/*
 * Copyright (c) 2007, Rickard Öberg. 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 org.apache.zest.bootstrap;

import org.apache.zest.api.Qi4j;
import org.apache.zest.api.activation.ActivationException;
import org.apache.zest.api.structure.Application;
import org.apache.zest.api.structure.Module;

/**
 * Base class for Assembler that creates an Application
 * with one Layer and one Module. Create a subclass of this
 * and implement the {@link Assembler#assemble(ModuleAssembly)} method.
 * Once the SingletonAssembler is instantiated it will have created and activated
 * an Application which can be accessed from {@link org.apache.zest.bootstrap.SingletonAssembler#application()}.
 * You can also easily access any resources specific for the single Module, such as the TransientBuilderFactory.
 */
public abstract class SingletonAssembler
    implements Assembler
{
    private Energy4Java qi4j;
    private Application applicationInstance;
    private final Module moduleInstance;

    /**
     * Creates a Zest Runtime instance containing one Layer with one Module.
     * The Layer will be named "Layer 1" and the Module will be named "Module 1". It is possible to add
     * additional layers and modules via the Assembler interface that must be implemented in the subclass of this
     * class.
     *
     * @throws AssemblyException Either if the model can not be created from the disk, or some inconsistency in
     *                           the programming model makes it impossible to create it.
     * @throws ActivationException If the automatic {@code activate()} method is throwing this Exception..
     */
    public SingletonAssembler()
        throws AssemblyException, ActivationException
    {
// START SNIPPET: actual
        qi4j = new Energy4Java();
        applicationInstance = qi4j.newApplication( new ApplicationAssembler()
        {
            @Override
            public ApplicationAssembly assemble( ApplicationAssemblyFactory applicationFactory )
                throws AssemblyException
            {
                return applicationFactory.newApplicationAssembly( SingletonAssembler.this );
            }
        } );

        try
        {
            beforeActivation( applicationInstance );
            applicationInstance.activate();
        }
        catch( Exception e )
        {
            if( e instanceof ActivationException )
            {
                throw ( (ActivationException) e );
            }
            throw new ActivationException( "Could not activate application", e );
        }
// START SNIPPET: actual

        moduleInstance = applicationInstance.findModule( "Layer 1", "Module 1" );
    }

    public final Qi4j runtime()
    {
        return qi4j.spi();
    }

    public final Application application()
    {
        return applicationInstance;
    }

    public final Module module()
    {
        return moduleInstance;
    }

    protected void beforeActivation( Application application )
        throws Exception
    {
    }
}