using NPOI.HSSF.UserModel;
using NPOI.SS.Formula.Functions;
using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
using System;
using System.Collections.Generic;
using System.Data.Common;
using System.IO;
using System.Linq;
using System.Web;
using WebLib;

namespace Education
{
    public class ImportBase
    {
        protected WebLib.Excel excel;
        protected List<ImportColumn> columns;
        private static string importFilePath = "~/DocUpload/Import";
        protected DbConnection connection;
        protected static List<string> trueValues = new List<string>() { "Y", "V", "T", "1", "YES", "TRUE" };

        public const double MinOADate = 43831.0;     // 2020/01/01
        public const double MaxOADate = 2958465.0;   // 9999/12/31

        public ImportBase()
        {
            excel = new WebLib.Excel();
            columns = new List<ImportColumn>();
        }

        public DbConnection Connection
        {
            get { return connection; }
            set { connection = value; }
        }

        public static string ImportFilePath
        {
            get
            {
                var fullPath = HttpContext.Current.Server.MapPath(importFilePath);
                if (!Directory.Exists(fullPath))
                {
                    Directory.CreateDirectory(fullPath);
                }

                return fullPath;
            }
        }

        public MemoryStream ImportExample()
        {
            var workbook = new XSSFWorkbook();
            var sheet = workbook.CreateSheet("匯入範例");
            excel.Sheet = sheet;
            int col = 0;
            foreach (var column in columns)
            {
                excel.SetCellValue(0, col, column.Title);
                excel.SetColumnWidthInChars(col, column.Width);
                col++;
            }
            MemoryStream ms = new MemoryStream();
            workbook.Write(ms);
            return ms;
        }

        public IWorkbook LoadWorkbook(string filePath)
        {
            using (FileStream file = new FileStream(filePath, FileMode.Open, FileAccess.Read))
            {
                if (Path.GetExtension(filePath).ToLower() == ".xls")
                {
                    return new HSSFWorkbook(file);
                }
                else if (Path.GetExtension(filePath).ToLower() == ".xlsx")
                {
                    return new XSSFWorkbook(file);
                }
                else
                {
                    throw new Exception("不支援的檔案格式");
                }
            }
        }

        public List<string> Validate(string filePath, Type type, out int rowCount)
        {
            // 1. 開啟 Excel 檔案
            var workbook = LoadWorkbook(filePath);
            // 2. 讀取第一個工作表
            var sheet = workbook.GetSheetAt(0);
            // 3. 驗證欄位名稱
            var headerRow = sheet.GetRow(0);
            var errors = ValidateColumns(headerRow, out var columnMap);
            // 4. 驗證每一列資料
            rowCount = 0;
            for (int rowId = 1; rowId <= sheet.LastRowNum; rowId++)
            {
                var row = sheet.GetRow(rowId);
                if (row == null)
                {
                    break;

                }
                var rowErrors = ValidateRow(row, type, columnMap, out bool stop);
                foreach (var err in rowErrors)
                {
                    errors.Add($"第 {rowId} 列：{err}");
                }
                rowCount++;
                if (stop)
                {
                    break;
                }
            }
            if (rowCount == 0)
            {
                errors.Add("沒有任何資料列");
            }
            // 5. 回傳錯誤訊息清單
            return errors;
        }

        public List<string> ValidateColumns(IRow headerRow, out Dictionary<string, int> columnMap)
        {
            List<string> errors = new List<string>();
            columnMap = new Dictionary<string, int>();

            // 建立標題 → 欄位索引的對照表
            if (headerRow != null)
            {
                for (int i = 0; i <= headerRow.LastCellNum; i++)
                {
                    var cell = headerRow.GetCell(i);
                    if (cell == null) continue;
                    string title = cell.ToString().Trim();
                    if (!string.IsNullOrEmpty(title) && !columnMap.ContainsKey(title))
                    {
                        columnMap[title] = i;
                    }
                }
            }

            // 確認每個必要欄位都存在於標頭列
            foreach (var column in columns)
            {
                if (!columnMap.ContainsKey(column.Title))
                {
                    errors.Add($"找不到欄位「{column.Title}」");
                }
            }
            return errors;
        }

        public List<string> ValidateRow(IRow dataRow, Type type, Dictionary<string, int> columnMap, out bool stop)
        {
            stop = false;
            List<string> errors = new List<string>();

