/*
 * JBoss, Home of Professional Open Source
 * Copyright 2010, Red Hat Inc., and individual contributors as indicated
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jboss.as.server.moduleservice;

import java.util.concurrent.CountDownLatch;

import org.jboss.as.server.Bootstrap;
import org.jboss.as.server.ServerLogger;
import org.jboss.as.server.ServerMessages;
import org.jboss.as.server.Services;
import org.jboss.modules.Module;
import org.jboss.modules.ModuleIdentifier;
import org.jboss.modules.ModuleLoadException;
import org.jboss.modules.ModuleLoader;
import org.jboss.modules.ModuleSpec;
import org.jboss.msc.service.AbstractServiceListener;
import org.jboss.msc.service.Service;
import org.jboss.msc.service.ServiceBuilder;
import org.jboss.msc.service.ServiceContainer;
import org.jboss.msc.service.ServiceController;
import org.jboss.msc.service.ServiceController.State;
import org.jboss.msc.service.ServiceName;
import org.jboss.msc.service.ServiceTarget;
import org.jboss.msc.service.StartContext;
import org.jboss.msc.service.StartException;
import org.jboss.msc.service.StopContext;
import org.jboss.msc.service.ValueService;
import org.jboss.msc.value.ImmediateValue;

/**
 * {@link ModuleLoader} that loads module definitions from msc services. Module specs are looked up in msc services that
 * correspond to the module names.
 * <p>
 * Modules are automatically removed when the corresponding service comes down.
 *
 * @author Stuart Douglas
 *
 */
public class ServiceModuleLoader extends ModuleLoader implements Service<ServiceModuleLoader> {

    // Provide logging
    private static final ServerLogger log = ServerLogger.MODULE_SERVICE_LOGGER;

    /**
     * Listener class that atomically retrieves the moduleSpec, and automatically removes the Module when the module spec
     * service is removed
     *
     * @author Stuart Douglas
     *
     */
    private class ModuleSpecLoadListener extends AbstractServiceListener<ModuleDefinition> {

        private final CountDownLatch latch = new CountDownLatch(1);
        private volatile StartException startException;
        private volatile ModuleSpec moduleSpec;

        private ModuleSpecLoadListener(ModuleIdentifier identifier) {
        }

        @Override
        public void listenerAdded(ServiceController<? extends ModuleDefinition> controller) {
            log.tracef("listenerAdded: %s", controller);
            State state = controller.getState();
            if (state == State.UP || state == State.START_FAILED) {
                done(controller, controller.getStartException());
            }
        }

        @Override
        public void transition(final ServiceController<? extends ModuleDefinition> controller, final ServiceController.Transition transition) {
            switch (transition) {
                case STARTING_to_UP:
                    log.tracef("serviceStarted: %s", controller);
                    done(controller, null);
                    break;
                case STARTING_to_START_FAILED:
                    log.tracef(controller.getStartException(), "serviceFailed: %s", controller);
                    done(controller, controller.getStartException());
                    break;
                case STOP_REQUESTED_to_STOPPING: {
                    log.tracef("serviceStopping: %s", controller);
                    ModuleSpec moduleSpec = this.moduleSpec;
                    ModuleIdentifier identifier = moduleSpec.getModuleIdentifier();
                    Module module = findLoadedModuleLocal(identifier);
                    if(module != null)
                        unloadModuleLocal(module);
                    // TODO: what if the service is restarted?
                    controller.removeListener(this);
                    break;
                }
            }
        }

        private void done(ServiceController<? extends ModuleDefinition> controller, StartException reason) {
            startException = reason;
            if (startException == null) {
                moduleSpec = controller.getValue().getModuleSpec();
            }
            latch.countDown();
        }

        public ModuleSpec getModuleSpec() throws ModuleLoadException {
            if (startException != null)
                throw new ModuleLoadException(startException.getCause());
            return moduleSpec;
        }
    }

    public static final ServiceName MODULE_SPEC_SERVICE_PREFIX = ServiceName.JBOSS.append("module", "spec", "service");

    public static final ServiceName MODULE_SERVICE_PREFIX = ServiceName.JBOSS.append("module", "service");

    public static final ServiceName MODULE_RESOLVED_SERVICE_PREFIX = ServiceName.of("module", "resolved", "service");


    public static final String MODULE_PREFIX = "deployment.";

    private final ModuleLoader mainModuleLoader;

    private volatile ServiceContainer serviceContainer;

    public ServiceModuleLoader(ModuleLoader mainModuleLoader) {
        this.mainModuleLoader = mainModuleLoader;
    }

