// 
// System.Web.HttpUtility
// http://github.com/mono/mono/tree/master/mcs/class/System.Web/System.Web.Util/
//
// Authors:
//   Patrik Torstensson (Patrik.Torstensson@labs2.com)
//   Wictor Wilén (decode/encode functions) (wictor@ibizkit.se)
//   Tim Coleman (tim@timcoleman.com)
//   Gonzalo Paniagua Javier (gonzalo@ximian.com)
//
// Copyright (C) 2005 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System.Collections;
using System.Collections.Specialized;
using System.Globalization;
using System.IO;
using System.Security.Permissions;
using System.Text;
using System;
using System.Web;
using Google.GData.Client.Util;

#if NET_2_0
using System.Collections.Generic;
#endif

namespace Google.GData.Client.Util {
	class Helpers {
		public static readonly CultureInfo InvariantCulture = CultureInfo.InvariantCulture;
	}
}

namespace Google.GData.Client
{

#if !MONOTOUCH
	// CAS - no InheritanceDemand here as the class is sealed
	[AspNetHostingPermission(SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)]
#endif

	public sealed class HttpUtility {

		#region Fields

		static Hashtable entities;
		static object lock_ = new object();

		#endregion // Fields

		static Hashtable Entities {
			get {
				lock (lock_) {
					if (entities == null)
						InitEntities();

