/**
 * Namespace: System.Web.UI.Utils
 * Class:     UrlUtils
 * 
 * Author:  Gaurav Vaish
 * Maintainer: gvaish@iitk.ac.in
 * Status:  ??%
 * 
 * (C) Gaurav Vaish (2001)
 */

using System;
using System.Collections;
using System.Text;

namespace System.Web.Utils
{
	internal class UrlUtils
	{
		/*
		 * I could not find these functions in the class System.Uri
		 * Besides, an instance of Uri will not be formed until and unless the address is of
		 * the form protocol://[user:pass]host[:port]/[fullpath]
		 * ie, a protocol, and that too without any blanks before,
		 * is a must which may not be the case here.
		 * Important: Escaped URL is assumed here. nothing like .aspx?path=/something
		 * It should be .aspx?path=%2Fsomething
		 */
		public static string GetProtocol(string url)
		{
			//Taking code from Java Class java.net.URL
			if(url!=null)
			{
				if(url.Length>0)
				{
					
					int i, start = 0, limit;
					limit = url.Length;
					char c;
					bool aRef = false;
					while( (limit > 0) && (url[limit-1] <= ' '))
					{
						limit --;
					}
					while( (start < limit) && (url[start] <= ' '))
					{
						start++;
					}
					if(RegionMatches(true, url, start, "url:", 0, 4))
					{
						start += 4;
					}
					if(start < url.Length && url[start]=='#')
					{
						aRef = true;
					}
					for(i = start; !aRef && (i < limit) && ((c=url[i]) != '/'); i++)
					{
						if(c==':')
						{
							return url.Substring(start, i - start);
						}
					}
				}
			}
			return String.Empty;
		}
		
		public static bool IsRelativeUrl(string url)
		{
			if(url.IndexOf(':') != -1)
				return !IsRootUrl(url);
			return true;
		}

		public static bool IsRootUrl(string url)
		{
			if(url!=null)
			{
				if(url.Length>0)
				{
					return IsValidProtocol(GetProtocol(url).ToLower());
				}
			}
			return true;
		}
		
		public static bool IsRooted(string path)
		{
			if(path!=null && path.Length > 0)
			{
				return (path[0]=='/' || path[0]=='\\');
			}
			return false;
		}
		
		public static void FailIfPhysicalPath(string path)
		{
			if(path!= null && path.Length > 0)
			{
				if(path[0]==':' || path.StartsWith(@"\\"))
					throw new HttpException(HttpRuntime.FormatResourceString("Physical_path_not_allowed", path));
			}
		}
		
		public static string Combine(string basePath, string relPath)
		{
			FailIfPhysicalPath(relPath);
			if(IsRootUrl(relPath))
			{
				if(relPath != null && relPath.Length > 0)
				{
					return Reduce(relPath);
				}
				return String.Empty;
			}
			if(relPath.Length < 3 || relPath[0]!='~' || (relPath[0]!='/' && relPath[0]!='\\'))
			{
				if(basePath==null || basePath.Length==1 || basePath[0]=='/')
					basePath = String.Empty;
				return Reduce(basePath + "/" + relPath);
			}
			string vPath = HttpRuntime.AppDomainAppVirtualPath;
			if(vPath.Length <= 1)
				vPath = String.Empty;
			return Reduce(vPath + "/" + relPath.Substring(2));
		}
		
		public static bool IsValidProtocol(string protocol)
		{
			if(protocol.Length < 1)
				return false;
			char c = protocol[0];
			if(!Char.IsLetter(c))
			{
				return false;
			}
			for(int i=1; i < protocol.Length; i++)
			{
				c = protocol[i];
				if(!Char.IsLetterOrDigit(c) && c!='.' && c!='+' && c!='-')
				{
					return false;
				}
			}
			return true;
		}
		
