using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using XP.Common.Database.Models;

namespace XP.Common.Database.Helpers
{
    /// <summary>
    /// 分页计算辅助工具
    /// </summary>
    public static class PaginationHelper
    {
        /// <summary>
        /// 计算分页偏移量（SQLite OFFSET）
        /// </summary>
        public static int CalculateOffset(PaginationRequest pagination)
        {
            if (pagination.PageIndex < 1) pagination.PageIndex = 1;
            if (pagination.PageSize < 1) pagination.PageSize = 20;
            return (pagination.PageIndex - 1) * pagination.PageSize;
        }

        /// <summary>
        /// 验证并修正分页参数
        /// </summary>
        public static PaginationRequest ValidateAndFix(PaginationRequest pagination)
        {
            var fixedPagination = new PaginationRequest
            {
                PageIndex = pagination.PageIndex < 1 ? 1 : pagination.PageIndex,
                PageSize = pagination.PageSize < 1 ? 20 : (pagination.PageSize > 1000 ? 1000 : pagination.PageSize),
                OrderBy = pagination.OrderBy ?? string.Empty
            };
            return fixedPagination;
        }
    }
}