using NPOI.SS.UserModel;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Web;
using System.Text.RegularExpressions;

namespace 報到系統
{
    public class FileUploadHandler : IHttpHandler
    {
        public void ProcessRequest(HttpContext context)
        {
            try
            {
                string action = context.Request.QueryString["action"];
                
                if (action == "ProcessImportFile")
                {
                    ProcessImportFile(context);
                }
                else
                {
                    SendJsonResponse(context, new BaseResponse
                    {
                        Success = false,
                        Message = "無效的操作"
                    });
                }
            }
            catch (Exception ex)
            {
                SendJsonResponse(context, new BaseResponse
                {
                    Success = false,
                    Message = "處理請求發生錯誤：" + ex.Message
                });
            }
        }

        /// <summary>
        /// 處理匯入檔案 - 讀取 Excel 檔案並進行驗證，使用 NPOI
        /// </summary>
        private void ProcessImportFile(HttpContext context)
        {
            try
            {
                string courseIDStr = context.Request.QueryString["courseID"];
                if (!int.TryParse(courseIDStr, out int courseID) || courseID <= 0)
                {
                    SendJsonResponse(context, new BaseResponse
                    {
                        Success = false,
                        Message = "活動編號為必填欄位"
                    });
                    return;
                }

                // 檢查是否有上傳檔案
                if (context.Request.Files.Count == 0)
                {
                    SendJsonResponse(context, new BaseResponse
                    {
                        Success = false,
                        Message = "沒有上傳檔案"
                    });
                    return;
                }

                HttpPostedFile file = context.Request.Files[0];
                if (file.ContentLength == 0)
                {
                    SendJsonResponse(context, new BaseResponse
                    {
                        Success = false,
                        Message = "檔案為空"
                    });
                    return;
                }

                // 驗證檔案格式
                string fileName = Path.GetFileName(file.FileName);
                if (!fileName.ToLower().EndsWith(".xlsx") && !fileName.ToLower().EndsWith(".xls"))
                {
                    SendJsonResponse(context, new BaseResponse
                    {
                        Success = false,
                        Message = "只支援 .xlsx 或 .xls 格式的 Excel 檔案"
                    });
                    return;
                }

                // 使用 NPOI 讀取 Excel 檔案
                IWorkbook workbook = WorkbookFactory.Create(file.InputStream);
                ISheet sheet = workbook.GetSheetAt(0);

                List<Dictionary<string, object>> previewData = new List<Dictionary<string, object>>();
                List<string> validationErrors = new List<string>();
                int headerRowIndex = -1;

                // 偵測表頭並讀取資料
                for (int rowIndex = 0; rowIndex <= sheet.LastRowNum; rowIndex++)
                {
                    IRow row = sheet.GetRow(rowIndex);
                    if (row == null) continue;

                    // 欄位順序: 序號(0), 學員姓名(1), 手機號(2), 身分別(5), 身分證字號(6), 餐點(7), 電子郵件(8), 失業給付認定次數(9), 性別(10)
                    string indexValue = GetCellValue(row.GetCell(0))?.Trim();
                    string nameValue = GetCellValue(row.GetCell(1))?.Trim();
                    string mobileValue = GetCellValue(row.GetCell(2))?.Trim();
                    string idTypeValue = GetCellValue(row.GetCell(5))?.Trim();
                    string idNumberValue = GetCellValue(row.GetCell(6))?.Trim();
                    string mealTypeValue = GetCellValue(row.GetCell(7))?.Trim();
                    string emailValue = GetCellValue(row.GetCell(8))?.Trim();
                    string lossJobTimesValue = GetCellValue(row.GetCell(9))?.Trim();
                    string genderValue = GetCellValue(row.GetCell(10))?.Trim();

                    // 偵測表頭 - 檢查第1欄和第2欄
                    if (headerRowIndex < 0 && IsHeaderRow(indexValue, nameValue))
                    {
                        headerRowIndex = rowIndex;
                        continue;
                    }

                    // 跳過表頭之前的行
                    if (headerRowIndex < 0) continue;

                    // 跳過空行
                    if (string.IsNullOrEmpty(nameValue) && string.IsNullOrEmpty(mobileValue))
                        continue;

