/*******************************************************************************
 * Copyright (c) 2007, 2010 Association for Decentralized Information Management
 * in Industry THTH ry.
 * 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:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/
package org.simantics.g2d.canvas.impl;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import org.simantics.g2d.canvas.ICanvasParticipant;
import org.simantics.g2d.diagram.handler.DiagramHandler;

/**
 * @author Toni Kalajainen
 */
public class DependencyReflection {

	private final static ReferenceDefinition[] EMPTY = new ReferenceDefinition[0]; 
	
	@Retention(RetentionPolicy.RUNTIME)
	@Target(ElementType.FIELD)
	public static @interface Dependency {}
	@Retention(RetentionPolicy.RUNTIME)
	@Target(ElementType.FIELD)
	public static @interface Reference {}
	
	/**
	 * Scans an object with reflection for all dependencies 
	 * <p>
	 * Example:
	 * 
	 * @Dependency
	 * ViewportInteractor vi;
	 * 
	 * @param obj object to scan
	 * @return an array of painters and their priorities
	 */
	public static ReferenceDefinition[] getDependencies(final Object obj, ReferenceType type)
	{
		List<ReferenceDefinition> result = new ArrayList<ReferenceDefinition>();
		Class<?> clazz = obj.getClass();
		_addDependencies(clazz, result, type);
		//if (result==null) return EMPTY;
		return result.toArray(EMPTY);
	}

    private static void _addDependencies(Class<?> clazz, Collection<ReferenceDefinition> result, ReferenceType type)
	{
		for (final Field f : clazz.getDeclaredFields()) {
			Class<?> c = f.getType();
			Dependency dep = (Dependency) f.getAnnotation(Dependency.class);
			Reference ref = (Reference) f.getAnnotation(Reference.class);
			if (dep==null && ref==null) continue;
			ReferenceType referenceType = null;			
			if ( ICanvasParticipant.class.isAssignableFrom( c ) )
				referenceType = ReferenceType.CanvasParticipant;
			else if ( DiagramHandler.class.isAssignableFrom( c ) )
				referenceType = ReferenceType.DiagramHandler;
			else assert(false);
			if (referenceType!=type) continue;
			
			assert(!(dep!=null && ref!=null));
			ReferenceDefinition rd = new ReferenceDefinition();
			rd.dependency = dep!=null;
			rd.field = f;
			rd.requirement = c;
			rd.referenceType = referenceType;
			
			f.setAccessible(true);
			result.add(rd);
		}
		Class<?> superClass = clazz.getSuperclass();
		if (superClass!=null)
			_addDependencies(superClass, result, type);
	}
	
	public final static class ReferenceDefinition {
		public Class<?> requirement;
		public Field field;
		public boolean dependency;
		public ReferenceType referenceType; 
	}	
	
	public static enum ReferenceType {
		CanvasParticipant, DiagramHandler
	}
	
}