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/*
 * Copyright © 2005-2008 GlobalMentor, Inc. 
 *
 * 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 io.guise.framework.component;

import java.io.IOException;
import java.util.*;

import io.guise.framework.model.InfoModel;

import static java.util.Collections.*;
import static java.util.Objects.*;

/**
 * A composite component that represents the state of its child components.
 * @param  The type of object being represented.
 * @param  The component state of each object.
 * @author Garret Wilson
 */
public abstract class AbstractCompositeStateComponent extends AbstractMultipleCompositeComponent //TODO fire events when component states are added or removed so that AJAX updates can be sent
{

	/** The map of component state for each object. */
	private final Map componentStateMap = synchronizedMap(new HashMap());

	/** @return An iterable of component states. */
	protected Iterable getComponentStates() {
		synchronized(componentStateMap) { //don't allow the map to be modified while we access it
			return new ArrayList(componentStateMap.values()); //copy the component state values and return them
		}
	}

	/**
	 * Retrieves a component state for the given object.
	 * @param object The object for which a representation component should be returned.
	 * @return The state of the child component to represent the given object, or null if there is no component for the given object.
	 */
	protected S getComponentState(final T object) {
		return componentStateMap.get(object); //get the component state keyed to this object
	}

	/**
	 * Retrieves a component state for the given object. If no component yet exists for the given object, one will be created.
	 * @param object The object for which a representation component should be returned.
	 * @return The state of the child component to represent the given object.
	 * @throws IllegalArgumentException if the given object is not an appropriate object for a component state to be created.
	 * @see #getComponentState(Object)
	 * @see #createComponentState(Object)
	 * @see #putComponentState(Object, io.guise.framework.component.AbstractCompositeStateComponent.ComponentState)
	 */
	protected S determineComponentState(final T object) {
		S componentState; //we'll find a component state and store it here
		synchronized(componentStateMap) { //don't allow the map to be modified while we access it
			componentState = getComponentState(object); //get the component state for this object
			if(componentState == null) { //if there is no component state
				componentState = createComponentState(object); //create a new component state for the object
				putComponentState(object, componentState); //store the component state in the map for next time			
			}
		}
		return componentState; //return the component state
	}

	/**
	 * Stores a child component state for the given object. The component's theme will be updated immediately, as the component state is likely to be generated
	 * dynamically during component view update.
	 * @param object The object with which the component state is associated.
	 * @param componentState The child component state to represent the given object, or null if there is no component for the given object.
	 * @return The child component that previously represented the given tree node, or null if there was previously no component for the given
	 *         object.
	 * @see Component#updateTheme()
	 */
	protected S putComponentState(final T object, final S componentState) {
		final S oldComponentState = componentStateMap.put(object, componentState); //associate the component state with this object
		if(oldComponentState != null) { //if there was a component state before
			removeComponent(oldComponentState.getComponent()); //remove the old component from the set of components
		}
		final Component component = componentState.getComponent(); //get the component state
		addComponent(component); //put the new component in the component set
		try {
			component.updateTheme(); //make sure the theme is applied to the compnent
		} catch(final IOException ioException) { //if there is a problem initializing the properties
			throw new IllegalStateException(ioException); //TODO improve error
		}
		return oldComponentState; //return whatever component state was previously in the map
	}

	/**
	 * Removes the child component state for the given object.
	 * @param object The object with which the representation component is associated.
	 * @return The child component state that previously represented the given object, or null if there was previously no component for the given
	 *         object.
	 */
	protected ComponentState removeComponentState(final T object) {
		final ComponentState oldComponentState = componentStateMap.remove(object); //remove the component state associated with this object
		if(oldComponentState != null) { //if there was a component state before
			removeComponent(oldComponentState.getComponent()); //remove the old component from the set of components
		}
		return oldComponentState; //return whatever component state was previously in the map
	}

	/** Removes all child component states. */
	protected void clearComponentStates() { //TODO make sure this and related routines doesn't leak components or component states
		for(final Component component : getChildComponents()) { //for each component in the container
			removeComponent(component); //remove this component
		}
		componentStateMap.clear(); //remove all component states
	}

	/**
	 * Retrieves the component for the given object. If no component yet exists for the given object, one will be created.
	 * @param object The object for which a representation component should be returned.
	 * @return The child component representing the given object.
	 * @throws IllegalArgumentException if the given object is not an appropriate object for a component to be created.
	 */
	protected Component getComponent(final T object) {
		return determineComponentState(object).getComponent(); //get the component stored in the component state, creating one if needed
	}

	/**
	 * Retrieves the object for the given component.
	 * @param component The child component representing an object.
	 * @return The object the child component represents.
	 * @throws NullPointerException if the given component is null.
	 * @throws IllegalArgumentException if the given component does not represent any object.
	 */
	protected T getObject(final Component component) {
		requireNonNull(component, "Component cannot be null.");
		synchronized(componentStateMap) { //don't allow the map to be modified while we access it
			for(final Map.Entry componentStateEntry : componentStateMap.entrySet()) { //for all the map entries
				if(componentStateEntry.getValue().getComponent() == component) { //if we found the component
					return componentStateEntry.getKey(); //return the object being represented
				}
			}
		}
		throw new IllegalArgumentException("Component " + component + " not representing any object.");
	}

	/**
	 * Info model constructor.
	 * @param infoModel The component info model.
	 * @throws NullPointerException if the given info model is null.
	 */
	public AbstractCompositeStateComponent(final InfoModel infoModel) {
		super(infoModel); //construct the parent class
	}

	/**
	 * Creates a component state to represent the given object.
	 * @param object The object with which the component state is to be associated.
	 * @return The component state to represent the given object.
	 * @throws IllegalArgumentException if the given object is not an appropriate object for a component state to be created.
	 */
	protected abstract S createComponentState(final T object);

	/**
	 * An encapsulation of the state of a representation component.
	 * @author Garret Wilson
	 */
	protected abstract static class ComponentState {

		/** The representation component. */
		private final Component component;

		/** @return The representation component. */
		public Component getComponent() {
			return component;
		}

		/**
		 * Constructor
		 * @param component The representation component.
		 * @throws NullPointerException if the given component is null.
		 */
		public ComponentState(final Component component) {
			this.component = requireNonNull(component, "Component cannot be null.");
		}
	}

}




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