					return entities;
				}
			}
		}

		#region Constructors

		static void InitEntities() {
			// Build the hash table of HTML entity references.  This list comes
			// from the HTML 4.01 W3C recommendation.
			entities = new Hashtable();
			entities.Add("nbsp", '\u00A0');
			entities.Add("iexcl", '\u00A1');
			entities.Add("cent", '\u00A2');
			entities.Add("pound", '\u00A3');
			entities.Add("curren", '\u00A4');
			entities.Add("yen", '\u00A5');
			entities.Add("brvbar", '\u00A6');
			entities.Add("sect", '\u00A7');
			entities.Add("uml", '\u00A8');
			entities.Add("copy", '\u00A9');
			entities.Add("ordf", '\u00AA');
			entities.Add("laquo", '\u00AB');
			entities.Add("not", '\u00AC');
			entities.Add("shy", '\u00AD');
			entities.Add("reg", '\u00AE');
			entities.Add("macr", '\u00AF');
			entities.Add("deg", '\u00B0');
			entities.Add("plusmn", '\u00B1');
			entities.Add("sup2", '\u00B2');
			entities.Add("sup3", '\u00B3');
			entities.Add("acute", '\u00B4');
			entities.Add("micro", '\u00B5');
			entities.Add("para", '\u00B6');
			entities.Add("middot", '\u00B7');
			entities.Add("cedil", '\u00B8');
			entities.Add("sup1", '\u00B9');
			entities.Add("ordm", '\u00BA');
			entities.Add("raquo", '\u00BB');
			entities.Add("frac14", '\u00BC');
			entities.Add("frac12", '\u00BD');
			entities.Add("frac34", '\u00BE');
			entities.Add("iquest", '\u00BF');
			entities.Add("Agrave", '\u00C0');
			entities.Add("Aacute", '\u00C1');
			entities.Add("Acirc", '\u00C2');
			entities.Add("Atilde", '\u00C3');
			entities.Add("Auml", '\u00C4');
			entities.Add("Aring", '\u00C5');
			entities.Add("AElig", '\u00C6');
			entities.Add("Ccedil", '\u00C7');
			entities.Add("Egrave", '\u00C8');
			entities.Add("Eacute", '\u00C9');
			entities.Add("Ecirc", '\u00CA');
			entities.Add("Euml", '\u00CB');
			entities.Add("Igrave", '\u00CC');
			entities.Add("Iacute", '\u00CD');
			entities.Add("Icirc", '\u00CE');
			entities.Add("Iuml", '\u00CF');
			entities.Add("ETH", '\u00D0');
			entities.Add("Ntilde", '\u00D1');
			entities.Add("Ograve", '\u00D2');
			entities.Add("Oacute", '\u00D3');
			entities.Add("Ocirc", '\u00D4');
			entities.Add("Otilde", '\u00D5');
			entities.Add("Ouml", '\u00D6');
			entities.Add("times", '\u00D7');
			entities.Add("Oslash", '\u00D8');
			entities.Add("Ugrave", '\u00D9');
			entities.Add("Uacute", '\u00DA');
			entities.Add("Ucirc", '\u00DB');
			entities.Add("Uuml", '\u00DC');
			entities.Add("Yacute", '\u00DD');
			entities.Add("THORN", '\u00DE');
			entities.Add("szlig", '\u00DF');
			entities.Add("agrave", '\u00E0');
			entities.Add("aacute", '\u00E1');
			entities.Add("acirc", '\u00E2');
			entities.Add("atilde", '\u00E3');
			entities.Add("auml", '\u00E4');
			entities.Add("aring", '\u00E5');
			entities.Add("aelig", '\u00E6');
			entities.Add("ccedil", '\u00E7');
			entities.Add("egrave", '\u00E8');
			entities.Add("eacute", '\u00E9');
			entities.Add("ecirc", '\u00EA');
			entities.Add("euml", '\u00EB');
			entities.Add("igrave", '\u00EC');
			entities.Add("iacute", '\u00ED');
			entities.Add("icirc", '\u00EE');
			entities.Add("iuml", '\u00EF');
			entities.Add("eth", '\u00F0');
			entities.Add("ntilde", '\u00F1');
			entities.Add("ograve", '\u00F2');
			entities.Add("oacute", '\u00F3');
			entities.Add("ocirc", '\u00F4');
			entities.Add("otilde", '\u00F5');
			entities.Add("ouml", '\u00F6');
			entities.Add("divide", '\u00F7');
			entities.Add("oslash", '\u00F8');
			entities.Add("ugrave", '\u00F9');
			entities.Add("uacute", '\u00FA');
			entities.Add("ucirc", '\u00FB');
			entities.Add("uuml", '\u00FC');
			entities.Add("yacute", '\u00FD');
			entities.Add("thorn", '\u00FE');
			entities.Add("yuml", '\u00FF');
			entities.Add("fnof", '\u0192');
			entities.Add("Alpha", '\u0391');
			entities.Add("Beta", '\u0392');
			entities.Add("Gamma", '\u0393');
			entities.Add("Delta", '\u0394');
			entities.Add("Epsilon", '\u0395');
			entities.Add("Zeta", '\u0396');
			entities.Add("Eta", '\u0397');
			entities.Add("Theta", '\u0398');
			entities.Add("Iota", '\u0399');
			entities.Add("Kappa", '\u039A');
			entities.Add("Lambda", '\u039B');
			entities.Add("Mu", '\u039C');
			entities.Add("Nu", '\u039D');
			entities.Add("Xi", '\u039E');
			entities.Add("Omicron", '\u039F');
			entities.Add("Pi", '\u03A0');
			entities.Add("Rho", '\u03A1');
			entities.Add("Sigma", '\u03A3');
			entities.Add("Tau", '\u03A4');
			entities.Add("Upsilon", '\u03A5');
			entities.Add("Phi", '\u03A6');
			entities.Add("Chi", '\u03A7');
			entities.Add("Psi", '\u03A8');
			entities.Add("Omega", '\u03A9');
			entities.Add("alpha", '\u03B1');