                    // 驗證資料
                    List<string> rowErrors = new List<string>();
                    int dataRowIndex = rowIndex - headerRowIndex;

                    if (string.IsNullOrEmpty(nameValue?.Trim()))
                    {
                        rowErrors.Add($"第 {dataRowIndex} 列：姓名為必填欄位");
                        validationErrors.Add(rowErrors[rowErrors.Count - 1]);
                    }
                    else if (nameValue.Length > 100)
                    {
                        rowErrors.Add($"第 {dataRowIndex} 列：姓名最長 100 個字元");
                        validationErrors.Add(rowErrors[rowErrors.Count - 1]);
                    }

                    if (string.IsNullOrEmpty(mobileValue?.Trim()))
                    {
                        rowErrors.Add($"第 {dataRowIndex} 列：手機號為必填欄位");
                        validationErrors.Add(rowErrors[rowErrors.Count - 1]);
                    }
                    else
                    {
                        // 清洗資料，只保留數字
                        mobileValue = Regex.Replace(mobileValue, @"\D", "");

                        if (!Regex.IsMatch(mobileValue.Trim(), @"^09\d{8}$"))
                        {
                            rowErrors.Add($"第 {dataRowIndex} 列：手機號格式必須為 09 開頭的 10 位數字");
                            validationErrors.Add(rowErrors[rowErrors.Count - 1]);
                        }
                    }

                    // 驗證身分證字號（如果有填寫）
                    if (!string.IsNullOrEmpty(idNumberValue?.Trim()))
                    {
                        if (!ValidateIDNumber(idNumberValue.ToUpper().Trim()))
                        {
                            rowErrors.Add($"第 {dataRowIndex} 列：身分證字號無效（格式應為：大寫英文字母 + 9位數字，且檢查碼需正確）");
                            validationErrors.Add(rowErrors[rowErrors.Count - 1]);
                        }
                    }

                    // 驗證電子郵件（如果有填寫）
                    if (!string.IsNullOrEmpty(emailValue?.Trim()))
                    {
                        if (!ValidateEmail(emailValue.Trim()))
                        {
                            rowErrors.Add($"第 {dataRowIndex} 列：電子郵件格式不正確（例如：user@example.com）");
                            validationErrors.Add(rowErrors[rowErrors.Count - 1]);
                        }
                    }

                    // 驗證失業給付認定次數（如果有填寫）
                    if (!string.IsNullOrEmpty(lossJobTimesValue?.Trim()))
                    {
                        if (!int.TryParse(lossJobTimesValue, out int i))
                        {
                            rowErrors.Add($"第 {dataRowIndex} 列：失業給付認定次數必須為數字");
                            validationErrors.Add(rowErrors[rowErrors.Count - 1]);
                        }

                        if (i < 0)
                        {
                            rowErrors.Add($"第 {dataRowIndex} 列：失業給付認定次數必須大於或等於 0");
                            validationErrors.Add(rowErrors[rowErrors.Count - 1]);
                        }
                    }

                    var rowData = new Dictionary<string, object>();
                    rowData["Name"] = nameValue;
                    rowData["Mobile"] = mobileValue;
                    rowData["IDType"] = idTypeValue;
                    rowData["IDNumber"] = idNumberValue?.ToUpper();
                    rowData["MealType"] = mealTypeValue;
                    rowData["Email"] = emailValue;
                    rowData["LossJobTimes"] = lossJobTimesValue;
                    rowData["Gender"] = genderValue;
                    rowData["SignUpType"] = "預約";
                    rowData["Errors"] = rowErrors;
                    rowData["IsValid"] = rowErrors.Count == 0;
                    previewData.Add(rowData);
                }

                workbook.Close();

                int validRowCount = 0;
                foreach (var item in previewData)
                {
                    if ((bool)item["IsValid"])
                    {
                        validRowCount++;
                    }
                }

                SendJsonResponse(context, new BaseResponse
                {
                    Success = true,
                    Message = "檔案讀取成功",
                    Data = new
                    {
                        PreviewData = previewData,
                        ValidationErrors = validationErrors,
                        ValidRowCount = validRowCount,
                        TotalRowCount = previewData.Count
                    }
                });
            }
            catch (Exception ex)
            {
                SendJsonResponse(context, new BaseResponse
                {
                    Success = false,
                    Message = "處理匯入檔案發生錯誤：" + ex.Message
                });
            }
        }

