/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.wicket.util.string;

import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;

import org.apache.wicket.util.collections.IntHashMap;
import org.apache.wicket.util.lang.Generics;

/**
 * <p>
 * Provides HTML and XML entity utilities.
 * </p>
 * 
 * @see <a href="http://hotwired.lycos.com/webmonkey/reference/special_characters/">ISO Entities</a>
 * @see <a href="http://www.w3.org/TR/REC-html32#latin1">HTML 3.2 Character Entities for ISO
 *      Latin-1</a>
 * @see <a href="http://www.w3.org/TR/REC-html40/sgml/entities.html">HTML 4.0 Character entity
 *      references</a>
 * @see <a href="http://www.w3.org/TR/html401/charset.html#h-5.3">HTML 4.01 Character References</a>
 * @see <a href="http://www.w3.org/TR/html401/charset.html#code-position">HTML 4.01 Code
 *      positions</a>
 * 
 * @author <a href="mailto:alex@purpletech.com">Alexander Day Chaffee</a>
 * @author <a href="mailto:ggregory@seagullsw.com">Gary Gregory</a>
 * @since 2.0
 * @version $Id$
 */
// Copy from commons-lang ver. 2.6. Non-modified.
class Entities
{

	private static final String[][] BASIC_ARRAY = { { "quot", "34" }, // " - double-quote
			{ "amp", "38" }, // & - ampersand
			{ "lt", "60" }, // < - less-than
			{ "gt", "62" }, // > - greater-than
	};

	private static final String[][] APOS_ARRAY = { { "apos", "39" }, // XML apostrophe
	};

	// package scoped for testing
	static final String[][] ISO8859_1_ARRAY = { { "nbsp", "160" }, // non-breaking space
			{ "iexcl", "161" }, // inverted exclamation mark
			{ "cent", "162" }, // cent sign
			{ "pound", "163" }, // pound sign
			{ "curren", "164" }, // currency sign
			{ "yen", "165" }, // yen sign = yuan sign
			{ "brvbar", "166" }, // broken bar = broken vertical bar
			{ "sect", "167" }, // section sign
			{ "uml", "168" }, // diaeresis = spacing diaeresis
			{ "copy", "169" }, // � - copyright sign
			{ "ordf", "170" }, // feminine ordinal indicator
			{ "laquo", "171" }, // left-pointing double angle quotation mark = left pointing
// guillemet
			{ "not", "172" }, // not sign
			{ "shy", "173" }, // soft hyphen = discretionary hyphen
			{ "reg", "174" }, // � - registered trademark sign
			{ "macr", "175" }, // macron = spacing macron = overline = APL overbar
			{ "deg", "176" }, // degree sign
			{ "plusmn", "177" }, // plus-minus sign = plus-or-minus sign
			{ "sup2", "178" }, // superscript two = superscript digit two = squared
			{ "sup3", "179" }, // superscript three = superscript digit three = cubed
			{ "acute", "180" }, // acute accent = spacing acute
			{ "micro", "181" }, // micro sign
			{ "para", "182" }, // pilcrow sign = paragraph sign
			{ "middot", "183" }, // middle dot = Georgian comma = Greek middle dot
			{ "cedil", "184" }, // cedilla = spacing cedilla
			{ "sup1", "185" }, // superscript one = superscript digit one
			{ "ordm", "186" }, // masculine ordinal indicator
			{ "raquo", "187" }, // right-pointing double angle quotation mark = right pointing
// guillemet
			{ "frac14", "188" }, // vulgar fraction one quarter = fraction one quarter
			{ "frac12", "189" }, // vulgar fraction one half = fraction one half
			{ "frac34", "190" }, // vulgar fraction three quarters = fraction three quarters
			{ "iquest", "191" }, // inverted question mark = turned question mark
			{ "Agrave", "192" }, // � - uppercase A, grave accent
			{ "Aacute", "193" }, // � - uppercase A, acute accent
			{ "Acirc", "194" }, // � - uppercase A, circumflex accent
			{ "Atilde", "195" }, // � - uppercase A, tilde
			{ "Auml", "196" }, // � - uppercase A, umlaut
			{ "Aring", "197" }, // � - uppercase A, ring
			{ "AElig", "198" }, // � - uppercase AE
			{ "Ccedil", "199" }, // � - uppercase C, cedilla
			{ "Egrave", "200" }, // � - uppercase E, grave accent
			{ "Eacute", "201" }, // � - uppercase E, acute accent
			{ "Ecirc", "202" }, // � - uppercase E, circumflex accent
			{ "Euml", "203" }, // � - uppercase E, umlaut
			{ "Igrave", "204" }, // � - uppercase I, grave accent
			{ "Iacute", "205" }, // � - uppercase I, acute accent
			{ "Icirc", "206" }, // � - uppercase I, circumflex accent
			{ "Iuml", "207" }, // � - uppercase I, umlaut
			{ "ETH", "208" }, // � - uppercase Eth, Icelandic
			{ "Ntilde", "209" }, // � - uppercase N, tilde
			{ "Ograve", "210" }, // � - uppercase O, grave accent
			{ "Oacute", "211" }, // � - uppercase O, acute accent
			{ "Ocirc", "212" }, // � - uppercase O, circumflex accent
			{ "Otilde", "213" }, // � - uppercase O, tilde
			{ "Ouml", "214" }, // � - uppercase O, umlaut
			{ "times", "215" }, // multiplication sign
			{ "Oslash", "216" }, // � - uppercase O, slash
			{ "Ugrave", "217" }, // � - uppercase U, grave accent
			{ "Uacute", "218" }, // � - uppercase U, acute accent
			{ "Ucirc", "219" }, // � - uppercase U, circumflex accent
			{ "Uuml", "220" }, // � - uppercase U, umlaut
			{ "Yacute", "221" }, // � - uppercase Y, acute accent
			{ "THORN", "222" }, // � - uppercase THORN, Icelandic
			{ "szlig", "223" }, // � - lowercase sharps, German
			{ "agrave", "224" }, // � - lowercase a, grave accent
			{ "aacute", "225" }, // � - lowercase a, acute accent
			{ "acirc", "226" }, // � - lowercase a, circumflex accent
			{ "atilde", "227" }, // � - lowercase a, tilde
			{ "auml", "228" }, // � - lowercase a, umlaut
			{ "aring", "229" }, // � - lowercase a, ring
			{ "aelig", "230" }, // � - lowercase ae
			{ "ccedil", "231" }, // � - lowercase c, cedilla
			{ "egrave", "232" }, // � - lowercase e, grave accent
			{ "eacute", "233" }, // � - lowercase e, acute accent
			{ "ecirc", "234" }, // � - lowercase e, circumflex accent
			{ "euml", "235" }, // � - lowercase e, umlaut
			{ "igrave", "236" }, // � - lowercase i, grave accent
			{ "iacute", "237" }, // � - lowercase i, acute accent
			{ "icirc", "238" }, // � - lowercase i, circumflex accent
			{ "iuml", "239" }, // � - lowercase i, umlaut
			{ "eth", "240" }, // � - lowercase eth, Icelandic
			{ "ntilde", "241" }, // � - lowercase n, tilde
			{ "ograve", "242" }, // � - lowercase o, grave accent
			{ "oacute", "243" }, // � - lowercase o, acute accent
			{ "ocirc", "244" }, // � - lowercase o, circumflex accent
			{ "otilde", "245" }, // � - lowercase o, tilde
			{ "ouml", "246" }, // � - lowercase o, umlaut
			{ "divide", "247" }, // division sign
			{ "oslash", "248" }, // � - lowercase o, slash
			{ "ugrave", "249" }, // � - lowercase u, grave accent
			{ "uacute", "250" }, // � - lowercase u, acute accent
			{ "ucirc", "251" }, // � - lowercase u, circumflex accent
			{ "uuml", "252" }, // � - lowercase u, umlaut
			{ "yacute", "253" }, // � - lowercase y, acute accent
			{ "thorn", "254" }, // � - lowercase thorn, Icelandic
			{ "yuml", "255" }, // � - lowercase y, umlaut
	};

