/*
 * XmlReader.java
 * Copyright (C) 1999,2000,2001 The Free Software Foundation
 * 
 * This file is part of GNU JAXP, a library.
 *
 * GNU JAXP is free software; you can redistribute it and/or modify
 * it under the terms of 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.
 * 
 * GNU JAXP 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.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Linking this library statically or dynamically with other modules is
 * making a combined work based on this library.  Thus, the terms and
 * conditions of the GNU General Public License cover the whole
 * combination.
 *
 * As a special exception, the copyright holders of this library give you
 * permission to link this library with independent modules to produce an
 * executable, regardless of the license terms of these independent
 * modules, and to copy and distribute the resulting executable under
 * terms of your choice, provided that you also meet, for each linked
 * independent module, the terms and conditions of the license of that
 * module.  An independent module is a module which is not derived from
 * or based on this library.  If you modify this library, you may extend
 * this exception to your version of the library, but you are not
 * obliged to do so.  If you do not wish to do so, delete this
 * exception statement from your version. 
 */

package gnu.xml.aelfred2;

import java.io.IOException;
import java.util.Locale;

import org.xml.sax.*;
import org.xml.sax.ext.*;

import gnu.xml.pipeline.EventFilter;
import gnu.xml.pipeline.ValidationConsumer;


/**
 * This SAX2 parser optionally layers a validator over the &AElig;lfred2
 * SAX2 parser.  While this will not evaluate every XML validity constraint,
 * it does support all the validity constraints that are of any real utility
 * outside the strict SGML-compatible world.  See the documentation for the
 * SAXDriver class for information about the SAX2 features and properties
 * that are supported, and documentation for the ValidationConsumer for
 * information about what validity constraints may not be supported.
 * (&AElig;lfred2 tests some of those, even in non-validating mode, to
 * achieve better conformance.)
 *
 * <p> Note that due to its internal construction, you can't change most
 * handlers until parse() returns.  This diverges slightly from SAX, which
 * expects later binding to be supported.  Early binding involves less
 * runtime overhead, which is an issue for event pipelines as used inside
 * this parser.  Rather than relying on the parser to handle late binding
 * to your own handlers, do it yourself.
 *
 * @see SAXDriver
 * @see gnu.xml.pipeline.ValidationConsumer
 *
 * @author David Brownell
 */
public final class XmlReader implements XMLReader
{
    private SAXDriver		aelfred2 = new SAXDriver ();
    private EventFilter		filter = new EventFilter ();
    private boolean		isValidating;
    private boolean		active;


    /** Constructs a SAX Parser.  */
    public XmlReader ()
	{ }

    /**
     * Constructs a SAX Parser, optionally treating validity errors
     * as if they were fatal errors.
     */
    public XmlReader (boolean invalidIsFatal)
    {
	if (invalidIsFatal)
	    setErrorHandler (new DefaultHandler2 () {
		public void error (SAXParseException e)
		throws SAXException
		    { throw e; }
		});
    }

    /**
     * <b>SAX2</b>: Returns the object used to report the logical
     * content of an XML document.
     */
    public ContentHandler getContentHandler ()
	{ return filter.getContentHandler (); }

    /**
     * <b>SAX2</b>: Assigns the object used to report the logical
     * content of an XML document.
     * @exception IllegalStateException if called mid-parse
     */
    public void setContentHandler (ContentHandler handler)
    {
	if (active)
	    throw new IllegalStateException ("already parsing");
	filter.setContentHandler (handler);
    }

    /**
     * <b>SAX2</b>: Returns the object used to process declarations related
     * to notations and unparsed entities.
     */
    public DTDHandler getDTDHandler ()
	{ return filter.getDTDHandler (); }

    /**
     * <b>SAX1</b> Assigns DTD handler
     * @exception IllegalStateException if called mid-parse
     */
    public void setDTDHandler (DTDHandler handler)
    {
	if (active)
	    throw new IllegalStateException ("already parsing");
	filter.setDTDHandler (handler);
    }

    /**
     * <b>SAX2</b>: Returns the object used when resolving external
     * entities during parsing (both general and parameter entities).
     */
    public EntityResolver getEntityResolver ()
	{ return aelfred2.getEntityResolver (); }

    /** <b>SAX1</b> Assigns parser's entity resolver */
    public void setEntityResolver (EntityResolver handler)
	{ aelfred2.setEntityResolver (handler); }

    /**
     * <b>SAX2</b>: Returns the object used to receive callbacks for XML
     * errors of all levels (fatal, nonfatal, warning); this is never null;
     */
    public ErrorHandler getErrorHandler ()
	{ return aelfred2.getErrorHandler (); }

