/*
    * $Source$
    * $Revision$
    *
    * Copyright (C) 2001 Myles Chippendale
    *
    * Part of Melati (http://melati.org), a framework for the rapid
    * development of clean, maintainable web applications.
    *
   * Melati is free software; Permission is granted to copy, distribute
   * and/or modify this software under the terms either:
   *
   * a) the GNU General Public License as published by the Free Software
   *    Foundation; either version 2 of the License, or (at your option)
   *    any later version,
   *
   *    or
   *
   * b) any version of the Melati Software License, as published
   *    at http://melati.org
   *
   * You should have received a copy of the GNU General Public License and
   * the Melati Software License along with this program;
   * if not, write to the Free Software Foundation, Inc.,
   * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the
   * GNU General Public License and visit http://melati.org to obtain the
   * Melati Software License.
   *
   * Feel free to contact the Developers of Melati (http://melati.org),
   * if you would like to work out a different arrangement than the options
   * outlined here.  It is our intention to allow Melati to be used by as
   * wide an audience as possible.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * Contact details for copyright holder:
   *
   *     Myles Chippendale <mylesc At paneris.org>
   */
  package org.melati.util;
  
  import java.io.DataInputStream;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.StringWriter;
  import java.io.Writer;
  import java.nio.charset.Charset;
  import java.nio.charset.CharsetEncoder;
  import java.util.Enumeration;
  
  import javax.swing.text.AttributeSet;
  import javax.swing.text.html.HTML;
  import javax.swing.text.html.parser.AttributeList;
  import javax.swing.text.html.parser.ContentModel;
  import javax.swing.text.html.parser.DTD;
  import javax.swing.text.html.parser.DTDConstants;
  import javax.swing.text.html.parser.Element;
  
  /**
   * An assortment of useful things to do with HTML.
   */
  public final class HTMLUtils {
  
    private HTMLUtils() {}
  
    /** The DTD name. */
    public static final String dtdNameForHTMLParser = "html32.bdtd";
  
    private static DTD dtdForHTMLParser = null;
  
    /**
     * Add an Element to the ContentModel.
     * @param cm the ContentModel to add to
     * @param existing existing element
     * @param alt alternate element
     */
    public static void add(ContentModel cm, Element existing, Element alt) {
      if (cm.content == existing) {
        ContentModel twig =
            new ContentModel(0, existing, new ContentModel(0, alt, null));
        if (cm.type == 0) {
          cm.type = '|';
          cm.content = twig;
        }
        else
          cm.content = new ContentModel('|', twig);
      }
      else if (cm.content instanceof ContentModel)
        add((ContentModel)cm.content, existing, alt);
  
      if (cm.next != null)
        add(cm.next, existing, alt);
    }
  
    /**
    * Add element to a DTD.
    * @param dtd DTD to add to 
    * @param existing existing element
    * @param alt alternate element
    */
   public static void addToContentModels(DTD dtd,
                                         Element existing, Element alt) {
     for (Enumeration<Element> els = dtd.elementHash.elements();
          els.hasMoreElements();) {
       ContentModel c = ((Element)els.nextElement()).content;
       if (c != null)
         add(c, existing, alt);
     }
   }
 
   /**
    * @return a DTD
    */
   public static DTD dtdForHTMLParser() {
     // not clear HTF this putDTDHash/getDTD API is meant to be useful ...
 
     if (dtdForHTMLParser == null)
       try {
         dtdForHTMLParser = DTD.getDTD(dtdNameForHTMLParser);
         InputStream res = dtdForHTMLParser.getClass().
                               getResourceAsStream(dtdNameForHTMLParser);
         if (res == null)
           throw new FileNotFoundException(
               "Resource " + dtdNameForHTMLParser + " not found: " +
               "but it ought to be in rt.jar?!");
         dtdForHTMLParser.read(new DataInputStream(res));
 
         // add <SPAN CLASS=...> with the same content model as <DIV>
         // [which is a hack for bibliomania!!]
         // usable in the same places as <I>
 
