using NPOI.SS.UserModel;
using System;
using System.Data;
using System.IO;

namespace YiDa_WinForm.Utils
{
    /// <summary>
    /// Excel 解析工具类
    /// </summary>
    public static class ExcelHelper
    {
        /// <summary>
        /// 解析Excel为DataTable
        /// </summary>
        public static DataTable GetExcel(string filePath)
        {
            IWorkbook iwkX = null;
            DataTable dt = new DataTable();
            try
            {
                // 使用 using 包裹 FileStream，确保资源快速释放，且减少文件占用
                using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite,
                           4096, FileOptions.SequentialScan))
                {
                    iwkX = WorkbookFactory.Create(fs);
                }

                if (iwkX == null || iwkX.NumberOfSheets == 0)
                {
                    LogHelper.AppendLog("Excel文件中无Sheet，解析为空");
                    return dt;
                }

                ISheet sheet = iwkX.GetSheetAt(0);
                if (sheet.LastRowNum < 1) // 无数据行（仅表头）
                {
                    LogHelper.AppendLog("Excel文件中无有效数据行");
                    return dt;
                }

                // 读取表头（减少重复判断）
                IRow headerRow = sheet.GetRow(0);
                for (int i = 0; i < headerRow.LastCellNum; i++)
                {
                    ICell cell = headerRow.GetCell(i);
                    string columnName = cell == null ? $"未知列_{i}" : cell.ToString().Trim();
                    if (dt.Columns.Contains(columnName))
                    {
                        columnName += $"_{i}";
                    }

                    dt.Columns.Add(columnName);
                }

                // 批量读取数据行，减少空行判断的冗余操作
                int startRow = 1; // 跳过表头
                for (int i = startRow; i <= sheet.LastRowNum; i++)
                {
                    IRow dataRow = sheet.GetRow(i);
                    if (dataRow == null) continue;

                    DataRow dr = dt.NewRow();
                    bool isEmptyRow = true; // 空行标记

                    for (int j = 0; j < dt.Columns.Count; j++)
                    {
                        ICell cell = dataRow.GetCell(j, MissingCellPolicy.CREATE_NULL_AS_BLANK);
                        string cellValue = cell.ToString().Trim();
                        dr[j] = cellValue;

                        // 优化4：只要有一个单元格非空，就不是空行（减少后续 All 遍历）
                        if (!string.IsNullOrEmpty(cellValue))
                        {
                            isEmptyRow = false;
                        }
                    }

                    if (!isEmptyRow)
                    {
                        dt.Rows.Add(dr);
                    }
                }

                LogHelper.AppendLog($"Excel解析成功：{dt.Rows.Count}行数据，{dt.Columns.Count}列");
            }
            catch (Exception ex)
            {
                LogHelper.AppendLog($"Excel解析失败：{ex.Message}");
            }
            finally
            {
                iwkX?.Close();
            }

            return dt;
        }
    }
}