    @Override
    protected Module preloadModule(final ModuleIdentifier identifier) throws ModuleLoadException {
        if (identifier.getName().startsWith(MODULE_PREFIX)) {
            return super.preloadModule(identifier);
        } else {
            return preloadModule(identifier, mainModuleLoader);
        }
    }

    @SuppressWarnings("unchecked")
    @Override
    public ModuleSpec findModule(ModuleIdentifier identifier) throws ModuleLoadException {
        ServiceController<ModuleDefinition> controller = (ServiceController<ModuleDefinition>) serviceContainer.getService(moduleSpecServiceName(identifier));
        if (controller == null) {
            ServerLogger.MODULE_SERVICE_LOGGER.debugf("Could not load module '%s' as corresponding module spec service '%s' was not found", identifier, identifier);
            return null;
        }
        ModuleSpecLoadListener listener = new ModuleSpecLoadListener(identifier);
        controller.addListener(listener);
        return listener.getModuleSpec();
    }

    @Override
    public String toString() {
        return "Service Module Loader";
    }

    @Override
    public synchronized void start(StartContext context) throws StartException {
        if (serviceContainer != null) {
            throw ServerMessages.MESSAGES.serviceModuleLoaderAlreadyStarted();
        }
        serviceContainer = context.getController().getServiceContainer();
    }

    @Override
    public synchronized void stop(StopContext context) {
        if (serviceContainer == null) {
            throw ServerMessages.MESSAGES.serviceModuleLoaderAlreadyStopped();
        }
        serviceContainer = null;
    }

    @Override
    public ServiceModuleLoader getValue() throws IllegalStateException, IllegalArgumentException {
        return this;
    }

    public void relinkModule(Module module) throws ModuleLoadException {
        relink(module);
    }

    public static void addService(final ServiceTarget serviceTarget, final Bootstrap.Configuration configuration) {
        final Service<ServiceModuleLoader> service = new ServiceModuleLoader(configuration.getModuleLoader());
        final ServiceBuilder<?> serviceBuilder = serviceTarget.addService(Services.JBOSS_SERVICE_MODULE_LOADER, service);
        serviceBuilder.install();
    }

    /**
     * Returns the corresponding ModuleSpec service name for the given module.
     *
     * @param identifier The module identifier
     * @return The service name of the ModuleSpec service
     */
    public static ServiceName moduleSpecServiceName(ModuleIdentifier identifier) {
        if (!isDynamicModule(identifier)) {
            ServerMessages.MESSAGES.missingModulePrefix(identifier, MODULE_PREFIX);
        }
        return MODULE_SPEC_SERVICE_PREFIX.append(identifier.getName()).append(identifier.getSlot());
    }

    public static void installModuleResolvedService(ServiceTarget serviceTarget, ModuleIdentifier identifier) {
        final ValueService<ModuleIdentifier> resolvedService = new ValueService<ModuleIdentifier>(new ImmediateValue<ModuleIdentifier>(identifier));
        serviceTarget.addService(ServiceModuleLoader.moduleResolvedServiceName(identifier), resolvedService)
                .addDependency(moduleSpecServiceName(identifier))
                .install();
    }

    /**
     * Returns the corresponding module resolved service name for the given module.
     *
     * The module resolved service is basically a latch that prevents the module from being loaded
     * until all the transitive dependencies that it depends upon have have their module spec services
     * come up.
     *
     * @param identifier The module identifier
     * @return The service name of the ModuleSpec service
     */
    public static ServiceName moduleResolvedServiceName(ModuleIdentifier identifier) {
        if (!isDynamicModule(identifier)) {
            ServerMessages.MESSAGES.missingModulePrefix(identifier, MODULE_PREFIX);
        }
        return MODULE_RESOLVED_SERVICE_PREFIX.append(identifier.getName()).append(identifier.getSlot());
    }

    /**
     * Returns true if the module identifier is a dynamic module that will be loaded by this module loader
     */
    public static boolean isDynamicModule(ModuleIdentifier identifier) {
        return identifier.getName().startsWith(MODULE_PREFIX);
    }

    /**
     * Returns the corresponding ModuleLoadService service name for the given module.
     *
     * @param identifier The module identifier
     * @return The service name of the ModuleLoadService service
     */
    public static ServiceName moduleServiceName(ModuleIdentifier identifier) {
        if (!identifier.getName().startsWith(MODULE_PREFIX)) {
            ServerMessages.MESSAGES.missingModulePrefix(identifier, MODULE_PREFIX);
        }
        return MODULE_SERVICE_PREFIX.append(identifier.getName()).append(identifier.getSlot());
    }
}
