/**
 * Namespace: System.Web.UI.Utils
 * Class:     UrlUtils
 * 
 * Author:  Gaurav Vaish
 * Contact: <gvaish@iitk.ac.in>
 * Status:  10??%
 * 
 * (C) Gaurav Vaish (2001)
 */

using System;

namespace System.Web.UI.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 IsRootUrl(string url)
		{
			if(url!=null)
			{
				if(url.Length>0)
				{
					return IsValidProtocol(GetProtocol(url).ToLower());
				}
			}
			return false;
		}
		
		public static bool IsValidProtocol(string protocol)
		{
			if(protocol.Length < 1)
				return false;
			char c = protocol[0];
			if(!Char.IsLetter(c))
			{
				System.Console.WriteLine("Character {0} is not a letter.", c);
				return false;
			}
			for(int i=1; i < protocol.Length; i++)
			{
				c = protocol[i];
				if(!Char.IsLetterOrDigit(c) && c!='.' && c!='+' && c!='-')
				{
					System.Console.WriteLine("Character \"{0}\" is not a letter or a digit or something.", 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)
		{
			//Uri fromUri;
			//Uri toUri;
			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 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;
		}
	}
}