/*
 * @(#)DocumentParser.java	1.22 00/02/02
 *
 * Copyright 1998-2000 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */

package javax.swing.text.html.parser;

import javax.swing.text.SimpleAttributeSet;
import javax.swing.text.html.HTMLEditorKit;
import javax.swing.text.html.HTML;
import javax.swing.text.ChangedCharSetException;

import java.util.*;
import java.io.*;
import java.net.*;

import sun.io.*;

/**
 * A Parser for HTML Documents (actually, you can specify a DTD, but
 * you should really only use this class with the html dtd in swing).
 * Reads an InputStream of HTML and
 * invokes the appropriate methods in the ParserCallback class. This
 * is the default parser used by HTMLEditorKit to parse HTML url's.
 * <p>This will message the callback for all valid tags, as well as
 * tags that are implied but not explicitly specified. For example, the
 * html string (<p>blah) only has a p tag defined. The callback
 * will see the following methods:
 * <ol><li><i>handleStartTag(html, ...)</i></li>
 *     <li><i>handleStartTag(head, ...)</i></li>
 *     <li><i>handleEndTag(head)</i></li>
 *     <li><i>handleStartTag(body, ...)</i></li>
 *     <li>handleStartTag(p, ...)</i></li>
 *     <li>handleText(...)</li>
 *     <li><i>handleEndTag(p)</i></li>
 *     <li><i>handleEndTag(body)</i></li>
 *     <li><i>handleEndTag(html)</i></li>
 * </ol>
 * The items in <i>italic</i> are implied, that is, although they were not
 * explicitly specified, to be correct html they should have been present
 * (head isn't necessary, but it is still generated). For tags that
 * are implied, the AttributeSet argument will have a value of
 * <code>Boolean.TRUE</code> for the key
 * <code>HTMLEditorKit.ParserCallback.IMPLIED</code>.
 * <p>HTML.Attributes defines a type safe enumeration of html attributes.
 * If an attribute key of a tag is defined in HTML.Attribute, the
 * HTML.Attribute will be used as the key, otherwise a String will be used.
 * For example <p foo=bar class=neat> has two attributes. foo is
 * not defined in HTML.Attribute, where as class is, therefore the
 * AttributeSet will have two values in it, HTML.Attribute.CLASS with
 * a String value of 'neat' and the String key 'foo' with a String value of
 * 'bar'.
 * <p>The position argument will indicate the start of the tag, comment
 * or text. Similiar to arrays, the first character in the stream has a
 * position of 0. For tags that are
 * implied the position will indicate
 * the location of the next encountered tag. In the first example,
 * the implied start body and html tags will have the same position as the
 * p tag, and the implied end p, html and body tags will all have the same
 * position.
 * <p>As html skips whitespace the position for text will be the position
 * of the first valid character, eg in the string '\n\n\nblah'
 * the text 'blah' will have a position of 3, the newlines are skipped.
 * <p>
 * For attributes that do not have a value, eg in the html
 * string <code><foo blah></code> the attribute <code>blah</code>
 * does not have a value, there are two possible values that will be
 * placed in the AttributeSet's value:
 * <ul>
 * <li>If the DTD does not contain an definition for the element, or the
 *     definition does not have an explicit value then the value in the
 *     AttributeSet will be <code>HTML.NULL_ATTRIBUTE_VALUE</code>.
 * <li>If the DTD contains an explicit value, as in:
 *     <code><!ATTLIST OPTION selected (selected) #IMPLIED></code>
 *     this value from the dtd (in this case selected) will be used.
 * </ul>
 * <p>
 * Once the stream has been parsed, the callback is notified of the most
 * likely end of line string. The end of line string will be one of
 * \n, \r or \r\n, which ever is encountered the most in parsing the
 * stream.
 *
 * @version 	1.22 02/02/00
 * @author      Sunita Mani
 */
public class DocumentParser extends javax.swing.text.html.parser.Parser {

    private int inbody;
    private int intitle;
    private int inhead;
    private int instyle;
    private boolean seentitle;
    private HTMLEditorKit.ParserCallback callback = null;
    private boolean ignoreCharSet = false;
    private static final boolean debugFlag = false;

    public DocumentParser(DTD dtd) {
	super(dtd);
    }
 
    public void parse(Reader in,  HTMLEditorKit.ParserCallback callback, boolean ignoreCharSet) throws IOException {
	this.ignoreCharSet = ignoreCharSet;
	this.callback = callback;
	parse(in);
	// end of line
	callback.handleEndOfLineString(getEndOfLineString());
    }

    /**
     * Handle Start Tag.
     */
    protected void handleStartTag(TagElement tag) {

