IEnumerable<T> currentPageItems,
        int pageIndex,
        int pageSize,
        int totalItemCount
    )
    {
        AddRange(currentPageItems);
        TotalItemCount = totalItemCount;
        CurrentPageIndex = pageIndex;
        PageSize = pageSize;
    }

    /// <summary>
    /// 使用要分页的所有数据项、当前页索引和每页显示的记录数初始化PagedList对象
    /// </summary>
    /// <param name="allItems">要分页的所有数据项</param>
    /// <param name="pageIndex">当前页索引</param>
    /// <param name="pageSize">每页显示的记录数</param>
    public PagedList(IQueryable<T> allItems, int pageIndex, int pageSize)
    {
        var startIndex = (pageIndex - 1) * pageSize;
        AddRange(allItems.Skip(startIndex).Take(pageSize));
        TotalItemCount = allItems.Count();
        CurrentPageIndex = pageIndex;
        PageSize = pageSize;
    }

    /// <summary>
    /// 使用当前页数据项、当前页索引、每页显示的记录数和要分页的总记录数初始化PagedList对象
    /// </summary>
    /// <param name="currentPageItems">当前页数据项</param>
    /// <param name="pageIndex">当前页索引</param>
    /// <param name="pageSize">每页显示的记录数</param>
    /// <param name="totalItemCount">要分页数据的总记录数</param>
    public PagedList(
        IQueryable<T> currentPageItems,
        int pageIndex,
        int pageSize,
        int totalItemCount
    )
    {
        AddRange(currentPageItems);
        TotalItemCount = totalItemCount;
        CurrentPageIndex = pageIndex;
        PageSize = pageSize;
    }

    /// <summary>
    /// 当前页索引
    /// </summary>
    [IgnoreMember]
    public int CurrentPageIndex { get; set; }

    /// <summary>
    /// 每页显示的记录数
    /// </summary>
    [IgnoreMember]
    public int PageSize { get; set; }

    /// <summary>
    /// 要分页的数据总数
    /// </summary>
    [IgnoreMember]
    public int TotalItemCount { get; set; }

    /// <summary>
    /// 总页数
    /// </summary>
    [IgnoreMember]
    public int TotalPageCount => (int)Math.Ceiling(TotalItemCount / (double)PageSize);

    /// <summary>
    /// 开始记录索引
    /// </summary>
    [IgnoreMember]
    public int StartItemIndex => (CurrentPageIndex - 1) * PageSize + 1;

    /// <summary>
    /// 是否有上一页
    /// </summary>
    [IgnoreMember]
    public bool HasNextPage => CurrentPageIndex < TotalPageCount;

    /// <summary>
    /// 结束记录索引
    /// </summary>
    [IgnoreMember]
    public int EndItemIndex =>
        TotalItemCount > CurrentPageIndex * PageSize ? CurrentPageIndex * PageSize : TotalItemCount;

    public static PagedList<T> Empty() => new(new List<T>(), 0, 0);

    public PagedList()
    {
        AddRange([]);
        CurrentPageIndex = 0;
        PageSize = 0;
    }

    public PagedListWarp<T> ToPagedListWarp()
    {
        return new PagedListWarp<T>(CurrentPageIndex, PageSize, TotalItemCount, this);
    }
}