        /// <summary>
        /// 驗證中華民國身分證字號
        /// 規則：第一碼為英文字母（A-Z），後接九位數字
        /// 使用檢查碼算法驗證
        /// </summary>
        private bool ValidateIDNumber(string idNumber)
        {
            if (string.IsNullOrEmpty(idNumber))
                return false;

            idNumber = idNumber.Trim().ToUpper();

            // 檢查長度
            if (idNumber.Length != 10)
                return false;

            // 第一碼必須是英文字母
            if (idNumber[0] < 'A' || idNumber[0] > 'Z')
                return false;

            // 後九碼必須是數字
            for (int i = 1; i < 10; i++)
            {
                if (idNumber[i] < '0' || idNumber[i] > '9')
                    return false;
            }

            // 驗證檢查碼
            // 字母對應的數字
            int[] letterValues = {
                10, 11, 12, 13, 14, 15, 16, 17, 34, 18, 19, 20, 21,
                22, 35, 23, 24, 25, 26, 27, 28, 29, 32, 30, 31, 33
            };

            int code = letterValues[idNumber[0] - 'A'];

            int sum = code / 10 + (code % 10) * 9;

            int[] weights = { 8, 7, 6, 5, 4, 3, 2, 1 };

            for (int i = 1; i <= 8; i++)
            {
                sum += (idNumber[i] - '0') * weights[i - 1];
            }

            sum += idNumber[9] - '0';

            return sum % 10 == 0;
        }

        /// <summary>
        /// 驗證電子郵件格式
        /// </summary>
        private bool ValidateEmail(string email)
        {
            if (string.IsNullOrEmpty(email))
                return true;

            return System.Text.RegularExpressions.Regex.IsMatch(
                email.Trim(), 
                @"^[^\s@]+@[^\s@]+\.[^\s@]+$");
        }

        /// <summary>
        /// 取得單元格的值（文字）
        /// </summary>
        private string GetCellValue(ICell cell)
        {
            if (cell == null) return "";

            try
            {
                switch (cell.CellType)
                {
                    case CellType.String:
                        return cell.StringCellValue;
                    case CellType.Numeric:
                        return cell.NumericCellValue.ToString();
                    case CellType.Boolean:
                        return cell.BooleanCellValue.ToString();
                    default:
                        return "";
                }
            }
            catch
            {
                return "";
            }
        }

        /// <summary>
        /// 判斷是否為表頭行
        /// </summary>
        private bool IsHeaderRow(string col1, string col2)
        {
            // col1 是序號, col2 是學員姓名
            string[] col1Keywords = { "序號", "編號", "index", "Index", "#" };
            string[] col2Keywords = { "姓名", "名字", "name", "Name", "學員" };

            bool isCol1Header = col1Keywords.Any(keyword => 
                (col1 ?? "").ToLower().Contains(keyword.ToLower()));
            bool isCol2Header = col2Keywords.Any(keyword => 
                (col2 ?? "").ToLower().Contains(keyword.ToLower()));

            return isCol1Header || isCol2Header;
        }

        /// <summary>
        /// 發送 JSON 響應
        /// </summary>
        private void SendJsonResponse(HttpContext context, object data)
        {
            context.Response.ContentType = "application/json; charset=utf-8";
            try
            {
                // 使用 JavaScriptSerializer 序列化為 JSON
                System.Web.Script.Serialization.JavaScriptSerializer serializer = 
                    new System.Web.Script.Serialization.JavaScriptSerializer();
                // 設定遞迴深度以支援複雜物件
                serializer.MaxJsonLength = int.MaxValue;
                string json = serializer.Serialize(data);
                context.Response.Write(json);
            }
            catch (Exception ex)
            {
                // 備用的簡單 JSON 序列化
                context.Response.Write("{\"Success\":false,\"Message\":\"序列化錯誤：" + ex.Message.Replace("\"", "\\\"") + "\"}");
            }
        }

        public bool IsReusable
        {
            get { return false; }
        }
    }
}