			entities.Add("beta", '\u03B2');
			entities.Add("gamma", '\u03B3');
			entities.Add("delta", '\u03B4');
			entities.Add("epsilon", '\u03B5');
			entities.Add("zeta", '\u03B6');
			entities.Add("eta", '\u03B7');
			entities.Add("theta", '\u03B8');
			entities.Add("iota", '\u03B9');
			entities.Add("kappa", '\u03BA');
			entities.Add("lambda", '\u03BB');
			entities.Add("mu", '\u03BC');
			entities.Add("nu", '\u03BD');
			entities.Add("xi", '\u03BE');
			entities.Add("omicron", '\u03BF');
			entities.Add("pi", '\u03C0');
			entities.Add("rho", '\u03C1');
			entities.Add("sigmaf", '\u03C2');
			entities.Add("sigma", '\u03C3');
			entities.Add("tau", '\u03C4');
			entities.Add("upsilon", '\u03C5');
			entities.Add("phi", '\u03C6');
			entities.Add("chi", '\u03C7');
			entities.Add("psi", '\u03C8');
			entities.Add("omega", '\u03C9');
			entities.Add("thetasym", '\u03D1');
			entities.Add("upsih", '\u03D2');
			entities.Add("piv", '\u03D6');
			entities.Add("bull", '\u2022');
			entities.Add("hellip", '\u2026');
			entities.Add("prime", '\u2032');
			entities.Add("Prime", '\u2033');
			entities.Add("oline", '\u203E');
			entities.Add("frasl", '\u2044');
			entities.Add("weierp", '\u2118');
			entities.Add("image", '\u2111');
			entities.Add("real", '\u211C');
			entities.Add("trade", '\u2122');
			entities.Add("alefsym", '\u2135');
			entities.Add("larr", '\u2190');
			entities.Add("uarr", '\u2191');
			entities.Add("rarr", '\u2192');
			entities.Add("darr", '\u2193');
			entities.Add("harr", '\u2194');
			entities.Add("crarr", '\u21B5');
			entities.Add("lArr", '\u21D0');
			entities.Add("uArr", '\u21D1');
			entities.Add("rArr", '\u21D2');
			entities.Add("dArr", '\u21D3');
			entities.Add("hArr", '\u21D4');
			entities.Add("forall", '\u2200');
			entities.Add("part", '\u2202');
			entities.Add("exist", '\u2203');
			entities.Add("empty", '\u2205');
			entities.Add("nabla", '\u2207');
			entities.Add("isin", '\u2208');
			entities.Add("notin", '\u2209');
			entities.Add("ni", '\u220B');
			entities.Add("prod", '\u220F');
			entities.Add("sum", '\u2211');
			entities.Add("minus", '\u2212');
			entities.Add("lowast", '\u2217');
			entities.Add("radic", '\u221A');
			entities.Add("prop", '\u221D');
			entities.Add("infin", '\u221E');
			entities.Add("ang", '\u2220');
			entities.Add("and", '\u2227');
			entities.Add("or", '\u2228');
			entities.Add("cap", '\u2229');
			entities.Add("cup", '\u222A');
			entities.Add("int", '\u222B');
			entities.Add("there4", '\u2234');
			entities.Add("sim", '\u223C');
			entities.Add("cong", '\u2245');
			entities.Add("asymp", '\u2248');
			entities.Add("ne", '\u2260');
			entities.Add("equiv", '\u2261');
			entities.Add("le", '\u2264');
			entities.Add("ge", '\u2265');
			entities.Add("sub", '\u2282');
			entities.Add("sup", '\u2283');
			entities.Add("nsub", '\u2284');
			entities.Add("sube", '\u2286');
			entities.Add("supe", '\u2287');
			entities.Add("oplus", '\u2295');
			entities.Add("otimes", '\u2297');
			entities.Add("perp", '\u22A5');
			entities.Add("sdot", '\u22C5');
			entities.Add("lceil", '\u2308');
			entities.Add("rceil", '\u2309');
			entities.Add("lfloor", '\u230A');
			entities.Add("rfloor", '\u230B');
			entities.Add("lang", '\u2329');
			entities.Add("rang", '\u232A');
			entities.Add("loz", '\u25CA');
			entities.Add("spades", '\u2660');
			entities.Add("clubs", '\u2663');
			entities.Add("hearts", '\u2665');
			entities.Add("diams", '\u2666');
			entities.Add("quot", '\u0022');
			entities.Add("amp", '\u0026');
			entities.Add("lt", '\u003C');
			entities.Add("gt", '\u003E');
			entities.Add("OElig", '\u0152');
			entities.Add("oelig", '\u0153');
			entities.Add("Scaron", '\u0160');
			entities.Add("scaron", '\u0161');
			entities.Add("Yuml", '\u0178');
			entities.Add("circ", '\u02C6');
			entities.Add("tilde", '\u02DC');
			entities.Add("ensp", '\u2002');
			entities.Add("emsp", '\u2003');
			entities.Add("thinsp", '\u2009');
			entities.Add("zwnj", '\u200C');
			entities.Add("zwj", '\u200D');
			entities.Add("lrm", '\u200E');
			entities.Add("rlm", '\u200F');
			entities.Add("ndash", '\u2013');
			entities.Add("mdash", '\u2014');
			entities.Add("lsquo", '\u2018');
			entities.Add("rsquo", '\u2019');
			entities.Add("sbquo", '\u201A');
			entities.Add("ldquo", '\u201C');
			entities.Add("rdquo", '\u201D');
			entities.Add("bdquo", '\u201E');
			entities.Add("dagger", '\u2020');
			entities.Add("Dagger", '\u2021');
			entities.Add("permil", '\u2030');
			entities.Add("lsaquo", '\u2039');
			entities.Add("rsaquo", '\u203A');
			entities.Add("euro", '\u20AC');
		}