	// http://www.w3.org/TR/REC-html40/sgml/entities.html
	// package scoped for testing
	static final String[][] HTML40_ARRAY = {
			// <!-- Latin Extended-B -->
			{ "fnof", "402" }, // latin small f with hook = function= florin, U+0192 ISOtech -->
			// <!-- Greek -->
			{ "Alpha", "913" }, // greek capital letter alpha, U+0391 -->
			{ "Beta", "914" }, // greek capital letter beta, U+0392 -->
			{ "Gamma", "915" }, // greek capital letter gamma,U+0393 ISOgrk3 -->
			{ "Delta", "916" }, // greek capital letter delta,U+0394 ISOgrk3 -->
			{ "Epsilon", "917" }, // greek capital letter epsilon, U+0395 -->
			{ "Zeta", "918" }, // greek capital letter zeta, U+0396 -->
			{ "Eta", "919" }, // greek capital letter eta, U+0397 -->
			{ "Theta", "920" }, // greek capital letter theta,U+0398 ISOgrk3 -->
			{ "Iota", "921" }, // greek capital letter iota, U+0399 -->
			{ "Kappa", "922" }, // greek capital letter kappa, U+039A -->
			{ "Lambda", "923" }, // greek capital letter lambda,U+039B ISOgrk3 -->
			{ "Mu", "924" }, // greek capital letter mu, U+039C -->
			{ "Nu", "925" }, // greek capital letter nu, U+039D -->
			{ "Xi", "926" }, // greek capital letter xi, U+039E ISOgrk3 -->
			{ "Omicron", "927" }, // greek capital letter omicron, U+039F -->
			{ "Pi", "928" }, // greek capital letter pi, U+03A0 ISOgrk3 -->
			{ "Rho", "929" }, // greek capital letter rho, U+03A1 -->
			// <!-- there is no Sigmaf, and no U+03A2 character either -->
			{ "Sigma", "931" }, // greek capital letter sigma,U+03A3 ISOgrk3 -->
			{ "Tau", "932" }, // greek capital letter tau, U+03A4 -->
			{ "Upsilon", "933" }, // greek capital letter upsilon,U+03A5 ISOgrk3 -->
			{ "Phi", "934" }, // greek capital letter phi,U+03A6 ISOgrk3 -->
			{ "Chi", "935" }, // greek capital letter chi, U+03A7 -->
			{ "Psi", "936" }, // greek capital letter psi,U+03A8 ISOgrk3 -->
			{ "Omega", "937" }, // greek capital letter omega,U+03A9 ISOgrk3 -->
			{ "alpha", "945" }, // greek small letter alpha,U+03B1 ISOgrk3 -->
			{ "beta", "946" }, // greek small letter beta, U+03B2 ISOgrk3 -->
			{ "gamma", "947" }, // greek small letter gamma,U+03B3 ISOgrk3 -->
			{ "delta", "948" }, // greek small letter delta,U+03B4 ISOgrk3 -->
			{ "epsilon", "949" }, // greek small letter epsilon,U+03B5 ISOgrk3 -->
			{ "zeta", "950" }, // greek small letter zeta, U+03B6 ISOgrk3 -->
			{ "eta", "951" }, // greek small letter eta, U+03B7 ISOgrk3 -->
			{ "theta", "952" }, // greek small letter theta,U+03B8 ISOgrk3 -->
			{ "iota", "953" }, // greek small letter iota, U+03B9 ISOgrk3 -->
			{ "kappa", "954" }, // greek small letter kappa,U+03BA ISOgrk3 -->
			{ "lambda", "955" }, // greek small letter lambda,U+03BB ISOgrk3 -->
			{ "mu", "956" }, // greek small letter mu, U+03BC ISOgrk3 -->
			{ "nu", "957" }, // greek small letter nu, U+03BD ISOgrk3 -->
			{ "xi", "958" }, // greek small letter xi, U+03BE ISOgrk3 -->
			{ "omicron", "959" }, // greek small letter omicron, U+03BF NEW -->
			{ "pi", "960" }, // greek small letter pi, U+03C0 ISOgrk3 -->
			{ "rho", "961" }, // greek small letter rho, U+03C1 ISOgrk3 -->
			{ "sigmaf", "962" }, // greek small letter final sigma,U+03C2 ISOgrk3 -->
			{ "sigma", "963" }, // greek small letter sigma,U+03C3 ISOgrk3 -->
			{ "tau", "964" }, // greek small letter tau, U+03C4 ISOgrk3 -->
			{ "upsilon", "965" }, // greek small letter upsilon,U+03C5 ISOgrk3 -->
			{ "phi", "966" }, // greek small letter phi, U+03C6 ISOgrk3 -->
			{ "chi", "967" }, // greek small letter chi, U+03C7 ISOgrk3 -->
			{ "psi", "968" }, // greek small letter psi, U+03C8 ISOgrk3 -->
			{ "omega", "969" }, // greek small letter omega,U+03C9 ISOgrk3 -->
			{ "thetasym", "977" }, // greek small letter theta symbol,U+03D1 NEW -->
			{ "upsih", "978" }, // greek upsilon with hook symbol,U+03D2 NEW -->
			{ "piv", "982" }, // greek pi symbol, U+03D6 ISOgrk3 -->
			// <!-- General Punctuation -->
			{ "bull", "8226" }, // bullet = black small circle,U+2022 ISOpub -->
			// <!-- bullet is NOT the same as bullet operator, U+2219 -->
			{ "hellip", "8230" }, // horizontal ellipsis = three dot leader,U+2026 ISOpub -->
			{ "prime", "8242" }, // prime = minutes = feet, U+2032 ISOtech -->
			{ "Prime", "8243" }, // double prime = seconds = inches,U+2033 ISOtech -->
			{ "oline", "8254" }, // overline = spacing overscore,U+203E NEW -->
			{ "frasl", "8260" }, // fraction slash, U+2044 NEW -->
			// <!-- Letterlike Symbols -->
			{ "weierp", "8472" }, // script capital P = power set= Weierstrass p, U+2118 ISOamso -->
			{ "image", "8465" }, // blackletter capital I = imaginary part,U+2111 ISOamso -->
			{ "real", "8476" }, // blackletter capital R = real part symbol,U+211C ISOamso -->
			{ "trade", "8482" }, // trade mark sign, U+2122 ISOnum -->
			{ "alefsym", "8501" }, // alef symbol = first transfinite cardinal,U+2135 NEW -->
			// <!-- alef symbol is NOT the same as hebrew letter alef,U+05D0 although the
			// same glyph could be used to depict both characters -->
			// <!-- Arrows -->
			{ "larr", "8592" }, // leftwards arrow, U+2190 ISOnum -->
			{ "uarr", "8593" }, // upwards arrow, U+2191 ISOnum-->
			{ "rarr", "8594" }, // rightwards arrow, U+2192 ISOnum -->
			{ "darr", "8595" }, // downwards arrow, U+2193 ISOnum -->
			{ "harr", "8596" }, // left right arrow, U+2194 ISOamsa -->
