/**** Requires PeHeaderReader to determine bitness: http://code.cheesydesign.com/?p=572 ****/

using Microsoft.Win32;
using System;
using System.Collections.Generic;
using System.IO;
using System.Security.AccessControl;

/// <summary>
/// See: http://support.microsoft.com/kb/240794
/// </summary>
public class ExcelHelper
{
	public enum ExcelVersions
	{
		/*
			Office 97   -  7.0
			Office 98   -  8.0
			Office 2000 -  9.0
			Office XP   - 10.0
			Office 2003 - 11.0
			Office 2007 - 12.0
			Office 2010 - 14.0 (sic!)
			Office 2013 - 15.0
		*/
		Excel_Pre2003 = 0,
		Excel_2003 = 11,
		Excel_2007 = 12,
		Excel_2010 = 14,
		Excel_2013 = 15,
		Excel_2016 = 16,
		Unknown = 99
	}

	private ExcelVersions Version = ExcelVersions.Unknown;

	public ExcelHelper(ExcelVersions version)
	{
		Version = version;
	}

	public string ExcelFilePath
	{
		get
		{
			var versionNumber = (int)Version;
			var keyPath = string.Format(@"Software\Microsoft\Office\{0}.0\Excel\InstallRoot", versionNumber);
			RegistryKey hklmWow32 = RegistryKey.OpenBaseKey(Microsoft.Win32.RegistryHive.LocalMachine, RegistryView.Registry32);
			RegistryKey key = hklmWow32.OpenSubKey(keyPath, RegistryKeyPermissionCheck.ReadSubTree, RegistryRights.ReadKey);

			if (key != null)
			{
				var path = key.GetValue("Path");

				if (path != null)
				{
					path = Path.Combine(path.ToString(), "excel.exe");
					if (File.Exists(path.ToString()))
						return path.ToString();
					else
						throw new Exception("Excel path specified in Registry not found on disk: " + path);
				}
				throw new Exception("InstallRoot key doesn't contain Path sub-key");
			}
			hklmWow32 = RegistryKey.OpenBaseKey(Microsoft.Win32.RegistryHive.LocalMachine, RegistryView.Registry64);
			key = hklmWow32.OpenSubKey(keyPath, RegistryKeyPermissionCheck.ReadSubTree, RegistryRights.ReadKey);

			if (key != null)
			{
				var path = key.GetValue("Path");

				if (path != null)
				{
					path = Path.Combine(path.ToString(), "excel.exe");
					if (File.Exists(path.ToString()))
						return path.ToString();
					else
						throw new Exception("Excel path specified in Registry not found on disk: " + path);
				}
				throw new Exception("InstallRoot key doesn't contain Path sub-key");
			}
			throw new Exception("Excel file path (InstallRoot key) not found");
		}
	}

	public bool ExcelIs32bit
	{
		get
		{
			var file = ExcelFilePath;

			if (string.IsNullOrWhiteSpace(file))
				throw new Exception("Excel path could not be determined.");

			if (!File.Exists(file))
				throw new Exception("Excel path is incorrect.");

			PeHeaderReader pe = new PeHeaderReader(file);
			return pe.Is32BitHeader;
		}
	}

	public ExcelVersions ExcelVersion
	{
		get { return Version; }
	}

	internal int ExcelVersionNumber
	{
		get { return (int)Version; }
	}

	public static string ExcelFullName(ExcelVersions version, bool is32bit)
	{
		var fullName = "";

		if (version == ExcelVersions.Excel_2003) fullName = "Excel 2003";
		else if (version == ExcelVersions.Excel_2007) fullName = "Excel 2007";
		else if (version == ExcelVersions.Excel_2010) fullName = "Excel 2010";
		else if (version == ExcelVersions.Excel_2013) fullName = "Excel 2013";
		else if (version == ExcelVersions.Excel_2016) fullName = "Excel 2016";
		else if (version == ExcelVersions.Excel_Pre2003) fullName = "(NOT SUPPORTED): Excel pre-2003";

		fullName += is32bit ? " (32bit)" : " (64bit)";
		return fullName;
	}

	public static List<ExcelVersions> GetAllInstalledVersionsOfExcel()
	{
		var results = new List<ExcelVersions>();

		if (ExcelVersionIsInstalled(ExcelVersions.Excel_2003)) results.Add(ExcelVersions.Excel_2003);
		if (ExcelVersionIsInstalled(ExcelVersions.Excel_2007)) results.Add(ExcelVersions.Excel_2007);
		if (ExcelVersionIsInstalled(ExcelVersions.Excel_2010)) results.Add(ExcelVersions.Excel_2010);
		if (ExcelVersionIsInstalled(ExcelVersions.Excel_2013)) results.Add(ExcelVersions.Excel_2013);
		if (ExcelVersionIsInstalled(ExcelVersions.Excel_2016)) results.Add(ExcelVersions.Excel_2016);

		return results;
	}

	private static bool ExcelVersionIsInstalled(ExcelVersions version)
	{
		var versionNumber = (int)version;
		var keyPath = string.Format(@"Software\Microsoft\Office\{0}.0\Excel\InstallRoot", versionNumber);
		RegistryKey hklmWow32 = RegistryKey.OpenBaseKey(Microsoft.Win32.RegistryHive.LocalMachine, RegistryView.Registry32);
		RegistryKey key = hklmWow32.OpenSubKey(keyPath, RegistryKeyPermissionCheck.ReadSubTree, RegistryRights.ReadKey);

		if (key != null)
		{
			var path = key.GetValue("Path");

			if (path != null)
			{
				path = Path.Combine(path.ToString(), "excel.exe");
				return File.Exists(path.ToString());
			}
		}
		////////////////
		hklmWow32 = RegistryKey.OpenBaseKey(Microsoft.Win32.RegistryHive.LocalMachine, RegistryView.Registry64);
		key = hklmWow32.OpenSubKey(keyPath, RegistryKeyPermissionCheck.ReadSubTree, RegistryRights.ReadKey);

		if (key != null)
		{
			var path = key.GetValue("Path");

			if (path != null)
			{
				path = Path.Combine(path.ToString(), "excel.exe");
				return File.Exists(path.ToString());
			}
		}
		return false;
	}

}