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/*
 * Copyright 2016 Agapsys Tecnologia Ltda-ME.
 *
 * 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 com.agapsys.web.toolkit;

/** Basic service implementation. */
public abstract class Service {

    private AbstractApplication app;

    final void throwIfNotActive() {
        if (!isActive())
            throw new RuntimeException("Instance is not active");
    }

    /**
     * Returns a boolean indicating if this instance was initialized.
     *
     * @return a boolean indicating if this instance was initialized.
     */
    public final boolean isActive() {
        synchronized(this) {
            return app != null;
        }
    }

    /**
     * Initializes this instance.
     *
     * @param app associated application.
     */
    final void _init(AbstractApplication app) {
        synchronized(this) {
            if (isActive())
                throw new IllegalStateException("Instance was already initialized");

            if (app == null)
                throw new IllegalArgumentException("Application cannot be null");

            this.app = app;
            onInit(app);
        }
    }

    /**
     * Called upon instance initialization. Default implementation does nothing.
     *
     * @param app associated application.
     */
    protected void onInit(AbstractApplication app) {}

    /**
     * Stops the instance.
     */
    final void _stop() {
        synchronized(this) {
            throwIfNotActive();

            onStop();

            this.app = null;
        }
    }

    /**
     * Actual instance shutdown code.
     *
     * Default implementation does nothing.
     */
    protected void onStop() {}

    /**
     * Return the application managing this instance.
     *
     * @return the application managing this instance.
     */
    public final AbstractApplication getApplication() {
        synchronized(this) {
            return app;
        }
    }

    /**
     * Returns a module registered in the same application as this instance is registered with.
     *
     * @param  Module type.
     * @param moduleClass module class.
     * @return module instance or null if given module class was not registered with associated application..
     */
    public final  M getModule(Class moduleClass) {
        synchronized(this) {
            throwIfNotActive();

            return app.getModule(moduleClass);
        }
    }

    /**
     * Returns a service instance.
     *
     * @param  Service type.
     * @param serviceClass service class.
     * @return service instance.
     */
    public final  S getService(Class serviceClass) {
        synchronized(this) {
            throwIfNotActive();

            return app.getService(serviceClass);
        }
    }

}