			{ "crarr", "8629" }, // downwards arrow with corner leftwards= carriage return, U+21B5
// NEW -->
			{ "lArr", "8656" }, // leftwards double arrow, U+21D0 ISOtech -->
			// <!-- ISO 10646 does not say that lArr is the same as the 'is implied by'
			// arrow but also does not have any other character for that function.
			// So ? lArr canbe used for 'is implied by' as ISOtech suggests -->
			{ "uArr", "8657" }, // upwards double arrow, U+21D1 ISOamsa -->
			{ "rArr", "8658" }, // rightwards double arrow,U+21D2 ISOtech -->
			// <!-- ISO 10646 does not say this is the 'implies' character but does not
			// have another character with this function so ?rArr can be used for
			// 'implies' as ISOtech suggests -->
			{ "dArr", "8659" }, // downwards double arrow, U+21D3 ISOamsa -->
			{ "hArr", "8660" }, // left right double arrow,U+21D4 ISOamsa -->
			// <!-- Mathematical Operators -->
			{ "forall", "8704" }, // for all, U+2200 ISOtech -->
			{ "part", "8706" }, // partial differential, U+2202 ISOtech -->
			{ "exist", "8707" }, // there exists, U+2203 ISOtech -->
			{ "empty", "8709" }, // empty set = null set = diameter,U+2205 ISOamso -->
			{ "nabla", "8711" }, // nabla = backward difference,U+2207 ISOtech -->
			{ "isin", "8712" }, // element of, U+2208 ISOtech -->
			{ "notin", "8713" }, // not an element of, U+2209 ISOtech -->
			{ "ni", "8715" }, // contains as member, U+220B ISOtech -->
			// <!-- should there be a more memorable name than 'ni'? -->
			{ "prod", "8719" }, // n-ary product = product sign,U+220F ISOamsb -->
			// <!-- prod is NOT the same character as U+03A0 'greek capital letter pi'
			// though the same glyph might be used for both -->
			{ "sum", "8721" }, // n-ary summation, U+2211 ISOamsb -->
			// <!-- sum is NOT the same character as U+03A3 'greek capital letter sigma'
			// though the same glyph might be used for both -->
			{ "minus", "8722" }, // minus sign, U+2212 ISOtech -->
			{ "lowast", "8727" }, // asterisk operator, U+2217 ISOtech -->
			{ "radic", "8730" }, // square root = radical sign,U+221A ISOtech -->
			{ "prop", "8733" }, // proportional to, U+221D ISOtech -->
			{ "infin", "8734" }, // infinity, U+221E ISOtech -->
			{ "ang", "8736" }, // angle, U+2220 ISOamso -->
			{ "and", "8743" }, // logical and = wedge, U+2227 ISOtech -->
			{ "or", "8744" }, // logical or = vee, U+2228 ISOtech -->
			{ "cap", "8745" }, // intersection = cap, U+2229 ISOtech -->
			{ "cup", "8746" }, // union = cup, U+222A ISOtech -->
			{ "int", "8747" }, // integral, U+222B ISOtech -->
			{ "there4", "8756" }, // therefore, U+2234 ISOtech -->
			{ "sim", "8764" }, // tilde operator = varies with = similar to,U+223C ISOtech -->
			// <!-- tilde operator is NOT the same character as the tilde, U+007E,although
			// the same glyph might be used to represent both -->
			{ "cong", "8773" }, // approximately equal to, U+2245 ISOtech -->
			{ "asymp", "8776" }, // almost equal to = asymptotic to,U+2248 ISOamsr -->
			{ "ne", "8800" }, // not equal to, U+2260 ISOtech -->
			{ "equiv", "8801" }, // identical to, U+2261 ISOtech -->
			{ "le", "8804" }, // less-than or equal to, U+2264 ISOtech -->
			{ "ge", "8805" }, // greater-than or equal to,U+2265 ISOtech -->
			{ "sub", "8834" }, // subset of, U+2282 ISOtech -->
			{ "sup", "8835" }, // superset of, U+2283 ISOtech -->
			// <!-- note that nsup, 'not a superset of, U+2283' is not covered by the
			// Symbol font encoding and is not included. Should it be, for symmetry?
			// It is in ISOamsn --> <!ENTITY nsub", "8836"},
			// not a subset of, U+2284 ISOamsn -->
			{ "sube", "8838" }, // subset of or equal to, U+2286 ISOtech -->
			{ "supe", "8839" }, // superset of or equal to,U+2287 ISOtech -->
			{ "oplus", "8853" }, // circled plus = direct sum,U+2295 ISOamsb -->
			{ "otimes", "8855" }, // circled times = vector product,U+2297 ISOamsb -->
			{ "perp", "8869" }, // up tack = orthogonal to = perpendicular,U+22A5 ISOtech -->
			{ "sdot", "8901" }, // dot operator, U+22C5 ISOamsb -->
			// <!-- dot operator is NOT the same character as U+00B7 middle dot -->
			// <!-- Miscellaneous Technical -->
			{ "lceil", "8968" }, // left ceiling = apl upstile,U+2308 ISOamsc -->
			{ "rceil", "8969" }, // right ceiling, U+2309 ISOamsc -->
			{ "lfloor", "8970" }, // left floor = apl downstile,U+230A ISOamsc -->
			{ "rfloor", "8971" }, // right floor, U+230B ISOamsc -->
			{ "lang", "9001" }, // left-pointing angle bracket = bra,U+2329 ISOtech -->
			// <!-- lang is NOT the same character as U+003C 'less than' or U+2039 'single
// left-pointing angle quotation
			// mark' -->
			{ "rang", "9002" }, // right-pointing angle bracket = ket,U+232A ISOtech -->
			// <!-- rang is NOT the same character as U+003E 'greater than' or U+203A
			// 'single right-pointing angle quotation mark' -->
			// <!-- Geometric Shapes -->
			{ "loz", "9674" }, // lozenge, U+25CA ISOpub -->
			// <!-- Miscellaneous Symbols -->
			{ "spades", "9824" }, // black spade suit, U+2660 ISOpub -->
			// <!-- black here seems to mean filled as opposed to hollow -->
			{ "clubs", "9827" }, // black club suit = shamrock,U+2663 ISOpub -->
			{ "hearts", "9829" }, // black heart suit = valentine,U+2665 ISOpub -->
			{ "diams", "9830" }, // black diamond suit, U+2666 ISOpub -->