         Element div = (Element)dtdForHTMLParser.elementHash.get("div");
         Element i = (Element)dtdForHTMLParser.elementHash.get("i");
 
         dtdForHTMLParser.defineElement(
            "span", DTDConstants.STARTTAG, false, false, div.content, null, null,
            new AttributeList("class", DTDConstants.CDATA,
                              0, null, null, null));
 
         Element span = (Element)dtdForHTMLParser.elementHash.get("span");
 
         addToContentModels(dtdForHTMLParser, i, span);
       }
       catch (Exception e) {
         throw new UnexpectedExceptionException(
           "making the DTD for Sun's HTML parser", e);
       }
 
     return dtdForHTMLParser;
   }
 
   /**
    * If the given character has special meaning in HTML or will not
    * necessarily encode in the character set, then return an escape string.
    * <p>
    * The name of this method implies the character is escaped as a
    * character entity but if the second argument is true then newlines
    * are encoded as &lt;BR&gt;.
    * This is not required for attribute values.
    * <p>
    * Which characters will necessarily encode depends on the charset.
    * For backward compatibility if a charset is not passed we assume the
    * character will encode.
    * If a charset is passed and a character does not encode then we
    * replace it with a numeric character reference (not an entity
    * either but pretty similar).
    *
    * @param c character to lookup entity for 
    * @param mapBR whether to replace line ends
    * @param ce an encoder
    * @param markup whether string contains markup 
    * @return an entity or null
    */
   public static String entityFor(char c, boolean mapBR, CharsetEncoder ce, boolean markup) {
     switch (c) {
       case '\n': return mapBR && !markup ? "<BR>\n" : null;
       case '<' : return markup ? null : "&lt;" ;
       case '>' : return markup ? null : "&gt;" ;
       case '&' : return markup ? null : "&amp;" ;
       // Unicode and ISO 8859-1
 
       case 163 : return "&pound;" ;
       case 192 : return "&Agrave;" ;
       case 193 : return "&Aacute;" ;
       case 194 : return "&Acirc;" ;
       case 199 : return "&Ccedil;" ;
       case 200 : return "&Egrave;" ;
       case 201 : return "&Eacute;" ;
       case 202 : return "&Ecirc;" ;
       case 204 : return "&Igrave;" ;
       case 205 : return "&Iacute;" ;
       case 206 : return "&Icirc;" ;
       case 210 : return "&Ograve;" ;
       case 211 : return "&Oacute;" ;
       case 212 : return "&Ocirc;" ;
       case 217 : return "&Ugrave;" ;
       case 218 : return "&Uacute;" ;
       case 219 : return "&Ucirc;" ;
       case 224 : return "&agrave;" ;
       case 225 : return "&aacute;" ;
       case 226 : return "&acirc;" ;
       case 228 : return "&auml;" ;
       case 231 : return "&ccedil;" ;
       case 232 : return "&egrave;" ;
       case 233 : return "&eacute;" ;
       case 234 : return "&ecirc;" ;
       case 236 : return "&igrave;" ;
       case 237 : return "&iacute;" ;
       case 238 : return "&icirc;" ;
       case 242 : return "&ograve;" ;
       case 243 : return "&oacute;" ;
       case 244 : return "&ocirc;" ;
       case 249 : return "&ugrave;" ;
       case 250 : return "&uacute;" ;
       case 251 : return "&ucirc;" ;
       case 252 : return "&uuml;" ;
       
       
       case '"' : return markup ? null : "&quot;";
       case '\'': return markup ? null : "&#39;";
       default:
         if (ce == null || ce.canEncode(c)) {
           return null;  
         } else {
           String result = "&#x" + Integer.toHexString(c) + ";";
           //System.err.println("Cannot encode: " + c + " so encoded as: " + result);
           return result;
         }
     }
   }
 
   /**
    * Return the String with all high value ASCII characters 
    * replaced with HTML entities.
    * 
    * @param s input String
    * @param mapBR whether to replace line ends with html breaks
    * @param encoding the encoding of the input string
    * @param markup whether string is an sgml fragment
    * @return the input with appropriate substitutions
    */
   public static String entitied(String s, boolean mapBR, String encoding, boolean markup) {
     int length = s.length();
     int i;
     String entity = null;
 
