/*
 * JGrapes Event Driven Framework
 * Copyright (C) 2016-2018 Michael N. Lipp
 * 
 * This program is free software; you can redistribute it and/or modify it 
 * under the terms of the GNU Affero General Public License as published by 
 * the Free Software Foundation; either version 3 of the License, or 
 * (at your option) any later version.
 * 
 * This program 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 Affero General Public License 
 * for more details.
 * 
 * You should have received a copy of the GNU Affero General Public License along 
 * with this program; if not, see <http://www.gnu.org/licenses/>.
 */

package org.jgrapes.core.internal;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import org.jgrapes.core.Channel;
import org.jgrapes.core.ComponentType;
import org.jgrapes.core.Manager;
import org.jgrapes.core.NamedChannel;
import org.jgrapes.core.annotation.ComponentManager;
import org.jgrapes.core.annotation.Handler;

/**
 * The ComponentProxy is a special ComponentVertex that references the
 * object implementing the Component interface (instead of being
 * its base class).
 */
public final class ComponentProxy extends ComponentVertex {

    /** The reference to the actual component. */
    private final ComponentType component;
    /** The referenced component's channel. */
    private final Channel componentChannel;

    private static Field getManagerField(Class<?> clazz) {
        try {
            while (true) {
                for (Field field : clazz.getDeclaredFields()) {
                    if (Manager.class.isAssignableFrom(field.getType())
                        && field
                            .getAnnotation(ComponentManager.class) != null) {
                        return field;
                    }
                }
                clazz = clazz.getSuperclass();
                if (clazz == null) {
                    throw new IllegalArgumentException(
                        "Components must have a manager attribute");
                }
            }
        } catch (SecurityException e) {
            throw (RuntimeException) new IllegalArgumentException(
                "Cannot access component's manager attribute").initCause(e);
        }
    }

    private static Channel getComponentChannel(Field field) {
        ComponentManager cma = field.getAnnotation(ComponentManager.class);
        if (cma.channel() != Handler.NoChannel.class) {
            if (cma.channel() != Channel.BROADCAST.defaultCriterion()) {
                try {
                    return cma.channel().getConstructor().newInstance();
                } catch (InstantiationException // NOPMD
                        | IllegalAccessException | IllegalArgumentException
                        | InvocationTargetException | NoSuchMethodException
                        | SecurityException e) {
                    // Ignored
                }
            }
            return Channel.BROADCAST;
        }
        if (!cma.namedChannel().isEmpty()) {
            return new NamedChannel(cma.namedChannel());
        }
        return Channel.SELF;
    }

    /**
     * Create a new component proxy for the component and assign it to 
     * the specified field which must be of type {@link Manager}.
     * 
     * @param field the field that gets the proxy assigned
     * @param componentChannel the componen't channel
     * @param component the component
     */
    private ComponentProxy(
            Field field, ComponentType component, Channel componentChannel) {
        super(null);
        this.component = component;
        try {
            field.set(component, this);
            if (componentChannel == null) {
                componentChannel = getComponentChannel(field);
            }
            if (componentChannel.equals(Channel.SELF)) {
                componentChannel = this;
            }
            this.componentChannel = componentChannel;
            initComponentsHandlers();
        } catch (SecurityException | IllegalAccessException e) {
            throw (RuntimeException) new IllegalArgumentException(
                "Cannot access component's manager attribute").initCause(e);
        }
    }

    /**
     * Return the component node for a component that is represented
     * by a proxy in the tree.
     * 
     * @param component the component
     * @param componentChannel the component's channel
     * @return the node representing the component in the tree
     */
    @SuppressWarnings({ "PMD.DataflowAnomalyAnalysis",
        "PMD.AvoidAccessibilityAlteration", "PMD.ConfusingTernary" })
    /* default */ static ComponentVertex getComponentProxy(
            ComponentType component, Channel componentChannel) {
        ComponentProxy componentProxy;
        try {
            Field field = getManagerField(component.getClass());
            synchronized (component) {
                if (!field.canAccess(component)) {
                    field.setAccessible(true);
                    componentProxy = (ComponentProxy) field.get(component);
                    if (componentProxy == null) {
                        componentProxy = new ComponentProxy(
                            field, component, componentChannel);
                    }
                    field.setAccessible(false);
                } else {
                    componentProxy = (ComponentProxy) field.get(component);
                    if (componentProxy == null) {
                        componentProxy = new ComponentProxy(
                            field, component, componentChannel);
                    }
                }
            }
        } catch (SecurityException | IllegalAccessException e) {
            throw (RuntimeException) new IllegalArgumentException(
                "Cannot access component's manager attribute").initCause(e);
        }
        return componentProxy;
    }

    public ComponentType component() {
        return component;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.jgrapes.core.Manager#getChannel()
     */
    @Override
    public Channel channel() {
        return componentChannel;
    }

    /**
     * Return the object itself as value.
     */
    @Override
    public Object defaultCriterion() {
        return this;
    }

    /**
     * Matches the object itself (using identity comparison) or the
     * {@link Channel} class.
     * 
     * @see Channel#isEligibleFor(Object)
     */
    @Override
    @SuppressWarnings("PMD.CompareObjectsWithEquals")
    public boolean isEligibleFor(Object value) {
        return value.equals(Channel.class)
            || value == defaultCriterion();
    }
}