			// <!-- Latin Extended-A -->
			{ "OElig", "338" }, // -- latin capital ligature OE,U+0152 ISOlat2 -->
			{ "oelig", "339" }, // -- latin small ligature oe, U+0153 ISOlat2 -->
			// <!-- ligature is a misnomer, this is a separate character in some languages -->
			{ "Scaron", "352" }, // -- latin capital letter S with caron,U+0160 ISOlat2 -->
			{ "scaron", "353" }, // -- latin small letter s with caron,U+0161 ISOlat2 -->
			{ "Yuml", "376" }, // -- latin capital letter Y with diaeresis,U+0178 ISOlat2 -->
			// <!-- Spacing Modifier Letters -->
			{ "circ", "710" }, // -- modifier letter circumflex accent,U+02C6 ISOpub -->
			{ "tilde", "732" }, // small tilde, U+02DC ISOdia -->
			// <!-- General Punctuation -->
			{ "ensp", "8194" }, // en space, U+2002 ISOpub -->
			{ "emsp", "8195" }, // em space, U+2003 ISOpub -->
			{ "thinsp", "8201" }, // thin space, U+2009 ISOpub -->
			{ "zwnj", "8204" }, // zero width non-joiner,U+200C NEW RFC 2070 -->
			{ "zwj", "8205" }, // zero width joiner, U+200D NEW RFC 2070 -->
			{ "lrm", "8206" }, // left-to-right mark, U+200E NEW RFC 2070 -->
			{ "rlm", "8207" }, // right-to-left mark, U+200F NEW RFC 2070 -->
			{ "ndash", "8211" }, // en dash, U+2013 ISOpub -->
			{ "mdash", "8212" }, // em dash, U+2014 ISOpub -->
			{ "lsquo", "8216" }, // left single quotation mark,U+2018 ISOnum -->
			{ "rsquo", "8217" }, // right single quotation mark,U+2019 ISOnum -->
			{ "sbquo", "8218" }, // single low-9 quotation mark, U+201A NEW -->
			{ "ldquo", "8220" }, // left double quotation mark,U+201C ISOnum -->
			{ "rdquo", "8221" }, // right double quotation mark,U+201D ISOnum -->
			{ "bdquo", "8222" }, // double low-9 quotation mark, U+201E NEW -->
			{ "dagger", "8224" }, // dagger, U+2020 ISOpub -->
			{ "Dagger", "8225" }, // double dagger, U+2021 ISOpub -->
			{ "permil", "8240" }, // per mille sign, U+2030 ISOtech -->
			{ "lsaquo", "8249" }, // single left-pointing angle quotation mark,U+2039 ISO proposed
// -->
			// <!-- lsaquo is proposed but not yet ISO standardized -->
			{ "rsaquo", "8250" }, // single right-pointing angle quotation mark,U+203A ISO proposed
// -->
			// <!-- rsaquo is proposed but not yet ISO standardized -->
			{ "euro", "8364" }, // -- euro sign, U+20AC NEW -->
	};