		public HttpUtility() {
		}

		#endregion // Constructors

		#region Methods

		public static void HtmlAttributeEncode(string s, TextWriter output) {
			output.Write(HtmlAttributeEncode(s));
		}

		public static string HtmlAttributeEncode(string s) {
			if (null == s) {
				return null;
			}

			bool needEncode = false;
			for (int i = 0; i < s.Length; i++) {
				if (s[i] == '&' || s[i] == '"' || s[i] == '<') {
					needEncode = true;
					break;
				}
			}

			if (!needEncode) {
				return s;
			}

			StringBuilder output = new StringBuilder();
			int len = s.Length;
			for (int i = 0; i < len; i++) {
				switch (s[i]) {
					case '&':
						output.Append("&amp;");
						break;
					case '"':
						output.Append("&quot;");
						break;
					case '<':
						output.Append("&lt;");
						break;
					default:
						output.Append(s[i]);
						break;
				}
			}

			return output.ToString();
		}

		public static string UrlDecode(string str) {
			return UrlDecode(str, Encoding.UTF8);
		}

		static char[] GetChars(MemoryStream b, Encoding e) {
			return e.GetChars(b.GetBuffer(), 0, (int)b.Length);
		}

		static void WriteCharBytes(IList buf, char ch, Encoding e) {
			if (ch > 255) {
				foreach (byte b in e.GetBytes(new char[] { ch }))
					buf.Add(b);
			} else
				buf.Add((byte)ch);
		}

		public static string UrlDecode(string s, Encoding e) {
			if (null == s)
				return null;

			if (s.IndexOf('%') == -1 && s.IndexOf('+') == -1)
				return s;

			if (e == null)
				e = Encoding.UTF8;

			long len = s.Length;
#if NET_2_0
            var bytes = new List <byte>();
#else
			ArrayList bytes = new ArrayList();
#endif
			int xchar;
			char ch;

			for (int i = 0; i < len; i++) {
				ch = s[i];
				if (ch == '%' && i + 2 < len && s[i + 1] != '%') {
					if (s[i + 1] == 'u' && i + 5 < len) {
						// unicode hex sequence
						xchar = GetChar(s, i + 2, 4);
						if (xchar != -1) {
							WriteCharBytes(bytes, (char)xchar, e);
							i += 5;
						} else {
							WriteCharBytes(bytes, '%', e);
						}
					} else if ((xchar = GetChar(s, i + 1, 2)) != -1) {
						WriteCharBytes(bytes, (char)xchar, e);
						i += 2;
					} else {
						WriteCharBytes(bytes, '%', e);
					}
					continue;
				}

				if (ch == '+')
					WriteCharBytes(bytes, ' ', e);
				else
					WriteCharBytes(bytes, ch, e);
			}

#if NET_2_0
            byte[] buf = bytes.ToArray ();
#else
			byte[] buf = (byte[])bytes.ToArray(typeof(byte));
#endif

			bytes = null;
            return e.GetString(buf);
        }

		public static string UrlDecode(byte[] bytes, Encoding e) {
			if (bytes == null)
				return null;

			return UrlDecode(bytes, 0, bytes.Length, e);
		}

		static int GetInt(byte b) {
			char c = (char)b;
			if (c >= '0' && c <= '9')
				return c - '0';

			if (c >= 'a' && c <= 'f')
				return c - 'a' + 10;

			if (c >= 'A' && c <= 'F')
				return c - 'A' + 10;

			return -1;
		}

		static int GetChar(byte[] bytes, int offset, int length) {
			int value = 0;
			int end = length + offset;
			for (int i = offset; i < end; i++) {
				int current = GetInt(bytes[i]);
				if (current == -1)
					return -1;
				value = (value << 4) + current;
			}

