using DocumentFormat.OpenXml.Packaging;
using DocumentFormat.OpenXml.Spreadsheet;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;

namespace ExcelHelperFW
{
    public class ExcelHelper
    {
        private static readonly ExcelHelper _instance = new ExcelHelper();

        public static ExcelHelper Instance { get { return _instance; } }

        /// <summary>
        /// Get excel data
        /// </summary>
        /// <param name="sourcePath">excel path</param>
        /// <param name="sheetName">sheet name</param>
        /// <param name="rowStartPosition">row start position (first row = 1)</param>
        /// <param name="tempPath">copy path</param>
        /// <returns></returns>
        /// <exception cref="Exception"></exception>
        public List<Dictionary<string, string>> GetData(string sourcePath, string sheetName, bool removeHeader, int rowStartPosition = 1, Func<Dictionary<string, string>, bool> continueFunc = null, string tempPath = "./temp_file.xlsx")
        {
            File.Copy(sourcePath, tempPath, true);

            List<Dictionary<string, string>> data = new List<Dictionary<string, string>>();

            StringBuilder sb = new StringBuilder();
            using (SpreadsheetDocument doc = SpreadsheetDocument.Open(tempPath, true))
            {
                WorkbookPart workbookPart = doc.WorkbookPart;
                Sheet sheet = workbookPart.Workbook.Descendants<Sheet>().FirstOrDefault(s => s.Name == sheetName);

                if (sheet == null)
                    throw new Exception($"Cannot find sheet. (Sheet name: {sheetName})");

                WorksheetPart worksheetPart = (WorksheetPart)workbookPart.GetPartById(sheet.Id);
                Worksheet worksheet = worksheetPart.Worksheet;

                List<Row> rows = worksheet.Descendants<Row>().Where(r => r.RowIndex >= rowStartPosition).ToList();
                if (removeHeader)
                    rows.RemoveAt(0);

                for (int i = 0; i < rows.Count; i++)
                {
                    Dictionary<string, string> rowPairs = RowToKeyValuePairs(rows[i], workbookPart);
                    if (rowPairs == null || rowPairs.Count < 1)
                        continue;

                    if (continueFunc != null && continueFunc(rowPairs))
                        continue;

                    data.Add(rowPairs);
                }
            }

            return data;
        }

        private Dictionary<string, string> RowToKeyValuePairs(Row row, WorkbookPart workbookPart)
        {
            Dictionary<string, string> pairs = new Dictionary<string, string>();
            var cells = row.Elements<Cell>().ToList();

            for (int col = 0; col < cells.Count; col++)
            {
                Cell cell = cells[col];

                string cellReference = cell.CellReference.Value;
                string columnName = Regex.Replace(cellReference, @"\d", "");
                //int rowNumber = int.Parse(Regex.Replace(cellReference, "[^0-9]", ""));

                string cellValue = cell.CellValue?.InnerText;
                if (cell.DataType != null && cell.DataType.Value == CellValues.SharedString)
                {
                    int.TryParse(cellValue, out int sharedStringId);
                    cellValue = workbookPart.SharedStringTablePart.SharedStringTable.Elements<SharedStringItem>().ElementAt(sharedStringId).InnerText;
                }

                pairs.Add(columnName, cellValue);
            }

            return pairs;
        }

        public string ConvertValue(Dictionary<string, string> pairs, string key)
        {
            if (!pairs.ContainsKey(key))
                return null;

            return pairs[key];
        }

        public T ConvertValue<T>(Dictionary<string, string> pairs, string key, Func<string, T> func)
        {
            if (!pairs.ContainsKey(key) || func == null)
                return default(T);

            string value = pairs[key];
            return func(value);
        }

        public DateTime? ConvertValueToDateTime(Dictionary<string, string> pairs, string key)
        {
            return ConvertValue<DateTime?>(pairs, key, x =>
            {
                if (string.IsNullOrEmpty(x))
                    return null;

                if (double.TryParse(x, out double d))
                    return DateTime.FromOADate(d);
                else
                    return null;
            });
        }
    }
}