	/**
	 * <p>
	 * The set of entities supported by standard XML.
	 * </p>
	 */
	public static final Entities XML;

	/**
	 * <p>
	 * The set of entities supported by HTML 3.2.
	 * </p>
	 */
	public static final Entities HTML32;

	/**
	 * <p>
	 * The set of entities supported by HTML 4.0.
	 * </p>
	 */
	public static final Entities HTML40;

	static
	{
		Entities xml = new Entities();
		xml.addEntities(BASIC_ARRAY);
		xml.addEntities(APOS_ARRAY);
		XML = xml;
	}

	static
	{
		Entities html32 = new Entities();
		html32.addEntities(BASIC_ARRAY);
		html32.addEntities(ISO8859_1_ARRAY);
		HTML32 = html32;
	}

	static
	{
		Entities html40 = new Entities();
		fillWithHtml40Entities(html40);
		HTML40 = html40;
	}

	/**
	 * <p>
	 * Fills the specified entities instance with HTML 40 entities.
	 * </p>
	 * 
	 * @param entities
	 *            the instance to be filled.
	 */
	static void fillWithHtml40Entities(Entities entities)
	{
		entities.addEntities(BASIC_ARRAY);
		entities.addEntities(ISO8859_1_ARRAY);
		entities.addEntities(HTML40_ARRAY);
	}

	static interface EntityMap
	{
		/**
		 * <p>
		 * Add an entry to this entity map.
		 * </p>
		 * 
		 * @param name
		 *            the entity name
		 * @param value
		 *            the entity value
		 */
		void add(String name, int value);

		/**
		 * <p>
		 * Returns the name of the entity identified by the specified value.
		 * </p>
		 * 
		 * @param value
		 *            the value to locate
		 * @return entity name associated with the specified value
		 */
		String name(int value);

