/*
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.tuscany.sca.host.embedded;

import java.lang.reflect.Constructor;

import org.apache.tuscany.sca.extensibility.ServiceDiscovery;
import org.apache.tuscany.sca.host.embedded.impl.DefaultSCADomain;
import org.apache.tuscany.sca.host.embedded.management.ComponentManager;
import org.osoa.sca.CallableReference;
import org.osoa.sca.ServiceReference;
import org.osoa.sca.ServiceRuntimeException;

/**
 * A handle to an SCA domain.
 * 
 * @version $Rev$ $Date$
 */
public abstract class SCADomain {
    
    static final String LOCAL_DOMAIN_URI = "http://localhost";

    /**
     * Static variable to hold the most recent instance of SCADomain
     */
    // TODO: Temporary support for SCADomain.connect() API
    protected static SCADomain theDomain;

    
    /**
     * Returns a new instance of a local SCA domain.
     *  
     * @return
     */
    public static SCADomain newInstance() {
        return createNewInstance(LOCAL_DOMAIN_URI, null);
    }
    
    /**
     * Returns a new instance of a local SCA domain. The specified deployable
     * composite will be included in the SCA domain.
     * 
     * @param composite the deployable composite to include in the SCA domain.
     * @return
     */
    public static SCADomain newInstance(String composite) {
        return createNewInstance(LOCAL_DOMAIN_URI, "/", composite);
    }
    
    /**
     * Returns a new instance of a local SCA domain. The specified deployable
     * composites will be included in the SCA domain.
     * 
     * @param domainURI the URI of the SCA domain
     * @param contributionLocation the location of an SCA contribution
     * @param composites the deployable composites to include in the SCA domain.
     * @return
     */
    public static SCADomain newInstance(String domainURI, String contributionLocation, String... composites) {
        return createNewInstance(domainURI, contributionLocation, composites);
    }

    /**
     * Removes the specified local SCA Domain instance
     * 
     * @param domainInstance the instance to be removed
     */
    // FIXME: Adding this as temporary support for the "connect" API
    public static void removeInstance(SCADomain domainInstance) {
        theDomain = null;
    }

    /**
     * Returns an SCADomain representing a remote SCA domain.
     * 
     * @param domainURI the URI of the SCA domain
     * @return
     */
    // FIXME : this is a temporary implementation to get the capability working
    public static SCADomain connect(String domainURI) {
        return theDomain;
    }

    /**
     * Close the SCA domain.
     */
    public void close() {
        // TODO: temporary to support initial SCADomain.connect capability
        SCADomain.removeInstance(this);
    }

    /**
     * Returns the URI of the SCA Domain.
     * 
     * @return the URI of the SCA Domain
     */
    public abstract String getURI();

    /**
     * Cast a type-safe reference to a CallableReference. Converts a type-safe
     * reference to an equivalent CallableReference; if the target refers to a
     * service then a ServiceReference will be returned, if the target refers to
     * a callback then a CallableReference will be returned.
     * 
     * @param target a reference proxy provided by the SCA runtime
     * @param <B> the Java type of the business interface for the reference
     * @param <R> the type of reference to be returned
     * @return a CallableReference equivalent for the proxy
     * @throws IllegalArgumentException if the supplied instance is not a
     *             reference supplied by the SCA runtime
     */
    public abstract <B, R extends CallableReference<B>> R cast(B target) throws IllegalArgumentException;

    /**
     * Returns a proxy for a service provided by a component in the SCA domain.
     * 
     * @param businessInterface the interface that will be used to invoke the
     *            service
     * @param serviceName the name of the service
     * @param <B> the Java type of the business interface for the service
     * @return an object that implements the business interface
     */
    public abstract <B> B getService(Class<B> businessInterface, String serviceName);

    /**
     * Returns a ServiceReference for a service provided by a component in the
     * SCA domain.
     * 
     * @param businessInterface the interface that will be used to invoke the
     *            service
     * @param serviceName the name of the service
     * @param <B> the Java type of the business interface for the service
     * @return a ServiceReference for the designated service
     */
    public abstract <B> ServiceReference<B> getServiceReference(Class<B> businessInterface, String serviceName);

    /**
     * Returns an SCADomain instance. If the system property
     * "org.apache.tuscany.sca.host.embedded.SCADomain" is set, its value is used as
     * the name of the implementation class. Otherwise, if the resource
     * "META-INF/services/org.apache.tuscany.sca.host.embedded.SCADomain" can be
     * loaded from the supplied ClassLoader. Otherwise, it will use
     * "org.apache.tuscany.sca.host.embedded.impl.DefaultSCADomain" as the default.
     * The named class is loaded from the supplied ClassLoader.
     * 
     * @param classLoader
     * @param domainURI
     * @param contributionLocation
     * @param composites
     * @return
     */
    static SCADomain createNewInstance(String domainURI, String contributionLocation, String... composites) {

        SCADomain domain = null;

        try {
            // Determine the runtime and application ClassLoader
            final ClassLoader runtimeClassLoader = SCADomain.class.getClassLoader();
            final ClassLoader applicationClassLoader = Thread.currentThread().getContextClassLoader();

            Class<?> implClass = ServiceDiscovery.getInstance().loadFirstServiceClass(SCADomain.class);

            if (implClass == null) {

                // Create a default SCA domain implementation
                domain =
                    new DefaultSCADomain(runtimeClassLoader, applicationClassLoader, domainURI, contributionLocation,
                                         composites);
            } else {

                // Create an instance of the discovered SCA domain implementation
                Constructor<?> constructor = null;
                try {
                    constructor =
                        implClass.getConstructor(ClassLoader.class,
                                                 ClassLoader.class,
                                                 String.class,
                                                 String.class,
                                                 String[].class);
                } catch (NoSuchMethodException e) {
                }
                if (constructor != null) {
                    domain =
                        (SCADomain)constructor.newInstance(runtimeClassLoader,
                                                           applicationClassLoader,
                                                           domainURI,
                                                           contributionLocation,
                                                           composites);
                } else {

                    constructor = implClass.getConstructor(ClassLoader.class, String.class);
                    domain = (SCADomain)constructor.newInstance(runtimeClassLoader, domainURI);
                }
            }

            // FIXME: temporary support for connect() API
            theDomain = domain;

            return domain;

        } catch (ServiceRuntimeException e) {
            throw e;
        } catch (Exception e) {
            throw new ServiceRuntimeException(e);
        }
    }

    public ComponentManager getComponentManager() {
        return null; 
    }

}