// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)

using System;
using System.IO;
using System.Text;

namespace ICSharpCode.Core
{
	/// <summary>
	/// A minimal version of FileUtility. Is used by ICSharpCode.SharpDevelop.Dom (which doesn't reference
	/// ICSharpCode.Core)
	/// </summary>
	static partial class FileUtility
	{
		/// <summary>
		/// Gets the normalized version of fileName.
		/// Slashes are replaced with backslashes, backreferences "." and ".." are 'evaluated'.
		/// </summary>
		public static string NormalizePath(string fileName)
		{
			if (string.IsNullOrEmpty(fileName)) return fileName;
			
			int i;
			
			bool isWeb = false;
			for (i = 0; i < fileName.Length; i++) {
				if (fileName[i] == '/' || fileName[i] == '\\')
					break;
				if (fileName[i] == ':') {
					if (i > 1)
						isWeb = true;
					break;
				}
			}
			
			char outputSeparator = isWeb ? '/' : System.IO.Path.DirectorySeparatorChar;
			
			StringBuilder result = new StringBuilder();
			if (isWeb == false && fileName.StartsWith(@"\\") || fileName.StartsWith("//")) {
				i = 2;
				result.Append(outputSeparator);
			} else {
				i = 0;
			}
			int segmentStartPos = i;
			for (; i <= fileName.Length; i++) {
				if (i == fileName.Length || fileName[i] == '/' || fileName[i] == '\\') {
					int segmentLength = i - segmentStartPos;
					switch (segmentLength) {
						case 0:
							// ignore empty segment (if not in web mode)
							// On unix, don't ignore empty segment if i==0
							if (isWeb || (i == 0 && Environment.OSVersion.Platform == PlatformID.Unix)) {
								result.Append(outputSeparator);
							}
							break;
						case 1:
							// ignore /./ segment, but append other one-letter segments
							if (fileName[segmentStartPos] != '.') {
								if (result.Length > 0) result.Append(outputSeparator);
								result.Append(fileName[segmentStartPos]);
							}
							break;
						case 2:
							if (fileName[segmentStartPos] == '.' && fileName[segmentStartPos + 1] == '.') {
								// remove previous segment
								int j;
								for (j = result.Length - 1; j >= 0 && result[j] != outputSeparator; j--);
								if (j > 0) {
									result.Length = j;
								}
								break;
							} else {
								// append normal segment
								goto default;
							}
						default:
							if (result.Length > 0) result.Append(outputSeparator);
							result.Append(fileName, segmentStartPos, segmentLength);
							break;
					}
					segmentStartPos = i + 1; // remember start position for next segment
				}
			}
			if (isWeb == false) {
				if (result.Length > 0 && result[result.Length - 1] == outputSeparator) {
					result.Length -= 1;
				}
				if (result.Length == 2 && result[1] == ':') {
					result.Append(outputSeparator);
				}
			}
			return result.ToString();
		}
		
		public static bool IsEqualFileName(string fileName1, string fileName2)
		{
			return string.Equals(NormalizePath(fileName1),
			                     NormalizePath(fileName2),
			                     StringComparison.OrdinalIgnoreCase);
		}
		
		public static bool IsBaseDirectory(string baseDirectory, string testDirectory)
		{
			if (baseDirectory == null || testDirectory == null)
				return false;
			baseDirectory = NormalizePath(baseDirectory) + Path.DirectorySeparatorChar;
			testDirectory = NormalizePath(testDirectory) + Path.DirectorySeparatorChar;
			
			return testDirectory.StartsWith(baseDirectory, StringComparison.OrdinalIgnoreCase);
		}
	}
}