// Copyright (c) 2022- schick Informatik
// Description: Compares excel files and highlights changes
//

using System;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Drawing;
using Microsoft.Office.Interop.Excel;

namespace ENI2.Excel
{

    /// <summary>
    /// Diese Klasse beinhaltet den von Anmeldungen unabhängigen Vergleich von Excel Sheets. Damit 
    /// können dann Updates von "außen" einfacher abgearbeitet werden. Zellen und sheets werden bei
    /// Aktualisierung bunt eingefärbt
    /// </summary>
    public static class ExcelComparer
    {
        private static int diffColor = ColorTranslator.ToOle(Color.FromArgb(150, 150, 255)); // blue

        private static bool GetSheetRange(Worksheet sheet, out int lastUsedRow, out int lastUsedColumn)
        {
            try
            {
                Range last = sheet.Cells.SpecialCells(XlCellType.xlCellTypeLastCell, Type.Missing);
                Range range = sheet.get_Range("A1", last);

                lastUsedRow = last.Row;
                lastUsedColumn = last.Column;
                return true;
            }
            catch(Exception)
            {
                lastUsedColumn = 0;
                lastUsedRow = 0;
                return false;
            }
        }

        public static string Compare(string sourcePath, string targetPath, out string errorMessage)
        {
            string fileName = Path.GetTempPath() + Guid.NewGuid().ToString() + ".xlsx";
            errorMessage = "";
            int counter = 0;

            try
            {
                File.Copy(targetPath, fileName);
                ExcelReader source = new ExcelReader(sourcePath);
                ExcelReader comparison = new ExcelReader(fileName, false);

                /*
                // loop through named cells
                foreach (string name in comparison.NameDict.Keys)
                {
                    if (!source.NameDict.ContainsKey(name)) continue;
                    string sourceText = source.ReadText(name);
                    string targetText = comparison.ReadText(name);

                    if (sourceText == null)
                    {
                        if (targetText != null)
                        {
                            comparison.Colorize(name, diffColor);
                            counter++;
                        }
                    }
                    else if (targetText == null)
                    {
                        if (sourceText != null)
                        {
                            comparison.Colorize(name, diffColor);
                            counter++;
                        }
                    }
                    else if ((sourceText != null) && (targetText != null))
                    {
                        if (!sourceText.Equals(targetText))
                        {
                            // turn cell blue
                            comparison.Colorize(name, diffColor);
                            counter++;
                        }
                    }
                }
                */


                comparison.Save(fileName);
                errorMessage = string.Format("{0} differences found", counter);
            }
            catch (Exception ex)
            {
                errorMessage = ex.Message;
            }

            return fileName;
        }

    }
}