			return value;
		}

		static int GetChar(string str, int offset, int length) {
			int val = 0;
			int end = length + offset;
			for (int i = offset; i < end; i++) {
				char c = str[i];
				if (c > 127)
					return -1;

				int current = GetInt((byte)c);
				if (current == -1)
					return -1;
				val = (val << 4) + current;
			}

			return val;
		}

		public static string UrlDecode(byte[] bytes, int offset, int count, Encoding e) {
			if (bytes == null)
				return null;
			if (count == 0)
				return String.Empty;

			if (bytes == null)
				throw new ArgumentNullException("bytes");

			if (offset < 0 || offset > bytes.Length)
				throw new ArgumentOutOfRangeException("offset");

			if (count < 0 || offset + count > bytes.Length)
				throw new ArgumentOutOfRangeException("count");

			StringBuilder output = new StringBuilder();
			MemoryStream acc = new MemoryStream();

			int end = count + offset;
			int xchar;
			for (int i = offset; i < end; i++) {
				if (bytes[i] == '%' && i + 2 < count && bytes[i + 1] != '%') {
					if (bytes[i + 1] == (byte)'u' && i + 5 < end) {
						if (acc.Length > 0) {
							output.Append(GetChars(acc, e));
							acc.SetLength(0);
						}
						xchar = GetChar(bytes, i + 2, 4);
						if (xchar != -1) {
							output.Append((char)xchar);
							i += 5;
							continue;
						}
					} else if ((xchar = GetChar(bytes, i + 1, 2)) != -1) {
						acc.WriteByte((byte)xchar);
						i += 2;
						continue;
					}
				}

				if (acc.Length > 0) {
					output.Append(GetChars(acc, e));
					acc.SetLength(0);
				}

				if (bytes[i] == '+') {
					output.Append(' ');
				} else {
					output.Append((char)bytes[i]);
				}
			}

			if (acc.Length > 0) {
				output.Append(GetChars(acc, e));
			}

			acc = null;
			return output.ToString();
		}

		public static byte[] UrlDecodeToBytes(byte[] bytes) {
			if (bytes == null)
				return null;

			return UrlDecodeToBytes(bytes, 0, bytes.Length);
		}

		public static byte[] UrlDecodeToBytes(string str) {
			return UrlDecodeToBytes(str, Encoding.UTF8);
		}

		public static byte[] UrlDecodeToBytes(string str, Encoding e) {
			if (str == null)
				return null;

			if (e == null)
				throw new ArgumentNullException("e");

			return UrlDecodeToBytes(e.GetBytes(str));
		}

		public static byte[] UrlDecodeToBytes(byte[] bytes, int offset, int count) {
			if (bytes == null)
				return null;
			if (count == 0)
				return new byte[0];

			int len = bytes.Length;
			if (offset < 0 || offset >= len)
				throw new ArgumentOutOfRangeException("offset");

			if (count < 0 || offset > len - count)
				throw new ArgumentOutOfRangeException("count");

			MemoryStream result = new MemoryStream();
			int end = offset + count;
			for (int i = offset; i < end; i++) {
				char c = (char)bytes[i];
				if (c == '+') {
					c = ' ';
				} else if (c == '%' && i < end - 2) {
					int xchar = GetChar(bytes, i + 1, 2);
					if (xchar != -1) {
						c = (char)xchar;
						i += 2;
					}
				}
				result.WriteByte((byte)c);
			}

			return result.ToArray();
		}

		public static string UrlEncode(string str) {
			return UrlEncode(str, Encoding.UTF8);
		}

		public static string UrlEncode(string s, Encoding Enc) {
			if (s == null)
				return null;

			if (s == "")
				return "";

			bool needEncode = false;
			int len = s.Length;
			for (int i = 0; i < len; i++) {
				char c = s[i];
				if ((c < '0') || (c < 'A' && c > '9') || (c > 'Z' && c < 'a') || (c > 'z')) {
					if (NotEncoded(c))
						continue;

					needEncode = true;
					break;
				}
			}

			if (!needEncode)
				return s;