	Element elem = tag.getElement();
	if (elem == dtd.body) {
	    inbody++;
	} else if (elem == dtd.html) {
	} else if (elem == dtd.head) {
	    inhead++;
	} else if (elem == dtd.title) {
	    intitle++;
	} else if (elem == dtd.style) {
	    instyle++;
	}	
	if (debugFlag) {
	    if (tag.fictional()) {
		debug("Start Tag: " + tag.getHTMLTag() + " pos: " + getCurrentPos());
	    } else {
		debug("Start Tag: " + tag.getHTMLTag() + " attributes: " + 
		      getAttributes() + " pos: " + getCurrentPos());
	    }
	}
	if (tag.fictional()) {
	    SimpleAttributeSet attrs = new SimpleAttributeSet();
	    attrs.addAttribute(HTMLEditorKit.ParserCallback.IMPLIED,
			       Boolean.TRUE);
	    callback.handleStartTag(tag.getHTMLTag(), attrs,
				    getBlockStartPosition());
	} else {
	    callback.handleStartTag(tag.getHTMLTag(), getAttributes(),
				    getBlockStartPosition());
	    flushAttributes();
	}
    }


    protected void handleComment(char text[]) {
	if (debugFlag) {
	    debug("comment: ->" + new String(text) + "<-"
		  + " pos: " + getCurrentPos());
	}
	callback.handleComment(text, getBlockStartPosition());
    }

    /**
     * Handle Empty Tag.
     */
    protected void handleEmptyTag(TagElement tag) throws ChangedCharSetException {

	Element elem = tag.getElement();
	if (elem == dtd.meta && !ignoreCharSet) {
	    SimpleAttributeSet atts = getAttributes();
	    if (atts != null) {
		String content = (String)atts.getAttribute(HTML.Attribute.CONTENT);
		if (content != null) {
		    if ("content-type".equalsIgnoreCase((String)atts.getAttribute(HTML.Attribute.HTTPEQUIV))) {
			throw new ChangedCharSetException(content, false);
		    } else if ("charset" .equalsIgnoreCase((String)atts.getAttribute(HTML.Attribute.HTTPEQUIV))) {
			throw new ChangedCharSetException(content, true);
		    }
		}
	    }
	}
	if (inbody != 0 || elem == dtd.meta || elem == dtd.base || elem == dtd.isindex || elem == dtd.style || elem == dtd.link) {
	    if (debugFlag) {
		if (tag.fictional()) {
		    debug("Empty Tag: " + tag.getHTMLTag() + " pos: " + getCurrentPos());
		} else {
		    debug("Empty Tag: " + tag.getHTMLTag() + " attributes: " 
			  + getAttributes() + " pos: " + getCurrentPos());
		}
	    }
	    if (tag.fictional()) {
		SimpleAttributeSet attrs = new SimpleAttributeSet();
		attrs.addAttribute(HTMLEditorKit.ParserCallback.IMPLIED,
				   Boolean.TRUE);
		callback.handleSimpleTag(tag.getHTMLTag(), attrs,
					 getBlockStartPosition());
	    } else {
		callback.handleSimpleTag(tag.getHTMLTag(), getAttributes(),
					 getBlockStartPosition());
		flushAttributes();
	    }
	}
    }

    /**
     * Handle End Tag.
     */
    protected void handleEndTag(TagElement tag) {
	Element elem = tag.getElement();
	if (elem == dtd.body) {
	    inbody--;
	} else if (elem == dtd.title) {
	    intitle--;
	    seentitle = true;
	} else if (elem == dtd.head) {
            inhead--;
	} else if (elem == dtd.style) {
            instyle--;
	}
	if (debugFlag) {
	    debug("End Tag: " + tag.getHTMLTag() + " pos: " + getCurrentPos());
	}
	callback.handleEndTag(tag.getHTMLTag(), getBlockStartPosition());

    }

    /**
     * Handle Text.
     */
    protected void handleText(char data[]) {
	if (data != null) {
	    if (inbody != 0 || ((instyle != 0) ||
				((intitle != 0) && !seentitle))) {
		if (debugFlag) {
		    debug("text:  ->" + new String(data) + "<-" + " pos: " + getCurrentPos());
		}
		callback.handleText(data, getBlockStartPosition());
	    }
	}
    }

    /*
     * Error handling.
     */
    protected void handleError(int ln, String errorMsg) {
	if (debugFlag) {
	    debug("Error: ->" + errorMsg + "<-" + " pos: " + getCurrentPos());
	}
	/* PENDING: need to improve the error string. */
	callback.handleError(errorMsg, getCurrentPos());
    }


    /*
     * debug messages
     */
    private void debug(String msg) {
	System.out.println(msg);
    }
}