    /**
     * <b>SAX1</b> Assigns error handler
     * @exception IllegalStateException if called mid-parse
     */
    public void setErrorHandler (ErrorHandler handler)
    {
	if (active)
	    throw new IllegalStateException ("already parsing");
	aelfred2.setErrorHandler (handler);
    }

    /**
     * <b>SAX2</b>:  Assigns the specified property.
     * @exception IllegalStateException if called mid-parse
     */
    public void setProperty (String propertyId, Object value)
    throws SAXNotRecognizedException, SAXNotSupportedException
    {
	if (active)
	    throw new IllegalStateException ("already parsing");
	if (getProperty (propertyId) != value)
	    filter.setProperty (propertyId, value);
    }

    /**
     * <b>SAX2</b>:  Returns the specified property.
     */
    public Object getProperty (String propertyId)
    throws SAXNotRecognizedException
    {
	if ((SAXDriver.PROPERTY + "declaration-handler")
			.equals (propertyId)
		|| (SAXDriver.PROPERTY + "lexical-handler")
			.equals (propertyId))
	    return filter.getProperty (propertyId);
	throw new SAXNotRecognizedException (propertyId);
    }

    private void forceValidating ()
    throws SAXNotRecognizedException, SAXNotSupportedException
    {
	aelfred2.setFeature (
	    SAXDriver.FEATURE + "namespace-prefixes",
	    true);
	aelfred2.setFeature (
	    SAXDriver.FEATURE + "external-general-entities",
	    true);
	aelfred2.setFeature (
	    SAXDriver.FEATURE + "external-parameter-entities",
	    true);
    }

    /**
     * <b>SAX2</b>:  Sets the state of features supported in this parser.
     * Note that this parser requires reporting of namespace prefixes when
     * validating.
     */
    public void setFeature (String featureId, boolean state)
    throws SAXNotRecognizedException, SAXNotSupportedException
    {
	boolean value = getFeature (featureId);

	if (state == value)
	    return;

	if ((SAXDriver.FEATURE + "validation").equals (featureId)) {
	    if (active)
		throw new SAXNotSupportedException ("already parsing");
	    if (state)
		forceValidating ();
	    isValidating = state;
	} else
	    aelfred2.setFeature (featureId, state);
    }

    /**
     * <b>SAX2</b>: Tells whether this parser supports the specified feature.
     * At this time, this directly parallels the underlying SAXDriver,
     * except that validation is optionally supported.
     *
     * @see SAXDriver
     */
    public boolean getFeature (String featureId)
    throws SAXNotRecognizedException, SAXNotSupportedException
    {
	if ((SAXDriver.FEATURE + "validation").equals (featureId))
	    return isValidating;

	return aelfred2.getFeature (featureId);
    }

    /**
     * <b>SAX1</b>: Sets the locale used for diagnostics; currently,
     * only locales using the English language are supported.
     * @param locale The locale for which diagnostics will be generated
     */
    public void setLocale (Locale locale)
    throws SAXException
	{ aelfred2.setLocale (locale); }

    /**
     * <b>SAX1</b>: Preferred API to parse an XML document, using a
     * system identifier (URI).
     */
    public void parse (String systemId)
    throws SAXException, IOException
    {
	parse (new InputSource (systemId));
    }

    /**
     * <b>SAX1</b>: Underlying API to parse an XML document, used
     * directly when no URI is available.  When this is invoked,
     * and the parser is set to validate, some features will be
     * automatically reset to appropriate values:  for reporting
     * namespace prefixes, and incorporating external entities.
     *
     * @param source The XML input source.
     *
     * @exception IllegalStateException if called mid-parse
     * @exception SAXException The handlers may throw any SAXException,
     *	and the parser normally throws SAXParseException objects.
     * @exception IOException IOExceptions are normally through through
     *	the parser if there are problems reading the source document.
     */
    public void parse (InputSource source)
    throws SAXException, IOException
    {
	EventFilter	next;
	boolean		nsdecls;

	synchronized (aelfred2) {
	    if (active)
		throw new IllegalStateException ("already parsing");
	    active = true;
	}

	// set up the output pipeline
	if (isValidating) {
	    forceValidating ();
	    next = new ValidationConsumer (filter);
	} else
	    next = filter;

	// connect pipeline and error handler
	// don't let _this_ call to bind() affect xmlns* attributes
	nsdecls = aelfred2.getFeature (
	    SAXDriver.FEATURE + "namespace-prefixes");
	EventFilter.bind (aelfred2, next);
	if (!nsdecls)
	    aelfred2.setFeature (
		SAXDriver.FEATURE + "namespace-prefixes",
		false);

	// parse, clean up
	try {
	    aelfred2.parse (source);
	} finally {
	    active = false;
	}
    }
}