			// avoided GetByteCount call
			byte[] bytes = new byte[Enc.GetMaxByteCount(s.Length)];
			int realLen = Enc.GetBytes(s, 0, s.Length, bytes, 0);
            return Encoding.ASCII.GetString(UrlEncodeToBytes(bytes, 0, realLen));
        }

		public static string UrlEncode(byte[] bytes) {
			if (bytes == null)
				return null;

			if (bytes.Length == 0)
				return "";

            return Encoding.ASCII.GetString(UrlEncodeToBytes(bytes, 0, bytes.Length));
        }

		public static string UrlEncode(byte[] bytes, int offset, int count) {
			if (bytes == null)
				return null;

			if (bytes.Length == 0)
				return "";

            return Encoding.ASCII.GetString(UrlEncodeToBytes(bytes, offset, count));
        }

		public static byte[] UrlEncodeToBytes(string str) {
			return UrlEncodeToBytes(str, Encoding.UTF8);
		}

		public static byte[] UrlEncodeToBytes(string str, Encoding e) {
			if (str == null)
				return null;

			if (str == "")
				return new byte[0];

			byte[] bytes = e.GetBytes(str);
			return UrlEncodeToBytes(bytes, 0, bytes.Length);
		}

		public static byte[] UrlEncodeToBytes(byte[] bytes) {
			if (bytes == null)
				return null;

			if (bytes.Length == 0)
				return new byte[0];

			return UrlEncodeToBytes(bytes, 0, bytes.Length);
		}

		static char[] hexChars = "0123456789abcdef".ToCharArray();

		static bool NotEncoded(char c) {
			return (c == '!' || c == '\'' || c == '(' || c == ')' || c == '*' || c == '-' || c == '.' || c == '_');
		}

		static void UrlEncodeChar(char c, Stream result, bool isUnicode) {
			if (c > 255) {
				//FIXME: what happens when there is an internal error?
				//if (!isUnicode)
				//	throw new ArgumentOutOfRangeException ("c", c, "c must be less than 256");
				int idx;
				int i = (int)c;

				result.WriteByte((byte)'%');
				result.WriteByte((byte)'u');
				idx = i >> 12;
				result.WriteByte((byte)hexChars[idx]);
				idx = (i >> 8) & 0x0F;
				result.WriteByte((byte)hexChars[idx]);
				idx = (i >> 4) & 0x0F;
				result.WriteByte((byte)hexChars[idx]);
				idx = i & 0x0F;
				result.WriteByte((byte)hexChars[idx]);
				return;
			}

			if (c > ' ' && NotEncoded(c)) {
				result.WriteByte((byte)c);
				return;
			}
			if (c == ' ') {
				result.WriteByte((byte)'+');
				return;
			}
			if ((c < '0') ||
				(c < 'A' && c > '9') ||
				(c > 'Z' && c < 'a') ||
				(c > 'z')) {
				if (isUnicode && c > 127) {
					result.WriteByte((byte)'%');
					result.WriteByte((byte)'u');
					result.WriteByte((byte)'0');
					result.WriteByte((byte)'0');
				} else
					result.WriteByte((byte)'%');

				int idx = ((int)c) >> 4;
				result.WriteByte((byte)hexChars[idx]);
				idx = ((int)c) & 0x0F;
				result.WriteByte((byte)hexChars[idx]);
			} else
				result.WriteByte((byte)c);
		}

		public static byte[] UrlEncodeToBytes(byte[] bytes, int offset, int count) {
			if (bytes == null)
				return null;

			int len = bytes.Length;
			if (len == 0)
				return new byte[0];

			if (offset < 0 || offset >= len)
				throw new ArgumentOutOfRangeException("offset");

			if (count < 0 || count > len - offset)
				throw new ArgumentOutOfRangeException("count");

			MemoryStream result = new MemoryStream(count);
			int end = offset + count;
			for (int i = offset; i < end; i++)
				UrlEncodeChar((char)bytes[i], result, false);

			return result.ToArray();
		}

		public static string UrlEncodeUnicode(string str) {
			if (str == null)
				return null;

            return Encoding.ASCII.GetString(UrlEncodeUnicodeToBytes(str));
        }

		public static byte[] UrlEncodeUnicodeToBytes(string str) {
			if (str == null)
				return null;

			if (str == "")
				return new byte[0];

			MemoryStream result = new MemoryStream(str.Length);
			foreach (char c in str) {
				UrlEncodeChar(c, result, true);
			}
			return result.ToArray();
		}

