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/*
	Milyn - Copyright (C) 2008

	This library is free software; you can redistribute it and/or
	modify it under the terms of the GNU Lesser General Public
	License (version 2.1) as published by the Free Software
	Foundation.

	This library 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 Lesser General Public License for more details:
	http://www.gnu.org/licenses/lgpl.txt
*/
package org.milyn.yaml.handler;

import java.util.Stack;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.milyn.yaml.ElementNameFormatter;
import org.xml.sax.SAXException;
import org.yaml.snakeyaml.events.AliasEvent;
import org.yaml.snakeyaml.events.CollectionStartEvent;
import org.yaml.snakeyaml.events.Event;
import org.yaml.snakeyaml.events.ScalarEvent;
import org.yaml.snakeyaml.events.Event.ID;

/**
 * Takes a iterable yaml event stream and handles the events of the stream.
 *
 * @author maurice_zeijen
 */
public class YamlEventStreamHandler {

	private static Log logger = LogFactory.getLog(YamlEventStreamHandler.class);

    private static enum Type {
    	MAPPING,
    	SEQUENCE
    }

	private final ElementNameFormatter nameFormatter;

	private final String arrayElementName;

	private String documentName;

	public YamlEventStreamHandler(ElementNameFormatter nameFormatter, String documentName, String arrayElementName) {
		this.nameFormatter = nameFormatter;
		this.arrayElementName = arrayElementName;
		this.documentName = documentName;
	}

	public void handle(EventHandler eventHandler, Iterable yamlEventStream) throws SAXException {

		Stack elementNameStack = new Stack();
		Stack typeStack = new Stack();

		boolean isNextElementName = true;
		boolean outputStructAsElement = false;
		for (Event e : yamlEventStream) {

			if(logger.isTraceEnabled()) {
				logger.trace("Event: " + e);
			}

			if(e.is(ID.DocumentStart)) {
				elementNameStack.push(documentName);

				outputStructAsElement = true;
			} else if(e.is(ID.Scalar)) {
				ScalarEvent es = (ScalarEvent) e;

				if(isNextElementName && !lastTypeIsArray(typeStack)) {
					String name = nameFormatter.format(es.getValue());

					if(logger.isTraceEnabled()) {
		        		logger.trace("Element name: " + name);
		        	}

					elementNameStack.push(name);

					eventHandler.addNameEvent(es, name);

					isNextElementName = false;
				} else {
					String elementName = typeStack.peek() == Type.SEQUENCE ? arrayElementName : elementNameStack.pop();

		    		eventHandler.addValueEvent(es, elementName, es.getValue());

		    		isNextElementName = true;
				}
			} else if(e.is(ID.MappingStart) || e.is(ID.SequenceStart)) {
				CollectionStartEvent cse = (CollectionStartEvent) e;

				if(outputStructAsElement) {
					String elementName = lastTypeIsArray(typeStack) ? arrayElementName : elementNameStack.peek();
					eventHandler.startStructureEvent(cse, elementName);
				}

				typeStack.push(e.is(ID.SequenceStart) ? Type.SEQUENCE : Type.MAPPING);

				outputStructAsElement = true;
				isNextElementName = true;
			} else if(e.is(ID.MappingEnd) || e.is(ID.SequenceEnd)) {
				typeStack.pop();

				boolean typeStackPeekIsArray = lastTypeIsArray(typeStack);

				if(!elementNameStack.empty() && !typeStackPeekIsArray) {
					eventHandler.endStructureEvent(e, elementNameStack.pop());
				}

				if(typeStackPeekIsArray) {
					eventHandler.endStructureEvent(e, arrayElementName);
				}

			} else if(e.is(ID.Alias)) {
				String elementName = lastTypeIsArray(typeStack) ? arrayElementName : elementNameStack.pop();

				eventHandler.addAliasEvent((AliasEvent) e, elementName);

				isNextElementName = true;
			}

		}
	}

    private boolean lastTypeIsArray(Stack typeStack) {
    	return !typeStack.empty() && typeStack.peek() == Type.SEQUENCE;
    }


}