/***
 * Copyright (c) 2009 Caelum - www.caelum.com.br/opensource
 * All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * 	http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package br.com.caelum.vraptor.http.ognl;

import java.lang.reflect.Array;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import br.com.caelum.vraptor.VRaptorException;
import br.com.caelum.vraptor.ioc.RequestScoped;

/**
 * A component capable of removing null elements out of collections and arrays.
 *
 * @author guilherme silveira
 */
@RequestScoped
public class EmptyElementsRemoval {

	private final Set<Collection<?>> collections = new HashSet<Collection<?>>();
	private final Map<SetValue, Object> arrays = new HashMap<SetValue, Object>();

	class SetValue {
		private final Method method;
		private final Object instance;

		public SetValue(Object instance, Method setter) {
			this.instance = instance;
			this.method = setter;
		}

		void set(Object newValue) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
			method.invoke(instance, newValue);
			arrays.put(this, newValue);
		}

		@Override
		public boolean equals(Object obj) {
			if (!(obj instanceof SetValue)) {
				return false;
			}
			SetValue other = (SetValue) obj;
			return method.equals(other.method) && instance.equals(other.instance);
		}

		@Override
		public int hashCode() {
			return method.hashCode();
		}
	}

	public void removeExtraElements() {
		for (Collection<?> collection : collections) {
			for (Iterator<?> iterator = collection.iterator(); iterator.hasNext();) {
				Object object = iterator.next();
				if (object == null) {
					iterator.remove();
				}
			}
		}
		collections.clear();
		for (Map.Entry<SetValue, Object> setValueObjectEntry : arrays.entrySet()) {
			Object array = setValueObjectEntry.getValue();
			Object newArray = removeNullsFromArray(array);
			try {
				setValueObjectEntry.getKey().set(newArray);
			} catch (InvocationTargetException e) {
				throw new VRaptorException(e.getCause());
			} catch (Exception e) {
				throw new IllegalArgumentException(e);
			}
		}
		arrays.clear();
	}

	public Object removeNullsFromArray(Object array) {
		int length = Array.getLength(array);
		int total = length;
		for (int i = 0; i < length; i++) {
			if (Array.get(array, i) == null) {
				total--;
			}
		}
		Object newArray = Array.newInstance(array.getClass().getComponentType(), total);
		int actual = 0;
		for (int i = 0; i < length; i++) {
			Object value = Array.get(array, i);
			if (value != null) {
				Array.set(newArray, actual++, value);
			}
		}
		return newArray;
	}

	public void add(Collection<?> collection) {
		this.collections.add(collection);
	}

	public void add(Object array, Method setter, Object instance) {
		this.arrays.put(new SetValue(instance, setter), array);
	}

}