		/// <summary>
		/// Decodes an HTML-encoded string and returns the decoded string.
		/// </summary>
		/// <param name="s">The HTML string to decode. </param>
		/// <returns>The decoded text.</returns>
		public static string HtmlDecode(string s) {
			if (s == null)
				throw new ArgumentNullException("s");

			if (s.IndexOf('&') == -1)
				return s;

			StringBuilder entity = new StringBuilder();
			StringBuilder output = new StringBuilder();
			int len = s.Length;
			// 0 -> nothing,
			// 1 -> right after '&'
			// 2 -> between '&' and ';' but no '#'
			// 3 -> '#' found after '&' and getting numbers
			int state = 0;
			int number = 0;
			bool have_trailing_digits = false;

			for (int i = 0; i < len; i++) {
				char c = s[i];
				if (state == 0) {
					if (c == '&') {
						entity.Append(c);
						state = 1;
					} else {
						output.Append(c);
					}
					continue;
				}

				if (c == '&') {
					state = 1;
					if (have_trailing_digits) {
						entity.Append(number.ToString(Helpers.InvariantCulture));
						have_trailing_digits = false;
					}

					output.Append(entity.ToString());
					entity.Length = 0;
					entity.Append('&');
					continue;
				}

				if (state == 1) {
					if (c == ';') {
						state = 0;
						output.Append(entity.ToString());
						output.Append(c);
						entity.Length = 0;
					} else {
						number = 0;
						if (c != '#') {
							state = 2;
						} else {
							state = 3;
						}
						entity.Append(c);
					}
				} else if (state == 2) {
					entity.Append(c);
					if (c == ';') {
						string key = entity.ToString();
						if (key.Length > 1 && Entities.ContainsKey(key.Substring(1, key.Length - 2)))
							key = Entities[key.Substring(1, key.Length - 2)].ToString();

						output.Append(key);
						state = 0;
						entity.Length = 0;
					}
				} else if (state == 3) {
					if (c == ';') {
						if (number > 65535) {
							output.Append("&#");
							output.Append(number.ToString(Helpers.InvariantCulture));
							output.Append(";");
						} else {
							output.Append((char)number);
						}
						state = 0;
						entity.Length = 0;
						have_trailing_digits = false;
					} else if (Char.IsDigit(c)) {
						number = number * 10 + ((int)c - '0');
						have_trailing_digits = true;
					} else {
						state = 2;
						if (have_trailing_digits) {
							entity.Append(number.ToString(Helpers.InvariantCulture));
							have_trailing_digits = false;
						}
						entity.Append(c);
					}
				}
			}

			if (entity.Length > 0) {
				output.Append(entity.ToString());
			} else if (have_trailing_digits) {
				output.Append(number.ToString(Helpers.InvariantCulture));
			}
			return output.ToString();
		}

		/// <summary>
		/// Decodes an HTML-encoded string and sends the resulting output to a TextWriter output stream.
		/// </summary>
		/// <param name="s">The HTML string to decode</param>
		/// <param name="output">The TextWriter output stream containing the decoded string. </param>
		public static void HtmlDecode(string s, TextWriter output) {
			if (s != null)
				output.Write(HtmlDecode(s));
		}

		/// <summary>
		/// HTML-encodes a string and returns the encoded string.
		/// </summary>
		/// <param name="s">The text string to encode. </param>
		/// <returns>The HTML-encoded text.</returns>
		public static string HtmlEncode(string s) {
			if (s == null)
				return null;

			bool needEncode = false;
			for (int i = 0; i < s.Length; i++) {
				char c = s[i];
				if (c == '&' || c == '"' || c == '<' || c == '>' || c > 159) {
					needEncode = true;
					break;
				}
			}

			if (!needEncode)
				return s;

			StringBuilder output = new StringBuilder();

			int len = s.Length;
			for (int i = 0; i < len; i++)
				switch (s[i]) {
					case '&':
						output.Append("&amp;");
						break;
					case '>':
						output.Append("&gt;");
						break;
					case '<':
						output.Append("&lt;");
						break;
					case '"':
						output.Append("&quot;");
						break;
					default:
						// MS starts encoding with &# from 160 and stops at 255.
						// We don't do that. One reason is the 65308/65310 unicode
						// characters that look like '<' and '>'.
#if TARGET_JVM
                        if (s [i] > 159 && s [i] < 256) {
#else
						if (s[i] > 159) {
#endif
							output.Append("&#");
							output.Append(((int)s[i]).ToString(Helpers.InvariantCulture));
							output.Append(";");
						} else {
							output.Append(s[i]);
						}
						break;
				}
			return output.ToString();
		}