     CharsetEncoder ce = null;
     if (encoding != null) {
       ce = Charset.forName(encoding).newEncoder();
     }
 
     for (i = 0;
          i < length && (entity = entityFor(s.charAt(i), mapBR, ce, markup)) == null;
          ++i);
 
     if (entity == null) return s;
 
     StringBuffer b = new StringBuffer(length * 2);
     for (int j = 0; j < i; ++j)
       b.append(s.charAt(j));
 
     b.append(entity);
 
     char c;
     for (++i; i < length; ++i) {
       c = s.charAt(i);
       entity = entityFor(c, mapBR, ce, markup);
       if (entity != null) {
         b.append(entity);
       } else
         b.append(c);
     }
     return b.toString();
   }
 
   /**
    * Escape the given string as PCDATA without regard for any characters that
    * cannot be encoded in some required character set.
    * <p>
    * This is for backward compatibility as it is used below.
    *
    * @param s the String to replace special characters from
    * @return a new String with special characters replaced with entities
    * @see #entitied(String, boolean, String, boolean)
    */
   public static String entitied(String s) {
     return entitied(s, true, null, false);
   }
 
   /**
    * Javascript escape sequence for a character, if any, 
    * otherwise null.
    * @param c the character
    * @return an escape sequence or null
    */
   public static String jsEscapeFor(char c) {
     switch (c) {
       case '\n': return "\\012";
       case '"': return "\\042";
       case '\'': return "\\047";
       default: return null;
     }
   } 
 
   /**
    * Javascript escape a String.
    * @param s the String to escape
    * @return the escaped String
    */
   public static String jsEscaped(String s) {
     int length = s.length();
     int i = 0;
     String escape = null;
     for (i = 0; i < length && (escape = jsEscapeFor(s.charAt(i))) == null; ++i);
 
     if (escape == null) return s;
 
     StringBuffer b = new StringBuffer(length * 2);
     for (int j = 0; j < i; ++j)
       b.append(s.charAt(j));
 
     b.append(escape);
 
     char c;
     for (++i; i < length; ++i) {
       c = s.charAt(i);
       escape = jsEscapeFor(c);
       if (escape != null)
         b.append(escape);
       else
         b.append(c);
     }
     return b.toString();
   }
 
   /**
    * Write a tag to a Writer.
    * @param w the Writer to write to
    * @param tag the Tag to write
    * @param attributes the Tag's attributes
    * @throws IOException if there is a problem writing
    */
   public static void write(Writer w, HTML.Tag tag, AttributeSet attributes)
       throws IOException {
     w.write('<');
     w.write(tag.toString());
     for (Enumeration<?> a = attributes.getAttributeNames();
          a.hasMoreElements();) {
       Object n = a.nextElement();
       if (attributes.isDefined(n)) {
         w.write(' ');
         w.write(n.toString());
         w.write("=\"");
         w.write(entitied(attributes.getAttribute(n).toString()));
         w.write('"');
       }
     }
     w.write('>');
   }
 
   /**
    * @param tag the Tag
    * @param attributes the Tag's attributes
    * @return a String version of the Tag
    */
   public static String stringOf(HTML.Tag tag, AttributeSet attributes) {
     StringWriter w = new StringWriter();
 
     try {
       write(w, tag, attributes);
     }
     catch (IOException e) {
       throw new UnexpectedExceptionException(e);
     }
 
     return w.toString();
   }
 
 /**
  * An Instance of a tag.
  */
   public static class TagInstance {
     /** The tag. */
     public final HTML.Tag tag;
     /** Its attributes. */
     public final AttributeSet attributes;
 
     /** Constructor. */
     public TagInstance(HTML.Tag tag, AttributeSet attributes) {
       this.tag = tag;
       this.attributes = attributes;
     }
 
     /**
      * Write tag to specified Writer. 
      * @param w The Writer to write to.
      */
     public void write(Writer w) throws IOException {
       HTMLUtils.write(w, tag, attributes);
     }
 
     /** A String representation. 
      * {@inheritDoc}
      * @see java.lang.Object#toString()
      */
     public String toString() {
       return HTMLUtils.stringOf(tag, attributes);
     }
   }
 }