		/**
		 * <p>
		 * Returns the value of the entity identified by the specified name.
		 * </p>
		 * 
		 * @param name
		 *            the name to locate
		 * @return entity value associated with the specified name
		 */
		int value(String name);
	}

	static class PrimitiveEntityMap implements EntityMap
	{
		private final Map<String, Integer> mapNameToValue = Generics.newHashMap();

		private final IntHashMap<String> mapValueToName = new IntHashMap<>();

		// TODO not thread-safe as there is a window between changing the two maps
		@Override
		public void add(String name, int value)
		{
			mapNameToValue.put(name, Integer.valueOf(value));
			mapValueToName.put(value, name);
		}

		@Override
		public String name(int value)
		{
			return mapValueToName.get(value);
		}

		@Override
		public int value(String name)
		{
			Integer value = mapNameToValue.get(name);
			if (value == null)
			{
				return -1;
			}
			return value.intValue();
		}
	}

	static abstract class MapIntMap implements Entities.EntityMap
	{
		protected final Map<String, Integer> mapNameToValue;

		protected final Map<Integer, String> mapValueToName;

		/**
		 * Construct a new instance with specified maps.
		 * 
		 * @param nameToValue
		 *            name to value map
		 * @param valueToName
		 *            value to namee map
		 */
		MapIntMap(Map<String, Integer> nameToValue, Map<Integer, String> valueToName)
		{
			mapNameToValue = nameToValue;
			mapValueToName = valueToName;
		}

		@Override
		public void add(String name, int value)
		{
			mapNameToValue.put(name, new Integer(value));
			mapValueToName.put(Integer.valueOf(value), name);
		}

		@Override
		public String name(int value)
		{
			return mapValueToName.get(Integer.valueOf(value));
		}

		/**
		 * {@inheritDoc}
		 */
		@Override
		public int value(String name)
		{
			Integer value = mapNameToValue.get(name);
			if (value == null)
			{
				return -1;
			}
			return value.intValue();
		}
	}

	static class HashEntityMap extends MapIntMap
	{
		/**
		 * Constructs a new instance of <code>HashEntityMap</code>.
		 */
		public HashEntityMap()
		{
			super(new HashMap<String, Integer>(), new HashMap<Integer, String>());
		}
	}

	static class TreeEntityMap extends MapIntMap
	{
		/**
		 * Constructs a new instance of <code>TreeEntityMap</code>.
		 */
		public TreeEntityMap()
		{
			super(new TreeMap<String, Integer>(), new TreeMap<Integer, String>());
		}
	}

	static class LookupEntityMap extends PrimitiveEntityMap
	{
		// TODO this class is not thread-safe
		private String[] lookupTable;

		private static final int LOOKUP_TABLE_SIZE = 256;

		@Override
		public String name(int value)
		{
			if (value < LOOKUP_TABLE_SIZE)
			{
				return lookupTable()[value];
			}
			return super.name(value);
		}

		/**
		 * Returns the lookup table for this entity map. The lookup table is created if it has not
		 * been previously.
		 * 
		 * @return the lookup table
		 */
		private String[] lookupTable()
		{
			if (lookupTable == null)
			{
				createLookupTable();
			}
			return lookupTable;
		}

		/**
		 * Creates an entity lookup table of LOOKUP_TABLE_SIZE elements, initialized with entity
		 * names.
		 */
		private void createLookupTable()
		{
			lookupTable = new String[LOOKUP_TABLE_SIZE];
			for (int i = 0; i < LOOKUP_TABLE_SIZE; ++i)
			{
				lookupTable[i] = super.name(i);
			}
		}
	}

	static class ArrayEntityMap implements EntityMap
	{
		// TODO this class is not thread-safe
		protected final int growBy;

		protected int size = 0;

		protected String[] names;

		protected int[] values;

		/**
		 * Constructs a new instance of <code>ArrayEntityMap</code>.
		 */
		public ArrayEntityMap()
		{
			growBy = 100;
			names = new String[growBy];
			values = new int[growBy];
		}

		/**
		 * Constructs a new instance of <code>ArrayEntityMap</code> specifying the size by which the
		 * array should grow.
		 * 
		 * @param growBy
		 *            array will be initialized to and will grow by this amount
		 */
		public ArrayEntityMap(int growBy)
		{
			this.growBy = growBy;
			names = new String[growBy];
			values = new int[growBy];
		}

		/**
		 * {@inheritDoc}
		 */
		@Override
		public void add(String name, int value)
		{
			ensureCapacity(size + 1);
			names[size] = name;
			values[size] = value;
			size++;
		}

		/**
		 * Verifies the capacity of the entity array, adjusting the size if necessary.
		 * 
		 * @param capacity
		 *            size the array should be
		 */
		protected void ensureCapacity(int capacity)
		{
			if (capacity > names.length)
			{
				int newSize = Math.max(capacity, size + growBy);
				String[] newNames = new String[newSize];
				System.arraycopy(names, 0, newNames, 0, size);
				names = newNames;
				int[] newValues = new int[newSize];
				System.arraycopy(values, 0, newValues, 0, size);
				values = newValues;
			}
		}

		/**
		 * {@inheritDoc}
		 */
		@Override
		public String name(int value)
		{
			for (int i = 0; i < size; ++i)
			{
				if (values[i] == value)
				{
					return names[i];
				}
			}
			return null;
		}

		/**
		 * {@inheritDoc}
		 */
		@Override
		public int value(String name)
		{
			for (int i = 0; i < size; ++i)
			{
				if (names[i].equals(name))
				{
					return values[i];
				}
			}
			return -1;
		}
	}

	static class BinaryEntityMap extends ArrayEntityMap
	{

		// TODO - not thread-safe, because parent is not. Also references size.