		/// <summary>
		/// HTML-encodes a string and sends the resulting output to a TextWriter output stream.
		/// </summary>
		/// <param name="s">The string to encode. </param>
		/// <param name="output">The TextWriter output stream containing the encoded string. </param>
		public static void HtmlEncode(string s, TextWriter output) {
			if (s != null)
				output.Write(HtmlEncode(s));
		}

#if NET_1_1
		public static string UrlPathEncode(string s)
		{
			if (s == null || s.Length == 0)
				return s;

			MemoryStream result = new MemoryStream ();
			int length = s.Length;
            for (int i = 0; i < length; i++) {
				UrlPathEncodeChar(s [i], result);
			}
			return Encoding.ASCII.GetString(result.ToArray ());
		}
		
		static void UrlPathEncodeChar(char c, Stream result) {
#if NET_2_0
			if (c < 33 || c > 126) {
#else
			if (c > 127) {
#endif
				byte [] bIn = Encoding.UTF8.GetBytes(c.ToString());
				for (int i = 0; i < bIn.Length; i++) {
					result.WriteByte((byte) '%');
					int idx = ((int) bIn [i]) >> 4;
					result.WriteByte((byte) hexChars [idx]);
					idx = ((int) bIn [i]) & 0x0F;
					result.WriteByte((byte) hexChars [idx]);
				}
			}
			else if (c == ' ') {
				result.WriteByte((byte) '%');
				result.WriteByte((byte) '2');
				result.WriteByte((byte) '0');
			}
			else
				result.WriteByte((byte) c);
		}
#endif

#if NET_2_0
		class HttpQSCollection : NameValueCollection {
			public override string ToString ()
			{
				int count = Count;
				if (count == 0)
					return "";

				StringBuilder sb = new StringBuilder ();
				string [] keys = AllKeys;
				for (int i = 0; i < count; i++) {
					sb.AppendFormat ("{0}={1}&", keys [i], this [keys [i]]);
				}
				if (sb.Length > 0)
					sb.Length--;
				return sb.ToString ();
			}
		}

		public static NameValueCollection ParseQueryString(string query)
		{
			return ParseQueryString(query, Encoding.UTF8);
		}

		public static NameValueCollection ParseQueryString(string query, Encoding encoding)
		{
			if (query == null)
				throw new ArgumentNullException("query");
			if (encoding == null)
				throw new ArgumentNullException("encoding");
			if (query.Length == 0 || (query.Length == 1 && query[0] == '?'))
				return new NameValueCollection();
			if (query[0] == '?')
				query = query.Substring(1);
				
			NameValueCollection result = new HttpQSCollection();
			ParseQueryString(query, encoding, result);
			return result;
		} 				
#endif

		internal static void ParseQueryString(string query, Encoding encoding, NameValueCollection result) {
			if (query.Length == 0)
				return;

			string decoded = HtmlDecode(query);
			int decodedLength = decoded.Length;
			int namePos = 0;
			bool first = true;
			while (namePos <= decodedLength) {
				int valuePos = -1, valueEnd = -1;
				for (int q = namePos; q < decodedLength; q++) {
					if (valuePos == -1 && decoded[q] == '=') {
						valuePos = q + 1;
					} else if (decoded[q] == '&') {
						valueEnd = q;
						break;
					}
				}

				if (first) {
					first = false;
					if (decoded[namePos] == '?')
						namePos++;
				}

				string name, value;
				if (valuePos == -1) {
					name = null;
					valuePos = namePos;
				} else {
					name = UrlDecode(decoded.Substring(namePos, valuePos - namePos - 1), encoding);
				}
				if (valueEnd < 0) {
					namePos = -1;
					valueEnd = decoded.Length;
				} else {
					namePos = valueEnd + 1;
				}
				value = UrlDecode(decoded.Substring(valuePos, valueEnd - valuePos), encoding);

				result.Add(name, value);
				if (namePos == -1)
					break;
			}
		}
		#endregion // Methods
	}
}
