jsf/plugins/org.eclipse.jst.jsf.common/src/org/eclipse/jst/jsf/common/metadata/internal/provisional/query/SimpleMetaDataQueryVisitorImpl.java

/*******************************************************************************
 * Copyright (c) 2007 Oracle Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    Oracle - initial API and implementation
 *    
 ********************************************************************************/
package org.eclipse.jst.jsf.common.metadata.internal.provisional.query;

import java.util.Iterator;
import java.util.Stack;

import org.eclipse.jst.jsf.common.metadata.internal.provisional.Entity;
import org.eclipse.jst.jsf.common.metadata.internal.provisional.EntityGroup;
import org.eclipse.jst.jsf.common.metadata.internal.provisional.Trait;


/**
 * A simple metadata query visitor implementing {@link IEntityQueryVisitor} and {@link ITraitQueryVisitor}.
 * - simple find entity and traits by id only 	
 * - Does not allow for wild card searchs
 * API: extensibility?
 */
public class SimpleMetaDataQueryVisitorImpl implements IEntityQueryVisitor, ITraitQueryVisitor  {

	private String traitQuery;
	private SearchControl control;
	private boolean _stop;

	private EntityQueryComparator entityComparator;
	private SimpleResultSet/*<Entity>*/ entityResultSet;
	private SimpleResultSet/*<Trait>*/ traitResultSet;

	/**
	 * Constructor that also creates a default SearchControl
	 */
	public SimpleMetaDataQueryVisitorImpl() {
		super();
		control = new SearchControl();
	}
	
	/**
	 * Constructor
	 * @param control
	 */
	public SimpleMetaDataQueryVisitorImpl(SearchControl control) {
		super();
		this.control = control;
	}
	
	/* (non-Javadoc)
	 * @see org.eclipse.jst.jsf.common.metadata.internal.provisional.query.ITraitQueryVisitor#findTraits(org.eclipse.jst.jsf.common.metadata.internal.provisional.Entity, java.lang.String)
	 */
	public IResultSet/*<Trait>*/ findTraits(final Entity entity, final String traitQuery){
		
		resetQuery();
		if (entity != null){			
			this.traitQuery = traitQuery;			
			for (Iterator/*<Trait>*/ it=entity.getTraits().iterator();it.hasNext();){
				Trait t = (Trait)it.next();
				t.accept(this);
				if (stopVisiting())
					break;
			}
		}
		return getTraitResultSet();
	}

	/* (non-Javadoc)
	 * @see org.eclipse.jst.jsf.common.metadata.internal.provisional.query.ITraitVisitor#visit(org.eclipse.jst.jsf.common.metadata.internal.provisional.Trait)
	 */
	public void visit(Trait trait) {		
		if (trait.equals(traitQuery))
			getTraitResultSet().addItem(trait);		
		
		checkShouldStopVisitingTraits();
	}


	/* (non-Javadoc)
	 * @see org.eclipse.jst.jsf.common.metadata.internal.provisional.query.IEntityQueryVisitor#findEntities(org.eclipse.jst.jsf.common.metadata.internal.provisional.Entity, java.lang.String)
	 */
	public IResultSet/*<Entity>*/ findEntities(Entity initialEntityContext,
			String entityKey) {
		
		resetQuery();
		
		if (initialEntityContext != null){
			entityComparator = new EntityQueryComparator(entityKey);			
			initialEntityContext.accept(this);			
		}
		
		return getEntityResultSet();
	}

	private void resetQuery() {
		_stop = false;
	}

	/**
	 * @return @return lazy init of a SimpleResultSet of Entities
	 */
	private SimpleResultSet/*<Entity>*/ getEntityResultSet(){
		if (entityResultSet == null){
			entityResultSet = new SimpleResultSet/*<Entity>*/();
		}
		return entityResultSet;
	}

	/**
	 * @return lazy init of a SimpleResultSet of Traits
	 */
	private SimpleResultSet/*<Trait>*/ getTraitResultSet(){
		if (traitResultSet == null){
			traitResultSet = new SimpleResultSet/*<Trait>*/();
		}
		return traitResultSet;
	}
	
	/* (non-Javadoc)
	 * @see org.eclipse.jst.jsf.common.metadata.internal.provisional.query.IEntityVisitor#visit(org.eclipse.jst.jsf.common.metadata.internal.provisional.Entity)
	 */
	public void visit(Entity key) {		
		switch (entityComparator.compareTo(key)){
			case 0:
				getEntityResultSet().addItem(key);
				break;
			default:
				break;

		}
		checkShouldStopVisitingEntities();
	}
	/* (non-Javadoc)
	 * @see org.eclipse.jst.jsf.common.metadata.internal.provisional.query.IEntityVisitor#visitCompleted()
	 */
	public void visitCompleted() {
		entityComparator.popContext();
	}
	
	/* (non-Javadoc)
	 * @see org.eclipse.jst.jsf.common.metadata.internal.provisional.query.IMetaDataVisitor#stopVisiting()
	 */
	public boolean stopVisiting() {
		return _stop;
	}

	private void checkShouldStopVisitingEntities(){
		//implement how to set stop to signal to the entity accept() to skip visiting
		if (control.getCountLimit()== getEntityResultSet().size() && control.getCountLimit() != SearchControl.COUNT_LIMIT_NONE )
			_stop = true;
	}
	
	private void checkShouldStopVisitingTraits(){
		//this simple visitor will only find a single trait as it checks for exact match only currently 
		if (getTraitResultSet().size() > 0 )
			_stop = true;
	}


	/**
	 * Simple comparator that compares that an entity's id for with another
	 */
	private class EntityQueryComparator implements Comparable/*<Entity>*/{

		private String entityKey;
		private EntityStack stack;

		public EntityQueryComparator(String entityKey){
			this.entityKey = entityKey;		
			stack = new EntityStack();
		}
		
		public int compareTo(Object entity) {			
			stack.push(entity);
			return entityKey.compareTo(getRelativeId());			
		}
		
		public void popContext(){
			stack.pop();
		}
		
		private String getRelativeId(){
			int size = stack.size();
			int i = 1;
			StringBuffer buf = new StringBuffer();
			while(i < size){
				Entity e = (Entity)stack.elementAt(i);
				if (!(e instanceof EntityGroup)){
					if (buf.length()>0) 
						buf.append("/");
					buf.append(e.getId());
				}
				i++;
			}
			return buf.toString();
		}
	}
	
	/**
	 * Stack used for determining relative key of an entity from the initial context.
	 */
	private class EntityStack extends Stack/*<Entity>*/ {
		/**
         * 
         */
        private static final long serialVersionUID = -6010267544968175003L;

        public EntityStack(){
			super();
		}
	}

}