		/**
		 * Constructs a new instance of <code>BinaryEntityMap</code>.
		 */
		public BinaryEntityMap()
		{
			super();
		}

		/**
		 * Constructs a new instance of <code>ArrayEntityMap</code> specifying the size by which the
		 * underlying array should grow.
		 * 
		 * @param growBy
		 *            array will be initialized to and will grow by this amount
		 */
		public BinaryEntityMap(int growBy)
		{
			super(growBy);
		}

		/**
		 * Performs a binary search of the entity array for the specified key. This method is based
		 * on code in {@link java.util.Arrays}.
		 * 
		 * @param key
		 *            the key to be found
		 * @return the index of the entity array matching the specified key
		 */
		private int binarySearch(int key)
		{
			int low = 0;
			int high = size - 1;

			while (low <= high)
			{
				int mid = (low + high) >>> 1;
				int midVal = values[mid];

				if (midVal < key)
				{
					low = mid + 1;
				}
				else if (midVal > key)
				{
					high = mid - 1;
				}
				else
				{
					return mid; // key found
				}
			}
			return -(low + 1); // key not found.
		}

		/**
		 * {@inheritDoc}
		 */
		@Override
		public void add(String name, int value)
		{
			ensureCapacity(size + 1);
			int insertAt = binarySearch(value);
			if (insertAt > 0)
			{
				return; // note: this means you can't insert the same value twice
			}
			insertAt = -(insertAt + 1); // binarySearch returns it negative and off-by-one
			System.arraycopy(values, insertAt, values, insertAt + 1, size - insertAt);
			values[insertAt] = value;
			System.arraycopy(names, insertAt, names, insertAt + 1, size - insertAt);
			names[insertAt] = name;
			size++;
		}

		/**
		 * {@inheritDoc}
		 */
		@Override
		public String name(int value)
		{
			int index = binarySearch(value);
			if (index < 0)
			{
				return null;
			}
			return names[index];
		}
	}

	private final EntityMap map;

	/**
	 * Default constructor.
	 */
	public Entities()
	{
		map = new Entities.LookupEntityMap();
	}

	/**
	 * package scoped constructor for testing.
	 * 
	 * @param emap
	 *            entity map.
	 */
	Entities(EntityMap emap)
	{
		map = emap;
	}

	/**
	 * <p>
	 * Adds entities to this entity.
	 * </p>
	 * 
	 * @param entityArray
	 *            array of entities to be added
	 */
	public void addEntities(String[][] entityArray)
	{
		for (int i = 0; i < entityArray.length; ++i)
		{
			addEntity(entityArray[i][0], Integer.parseInt(entityArray[i][1]));
		}
	}

	/**
	 * <p>
	 * Add an entity to this entity.
	 * </p>
	 * 
	 * @param name
	 *            name of the entity
	 * @param value
	 *            vale of the entity
	 */
	public void addEntity(String name, int value)
	{
		map.add(name, value);
	}

	/**
	 * <p>
	 * Returns the name of the entity identified by the specified value.
	 * </p>
	 * 
	 * @param value
	 *            the value to locate
	 * @return entity name associated with the specified value
	 */
	public String entityName(int value)
	{
		return map.name(value);
	}

	/**
	 * <p>
	 * Returns the value of the entity identified by the specified name.
	 * </p>
	 * 
	 * @param name
	 *            the name to locate
	 * @return entity value associated with the specified name
	 */
	public int entityValue(String name)
	{
		return map.value(name);
	}

	/**
	 * <p>
	 * Escapes the characters in a <code>String</code>.
	 * </p>
	 * 
	 * <p>
	 * For example, if you have called addEntity(&quot;foo&quot;, 0xA1), escape(&quot;\u00A1&quot;)
	 * will return &quot;&amp;foo;&quot;
	 * </p>
	 * 
	 * @param str
	 *            The <code>String</code> to escape.
	 * @return A new escaped <code>String</code>.
	 */
	public String escape(String str)
	{
		StringWriter stringWriter = createStringWriter(str);
		try
		{
			this.escape(stringWriter, str);
		}
		catch (IOException e)
		{
			// This should never happen because ALL the StringWriter methods called by
// #escape(Writer, String) do not
			// throw IOExceptions.
			throw new RuntimeException(e);
		}
		return stringWriter.toString();
	}

