/*
 * @(#)$Id: SimpleState.java,v 1.9 2002/03/04 00:53:48 kk122374 Exp $
 *
 * Copyright 2001 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */
package com.sun.msv.reader;

import org.xml.sax.ContentHandler;
import org.xml.sax.helpers.NamespaceSupport;
import org.xml.sax.Attributes;
import org.xml.sax.Locator;
import org.xml.sax.helpers.AttributesImpl;
import org.xml.sax.helpers.LocatorImpl;
import com.sun.msv.util.StartTagInfo;

/**
 * base interface of the most of parsing states.
 * 
 * <p>
 * In this level of inheritance, contract is as follows.
 * 
 * <ol>
 *  <li>startElement(<x>) event is received by the parent state.
 *		It usually creates a child state by this event.
 * 
 *  <li>startSelf method of the child SimpleState is called.
 *		derived classes should perform necessary things
 *		by reading start tag information.
 * 
 *  <li>Whenever startElement method is received by
 *		SimpleState object, createChildState method is
 *		called to create a child state.
 *		Derived classes are responsible for providing
 *		appropriate child state objects.
 * 
 *  <li>Child state handles descendants. Usually, it finishes
 *		parsing when it sees endElement.
 * 
 *  <li>When endElement(</x>) event is received by this object,
 *		it calls endSelf method and reverts to the parent state.
 *		Derived classes are responsible for doing anything
 *		necessary within endSelf method.
 * </ol>
 * 
 * In other words, this state is only active for one hierarchy of XML elements
 * and derived classes are responsible for three abstract methods.
 * 
 * @author <a href="mailto:kohsuke.kawaguchi@eng.sun.com">Kohsuke KAWAGUCHI</a>
 */
public abstract class SimpleState extends State
{
	/** checks if this element belongs to the grammar. */
	protected boolean isGrammarElement( StartTagInfo tag ) {
		return reader.isGrammarElement(tag);
	}
	
	public void startElement( String namespaceURI, String localName, String qName, Attributes atts ) {
		final StartTagInfo tag = new StartTagInfo(
			namespaceURI,localName,qName,new AttributesImpl(atts),null);
		// we have to copy Attributes, otherwise it will be mutated by SAX parser
			
		if( isGrammarElement(tag) ) {
			// this is a grammar element.
			// creates appropriate child state for it.
			
			State nextState = createChildState(tag);
			if(nextState!=null) {
				reader.pushState(nextState,this,tag);
				return;
			}
            
			// unacceptable element
			reader.reportError(GrammarReader.ERR_MALPLACED_ELEMENT, tag.qName );
			// try to recover from error by just ignoring it.
		} else {
			// usually, foreign elements are silently ignored.
			// However, for the document element, we have to report an error
			if( parentState==null ) {
				reader.reportError(GrammarReader.ERR_MALPLACED_ELEMENT, tag.qName );
				// probably user is using a wrong namespace.
				reader.reportError(GrammarReader.WRN_MAYBE_WRONG_NAMESPACE, tag.namespaceURI );
			}
		}
		
		// element of a foreign namespace. skip subtree
		reader.pushState(new IgnoreState(),this,tag);
	}
	
	/** creates appropriate child state object for this element */
	abstract protected State createChildState( StartTagInfo tag );
	
		
	public final void endElement( String namespaceURI, String localName, String qName ) {
		// while processing endSelf, error should be reported for its start tag.
		Locator prevLoc = reader.locator;
		try {
			reader.locator = this.location;
			endSelf();
		} finally {
			reader.locator = prevLoc;
		}
		
		reader.popState();
	}
	
	public final void endDocument() {
        // top-level state receives endDocument event instead of endElement event.
		endSelf();
		reader.popState();
	}


	/**
	 * this method is called in endElement method
	 * when the state is about to be removed.
	 * 
	 * derived-class should perform any wrap-up job 
	 */
	protected void endSelf() {}
	
}