using NPOI.HSSF.UserModel;
using NPOI.SS.Formula.Constant;
using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
using System;
using System.Data;
using System.IO;

namespace CaeKnowledge
{
    public class NpoiExcelImportHelper
    {
        private static NpoiExcelImportHelper _excelImportHelper;

        public static NpoiExcelImportHelper Self
        {
            get => _excelImportHelper ?? (_excelImportHelper = new NpoiExcelImportHelper());
            set => _excelImportHelper = value;
        }

        /// <summary>
        /// 读取excel表格中的数据,将Excel文件流转化为dataTable数据源  
        /// 默认第一行为标题 
        /// </summary>
        /// <param name="stream">excel文档文件流</param>
        /// <param name="fileType">文档格式</param>
        /// <param name="isSuccess">是否转化成功</param>
        /// <param name="resultMsg">转换结果消息</param>
        /// <returns></returns>
        public DataTable ExcelToDataTable(Stream stream, string fileType, out bool isSuccess, out string resultMsg)
        {
            isSuccess = false;
            resultMsg = "Excel文件流成功转化为DataTable数据源";

            var excelToDataTable = new DataTable();

            try
            {
                // Workbook对象代表一个工作簿,首先定义一个Excel工作薄
                IWorkbook workbook;

                // XSSFWorkbook 适用XLSX格式，HSSFWorkbook 适用XLS格式
                #region 判断Excel版本
                switch (fileType)
                {
                    //.XLSX是07版(或者07以上的)的Office Excel
                    case ".xlsx":
                        workbook = new XSSFWorkbook(stream);
                        break;
                    //.XLS是03版的Office Excel
                    case ".xls":
                        workbook = new HSSFWorkbook(stream);
                        break;
                    default:
                        throw new Exception("Excel文档格式有误");
                }
                #endregion 判断Excel版本

                var sheet = workbook.GetSheetAt(0);
                // var rows = sheet.GetRowEnumerator();

                var headerRow = sheet.GetRow(0);
                int cellCount = headerRow.LastCellNum;//最后一行列数（即为总列数）

                //获取第一行标题列数据源,转换为dataTable数据源的表格标题名称
                for (var j = 0; j < cellCount; j++)
                {
                    var cell = headerRow.GetCell(j);
                    DataColumn column = excelToDataTable.Columns.Add(cell.ToString());
                    if (j == 0)
                    {
                        column.Unique = true;
                    }
                }

                //获取Excel表格中除标题以为的所有数据源，转化为dataTable中的表格数据源
                for (var i = sheet.FirstRowNum + 1; i <= sheet.LastRowNum; i++)
                {
                    var dataRow = excelToDataTable.NewRow();

                    var row = sheet.GetRow(i);

                    if (row == null) continue; //没有数据的行默认是null　

                    for (int j = row.FirstCellNum; j < cellCount; j++)
                    {
                        if (row.GetCell(j) != null)//单元格内容非空验证
                        {
                            #region NPOI获取Excel单元格中不同类型的数据
                            //获取指定的单元格信息
                            var cell = row.GetCell(j);
                            switch (cell.CellType)
                            {
                                //首先在NPOI中数字和日期都属于Numeric类型
                                //通过NPOI中自带的DateUtil.IsCellDateFormatted判断是否为时间日期类型
                                case CellType.Numeric when DateUtil.IsCellDateFormatted(cell):
                                    dataRow[j] = cell.DateCellValue;
                                    break;
                                case CellType.Numeric:
                                    //其他数字类型
                                    dataRow[j] = cell.NumericCellValue;
                                    break;
                                //空数据类型
                                case CellType.Blank:
                                    dataRow[j] = "";
                                    break;
                                //公式类型
                                case CellType.Formula:
                                {
                                    IFormulaEvaluator eva = ".xlsx" == fileType ? (IFormulaEvaluator)new XSSFFormulaEvaluator(workbook) : new HSSFFormulaEvaluator(workbook);
                                    dataRow[j] = eva.Evaluate(cell).StringValue;
                                    break;
                                }
                                //布尔类型
                                case CellType.Boolean:
                                    dataRow[j] = row.GetCell(j).BooleanCellValue;
                                    break;
                                //错误
                                case CellType.Error:
                                    dataRow[j] = ErrorConstant.ValueOf(row.GetCell(j).ErrorCellValue);
                                    break;
                                //其他类型都按字符串类型来处理（未知类型CellType.Unknown，字符串类型CellType.String）
                                default:
                                    dataRow[j] = cell.StringCellValue;
                                    break;
                            }
                            #endregion
                        }
                    }
                    excelToDataTable.Rows.Add(dataRow);
                }

                isSuccess = true;
            }
            catch (Exception e)
            {
                resultMsg = e.Message;
            }

            return excelToDataTable;
        }
    }
}