		/*
		 * MakeRelative("http://www.foo.com/bar1/bar2/file","http://www.foo.com/bar1")
		 * will return "bar2/file"
		 * while MakeRelative("http://www.foo.com/bar1/...","http://www.anotherfoo.com")
		 * return 'null' and so does the call
		 * MakeRelative("http://www.foo.com/bar1/bar2","http://www.foo.com/bar")
		 */
		public static string MakeRelative(string fullUrl, string relativeTo)
		{
			if(fullUrl==relativeTo)
			{
				return String.Empty;
			}
			if(fullUrl.IndexOf(relativeTo)!=0)
			{
				return null;
			}
			string leftOver = fullUrl.Substring(relativeTo.Length);
			if(!fullUrl.EndsWith("/") && !leftOver.StartsWith("/"))
			{
				return null;
			}
			if(leftOver.StartsWith("/"))
			{
				leftOver = leftOver.Substring(1);
			}
			return leftOver;
		}
		
		/*
		 * Check JavaDocs for java.lang.String#RegionMatches(bool, int, String, int, int)
		 * Could not find anything similar in the System.String class
		 */
		public static bool RegionMatches(bool ignoreCase, string source, int start, string match, int offset, int len)
		{
			if(source!=null || match!=null)
			{
				if(source.Length>0 && match.Length>0)
				{
					char[] ta = source.ToCharArray();
					char[] pa = match.ToCharArray();
					if((offset < 0) || (start < 0) || (start > (source.Length - len)) || (offset > (match.Length - len)))
					{
						return false;
					}
					while(len-- > 0)
					{
						char c1 = ta[start++];
						char c2 = pa[offset++];
						if(c1==c2)
							continue;
						if(ignoreCase)
						{
							if(Char.ToUpper(c1)==Char.ToUpper(c2))
								continue;
							// Check for Gregorian Calendar where the above may not hold good
							if(Char.ToLower(c1)==Char.ToLower(c2))
								continue;
						}
						return false;
					}
					return true;
				}
			}
			return false;
		}

		public static string Reduce(string path)
		{
			int len = path.Length;
			int dotIndex = -1;
			path = path.Replace('\\','/');
			while(true)
			{
				dotIndex++;
				dotIndex = path.IndexOf('.', dotIndex);
				if(dotIndex < 0)
				{
					return path;
				}
				if(dotIndex != 0 && path[dotIndex -1]=='/')
					continue;
				if(dotIndex+1 == len || path[dotIndex+1]=='/')
					break;
				if(path[dotIndex+1]=='.')
					continue;
				if(dotIndex+2 == len || path[dotIndex+2]=='/')
					break;
			}
			ArrayList list = new ArrayList();
			StringBuilder sb = new StringBuilder();
			dotIndex = 0;
			int temp;
			do
			{
				temp = dotIndex;
				dotIndex = path.IndexOf('/', temp + 1);
				if(dotIndex < 0)
					dotIndex = len;
				if( (dotIndex - temp) <= 3 && (dotIndex < 1 || path[dotIndex - 1]== '.') && ( (temp+1) >= len || path[temp+1]=='.') )
				{
					if(dotIndex - temp == 3)
						continue;
					if(list.Count == 0)
						throw new System.Web.HttpException(System.Web.HttpRuntime.FormatResourceString("Cannot_exit_up_top_directory"));
					sb.Length = (int) list[list.Count - 1];
					list.RemoveRange(list.Count - 1, 1);
					continue;
				}
				list.Add(sb.Length);
				sb.Append(path, temp, dotIndex - temp);
			} while(dotIndex != len);
			return sb.ToString();
		}
		
		public static string GetDirectory(string url)
		{
			if(url==null)
			{
				return null;
			}
			if(url.Length==0)
			{
				return String.Empty;
			}
			url.Replace('\\','/');
			string baseDir = url.Substring(0, url.LastIndexOf('/'));
			if(baseDir.Length==0)
			{
				baseDir = "/";
			}
			return baseDir;
		}
	}
}