            // 以欄位名稱取得每欄的值
            var cellValues = new Dictionary<string, string>();
            foreach (var column in columns)
            {
                string cellValue = "";
                if (columnMap.ContainsKey(column.Title))
                {
                    var cell = dataRow.GetCell(columnMap[column.Title]);
                    cellValue = cell == null ? "" : excel.CellValueToString(cell);
                }
                cellValues[column.Title] = cellValue;
            }

            // 若所有欄位皆為空則回傳停止旗標
            bool allEmpty = true;
            foreach (var v in cellValues.Values)
            {
                if (!string.IsNullOrEmpty(v)) { allEmpty = false; break; }
            }
            if (allEmpty)
            {
                stop = true;
                return errors;
            }

            foreach (var column in columns)
            {
                string cellValue = cellValues[column.Title];
                if (column.Required && string.IsNullOrEmpty(cellValue))
                {
                    errors.Add($"欄位「{column.Title}」為必填欄位");
                }

                // 應用 TransformFunction（如果設定）
                if (column.TransformFunction != null)
                {
                    cellValue = column.TransformFunction(cellValue)?.ToString() ?? "";
                }

                if (!string.IsNullOrEmpty(cellValue))
                {
                    var property = type.GetProperty(column.FieldName);
                    if (property != null)
                    {
                        try
                        {
                            var targetType = property.PropertyType;
                            if (targetType.IsGenericType && targetType.GetGenericTypeDefinition() == typeof(Nullable<>))
                            {
                                targetType = Nullable.GetUnderlyingType(targetType);
                            }
                            if (targetType == typeof(DateTime))
                            {
                                ParseExcelDate(cellValue);
                            }
                            else
                            {
                                Convert.ChangeType(cellValue, targetType);
                            }
                        }
                        catch
                        {
                            var typeName = property.PropertyType.Name;
                            if (property.PropertyType.IsGenericType && property.PropertyType.GetGenericTypeDefinition() == typeof(Nullable<>))
                            {
                                var underlying = Nullable.GetUnderlyingType(property.PropertyType);
                                typeName = $"{underlying.Name}（可空）";
                            }
                            errors.Add($"欄位「{column.Title}」的值「{cellValue}」應該是 {typeName} 類型".Replace("<", "&lt;").Replace(">", "&gt;"));
                        }
                    }
                }
            }
            return errors;
        }

        public List<T> ReadRows<T>(string filePath, int beginRow = 1) where T : new() 
        {
            var workbook = LoadWorkbook(filePath);
            excel.Sheet = workbook.GetSheetAt(0);
            var result = new List<T>();

            // 從標頭列建立欄位名稱 → 欄位索引對照表
            var columnMap = new Dictionary<string, int>();
            var headerRow = excel.Sheet.GetRow(0);
            if (headerRow != null)
            {
                for (int i = 0; i <= headerRow.LastCellNum; i++)
                {
                    var cell = headerRow.GetCell(i);
                    if (cell == null) continue;
                    string title = cell.ToString().Trim();
                    if (!string.IsNullOrEmpty(title) && !columnMap.ContainsKey(title))
                    {
                        columnMap[title] = i;
                    }
                }
            }

            for (int r = beginRow; r <= excel.Sheet.LastRowNum; r++)
            {
                var row = excel.Sheet.GetRow(r);
                if (row == null)
                {
                    break;
                }

                // 以欄位名稱取得每欄的值
                var cellValues = new Dictionary<string, string>();
                foreach (var column in columns)
                {
                    string cellValue = "";
                    if (columnMap.ContainsKey(column.Title))
                    {
                        var cell = row.GetCell(columnMap[column.Title]);
                        cellValue = cell == null ? "" : excel.CellValueToString(cell);
                    }
                    cellValues[column.Title] = cellValue;
                }

                // 若所有欄位皆為空則停止
                bool allEmpty = true;
                foreach (var v in cellValues.Values)
                {
                    if (!string.IsNullOrEmpty(v)) { allEmpty = false; break; }
                }
                if (allEmpty)
                {
                    break;
                }

                var item = new T();
                foreach (var column in columns)
                {
                    string cellValue = cellValues[column.Title];