	/**
	 * <p>
	 * Escapes the characters in the <code>String</code> passed and writes the result to the
	 * <code>Writer</code> passed.
	 * </p>
	 * 
	 * @param writer
	 *            The <code>Writer</code> to write the results of the escaping to. Assumed to be a
	 *            non-null value.
	 * @param str
	 *            The <code>String</code> to escape. Assumed to be a non-null value.
	 * @throws IOException
	 *             when <code>Writer</code> passed throws the exception from calls to the
	 *             {@link Writer#write(int)} methods.
	 * 
	 * @see #escape(String)
	 * @see Writer
	 */
	public void escape(Writer writer, String str) throws IOException
	{
		int len = str.length();
		for (int i = 0; i < len; i++)
		{
			char c = str.charAt(i);
			String entityName = entityName(c);
			if (entityName == null)
			{
				if (c > 0x7F)
				{
					writer.write("&#");
					writer.write(Integer.toString(c, 10));
					writer.write(';');
				}
				else
				{
					writer.write(c);
				}
			}
			else
			{
				writer.write('&');
				writer.write(entityName);
				writer.write(';');
			}
		}
	}

	/**
	 * <p>
	 * Unescapes the entities in a <code>String</code>.
	 * </p>
	 * 
	 * <p>
	 * For example, if you have called addEntity(&quot;foo&quot;, 0xA1),
	 * unescape(&quot;&amp;foo;&quot;) will return &quot;\u00A1&quot;
	 * </p>
	 * 
	 * @param str
	 *            The <code>String</code> to escape.
	 * @return A new escaped <code>String</code>.
	 */
	public String unescape(String str)
	{
		int firstAmp = str.indexOf('&');
		if (firstAmp < 0)
		{
			return str;
		}
		else
		{
			StringWriter stringWriter = createStringWriter(str);
			try
			{
				doUnescape(stringWriter, str, firstAmp);
			}
			catch (IOException e)
			{
				// This should never happen because ALL the StringWriter methods called by
// #escape(Writer, String)
				// do not throw IOExceptions.
				throw new RuntimeException(e);
			}
			return stringWriter.toString();
		}
	}

	/**
	 * Make the StringWriter 10% larger than the source String to avoid growing the writer
	 * 
	 * @param str
	 *            The source string
	 * @return A newly created StringWriter
	 */
	private StringWriter createStringWriter(String str)
	{
		return new StringWriter((int)(str.length() + (str.length() * 0.1)));
	}

	/**
	 * <p>
	 * Unescapes the escaped entities in the <code>String</code> passed and writes the result to the
	 * <code>Writer</code> passed.
	 * </p>
	 * 
	 * @param writer
	 *            The <code>Writer</code> to write the results to; assumed to be non-null.
	 * @param str
	 *            The source <code>String</code> to unescape; assumed to be non-null.
	 * @throws IOException
	 *             when <code>Writer</code> passed throws the exception from calls to the
	 *             {@link Writer#write(int)} methods.
	 * 
	 * @see #escape(String)
	 * @see Writer
	 */
	public void unescape(Writer writer, String str) throws IOException
	{
		int firstAmp = str.indexOf('&');
		if (firstAmp < 0)
		{
			writer.write(str);
			return;
		}
		else
		{
			doUnescape(writer, str, firstAmp);
		}
	}

	/**
	 * Underlying unescape method that allows the optimisation of not starting from the 0 index
	 * again.
	 * 
	 * @param writer
	 *            The <code>Writer</code> to write the results to; assumed to be non-null.
	 * @param str
	 *            The source <code>String</code> to unescape; assumed to be non-null.
	 * @param firstAmp
	 *            The <code>int</code> index of the first ampersand in the source String.
	 * @throws IOException
	 *             when <code>Writer</code> passed throws the exception from calls to the
	 *             {@link Writer#write(int)} methods.
	 */
	private void doUnescape(Writer writer, String str, int firstAmp) throws IOException
	{
		writer.write(str, 0, firstAmp);
		int len = str.length();
		for (int i = firstAmp; i < len; i++)
		{
			char c = str.charAt(i);
			if (c == '&')
			{
				int nextIdx = i + 1;
				int semiColonIdx = str.indexOf(';', nextIdx);
				if (semiColonIdx == -1)
				{
					writer.write(c);
					continue;
				}
				int amphersandIdx = str.indexOf('&', i + 1);
				if (amphersandIdx != -1 && amphersandIdx < semiColonIdx)
				{
					// Then the text looks like &...&...;
					writer.write(c);
					continue;
				}
				String entityContent = str.substring(nextIdx, semiColonIdx);
				int entityValue = -1;
				int entityContentLen = entityContent.length();
				if (entityContentLen > 0)
				{
					if (entityContent.charAt(0) == '#')
					{ // escaped value content is an integer (decimal or
						// hexidecimal)
						if (entityContentLen > 1)
						{
							char isHexChar = entityContent.charAt(1);
							try
							{
								switch (isHexChar)
								{
									case 'X' :
									case 'x' : {
										entityValue = Integer.parseInt(entityContent.substring(2),
											16);
										break;
									}
									default : {
										entityValue = Integer.parseInt(entityContent.substring(1),
											10);
									}
								}
								if (entityValue > 0xFFFF)
								{
									entityValue = -1;
								}
							}
							catch (NumberFormatException e)
							{
								entityValue = -1;
							}
						}
					}
					else
					{ // escaped value content is an entity name
						entityValue = entityValue(entityContent);
					}
				}

				if (entityValue == -1)
				{
					writer.write('&');
					writer.write(entityContent);
					writer.write(';');
				}
				else
				{
					writer.write(entityValue);
				}
				i = semiColonIdx; // move index up to the semi-colon
			}
			else
			{
				writer.write(c);
			}
		}
	}

}
