using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Hncore.Infrastructure.Data;
using Hncore.Infrastructure.Extension;
using Microsoft.EntityFrameworkCore;

namespace Hncore.Infrastructure.EntitiesExtension
{
    public static class IQueryableExtend
    {
        #region 返回IQueryable<T>前几条数据

        /// <summary>
        /// 返回IQueryable前几条数据
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="query"></param>
        /// <param name="TopN"></param>
        /// <returns></returns>
        public static IQueryable<T> TopN<T>(this IQueryable<T> query, int TopN)
        {
            return query.Take(TopN);
        }

        #endregion

        #region 对IQueryable<T>进行分页

        /// <summary>
        /// 对IQueryable进行分页
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="query"></param>
        /// <param name="PageSize">每页多少条数据</param>
        /// <param name="PageIndex">当前页</param>
        /// <returns></returns>
        public static IQueryable<T> QueryPager<T>(this IQueryable<T> query, int PageSize, int PageIndex)
        {
            if (PageIndex <= 0)
            {
                PageIndex = 1;
            }

            if (PageSize <= 0)
            {
                PageSize = 1;
            }

            if (PageSize > 0)
                return query.Skip((PageIndex - 1) * PageSize).Take(PageSize);
            return query;
        }

        #endregion

        #region 得到IQueryable<T>的分页后实体集合

        /// <summary>
        /// 得到IQueryable的分页后实体集合
        /// </summary>
        /// <param name="query"></param>
        /// <param name="pageSize">每页多少条数据</param>
        /// <param name="pageIndex">当前页</param>
        /// <param name="isTotal">是否统计总行数</param>
        /// <returns></returns>
        public static PageData<T> ListPager<T>(this IQueryable<T> query, int pageSize, int pageIndex, bool isTotal)
        {
            PageData<T> list = new PageData<T>();

            if (isTotal)
            {
                list.RowCount = query.Count();
            }

            list.List = query.QueryPager<T>(pageSize, pageIndex).ToList();

            return list;
        }

        /// <summary>
        /// 得到IQueryable的分页后实体集合
        /// </summary>
        /// <param name="query"></param>
        /// <param name="pageSize">每页多少条数据</param>
        /// <param name="pageIndex">当前页</param>
        /// <param name="isTotal">是否统计总行数</param>
        /// <returns></returns>
        public static async Task<PageData<T>> ListPagerAsync<T>(this IQueryable<T> query, int pageSize, int pageIndex,
            bool isTotal)
        {
            PageData<T> list = new PageData<T>();

            if (isTotal)
            {
                list.RowCount = await query.CountAsync();
            }

            list.List = await query.QueryPager<T>(pageSize, pageIndex).ToListAsync();

            return list;
        }

        #endregion
    }
}