                    // 假設 T 有對應的屬性名稱與欄位標題相同
                    var property = typeof(T).GetProperty(column.FieldName);
                    if (property != null)
                    {
                        object valueToSet = null;
                        if (column.TransformFunction != null)
                        {
                            valueToSet = column.TransformFunction(cellValue);
                        }
                        else
                        {
                            if (string.IsNullOrEmpty(cellValue))
                            {
                                if (property.PropertyType.IsGenericType && property.PropertyType.GetGenericTypeDefinition() == typeof(Nullable<>))
                                {
                                    valueToSet = null;
                                }
                                else
                                {
                                    // 對於非 Nullable 類型，如果為空則跳過設定
                                    continue;
                                }
                            }
                            else
                            {
                                var targetType = property.PropertyType;
                                if (targetType.IsGenericType && targetType.GetGenericTypeDefinition() == typeof(Nullable<>))
                                {
                                    targetType = Nullable.GetUnderlyingType(targetType);
                                }
                                if (targetType == typeof(DateTime))
                                {
                                    valueToSet = ParseExcelDate(cellValue);
                                }
                                else
                                {
                                    valueToSet = Convert.ChangeType(cellValue, targetType);
                                }
                            }
                        }
                        property.SetValue(item, valueToSet, null);
                    }
                }
                result.Add(item);
            }

            return result;
        }

        private static DateTime ParseExcelDate(string value)
        {
            if (DateTime.TryParse(value, out DateTime dt))
            {
                return dt;
            }
            if (double.TryParse(value, out double d) && d >= MinOADate && d <= MaxOADate)
            {
                return DateTime.FromOADate(d);
            }
            throw new FormatException($"無法將「{value}」轉換為日期");
        }

        public virtual T SelectExisting<T>(T item) where T : new()
        { 
            throw new NotImplementedException("請在子類別中實作此方法以選取現有資料");
        }

        public virtual void InsertOne<T>(T item) where T : new()
        {
            throw new NotImplementedException("請在子類別中實作此方法以新增資料");
        }

        public virtual void UpdateOne<T>(T newItem, T existingItem) where T : new()
        {
            throw new NotImplementedException("請在子類別中實作此方法以更新資料");
        }

        public virtual string ImportRowErrorMessage<T>(T item, string errorMessage) where T : new()
        {
            return $"資料 {item.ToString()} 匯入失敗，錯誤原因：{errorMessage}";
        }

        public bool Import<T>(string filePath, 
            out string message,            
            int beginRow = 1) where T : new()
        {
            var importErrors = new List<string>();
            message = "";
            var insertCount = 0;
            var updateCount = 0;

            var rows = ReadRows<T>(filePath, beginRow);
            if (rows.Count == 0)
            {
                importErrors.Add("匯入檔案中沒有任何資料");
                return false;
            }

            using (var ts = DAC.NewTransactionScope())
            {
                foreach (var row in rows)
                {
                    try
                    {
                        var existing = SelectExisting(row);
                        if (existing == null)
                        {
                            InsertOne(row);
                            insertCount++;
                        }
                        else
                        {
                            UpdateOne(row, existing);
                            updateCount++;
                        }
                    }
                    catch (Exception ex)
                    {
                        importErrors.Add(ImportRowErrorMessage(row, ex.Message));
                    }
                }
            }

            if (importErrors.Count == 0)
            {
                message = $"資料匯入成功，共新增 {insertCount} 筆資料，修改 {updateCount} 筆資料。";
                return true;
            }
            else
            {
                message = $"資料匯入完成，共新增 {insertCount} 筆資料，修改 {updateCount} 筆資料，但有以下錯誤:<br/>" + string.Join("<br/>", importErrors.ToArray());
                return false;
            }
        }

        /// <summary>
        /// 真假值轉換函數，把代表真值的字串轉換成 1，否則轉換成 0
        /// </summary>
        protected TransformFunction BoolTransform = (input) =>
        {
            if (string.IsNullOrEmpty(input)) return 0;
            var inputStr = input.ToUpper();
            return trueValues.Contains(inputStr) ? 1 : 0;
        };
    }

    // 新增委派定義
    public delegate object TransformFunction(string input);

    public class ImportColumn
    {
        public string Title { get; set; }
        public int Width { get; set; }
        public string FieldName { get; set; }
        public bool Required { get; set; }
        public TransformFunction TransformFunction { get; set; }
        public ImportColumn(string title, int width, bool required = false, string fieldName = null, TransformFunction transformFunction = null)
        {
            Title = title;
            Width = width;
            Required = required;
            FieldName = fieldName ?? title;
            TransformFunction = transformFunction;
        }
    }
}