/*
 * Copyright (c) 2016 Brocade Communications Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.controller.blueprint;

import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import java.lang.management.ManagementFactory;
import java.util.AbstractMap.SimpleEntry;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Deque;
import java.util.Dictionary;
import java.util.Hashtable;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map.Entry;
import java.util.Set;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import javax.annotation.Nullable;
import javax.management.InstanceNotFoundException;
import javax.management.ObjectName;
import javax.xml.parsers.ParserConfigurationException;
import org.apache.aries.blueprint.services.BlueprintExtenderService;
import org.apache.aries.quiesce.participant.QuiesceParticipant;
import org.apache.aries.util.AriesFrameworkUtil;
import org.opendaylight.controller.config.api.ConfigRegistry;
import org.opendaylight.controller.config.api.ConflictingVersionException;
import org.opendaylight.controller.config.api.ModuleIdentifier;
import org.opendaylight.controller.config.api.ValidationException;
import org.opendaylight.controller.config.facade.xml.ConfigExecution;
import org.opendaylight.controller.config.facade.xml.ConfigSubsystemFacade;
import org.opendaylight.controller.config.facade.xml.ConfigSubsystemFacadeFactory;
import org.opendaylight.controller.config.facade.xml.TestOption;
import org.opendaylight.controller.config.facade.xml.mapping.config.Config;
import org.opendaylight.controller.config.facade.xml.strategy.EditStrategyType;
import org.opendaylight.controller.config.util.ConfigRegistryJMXClient;
import org.opendaylight.controller.config.util.xml.DocumentedException;
import org.opendaylight.controller.config.util.xml.XmlElement;
import org.opendaylight.controller.config.util.xml.XmlMappingConstants;
import org.opendaylight.controller.config.util.xml.XmlUtil;
import org.osgi.framework.Bundle;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceReference;
import org.osgi.framework.ServiceRegistration;
import org.osgi.service.blueprint.container.EventConstants;
import org.osgi.service.event.EventHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;

/**
 * Implementation of the BlueprintContainerRestartService.
 *
 * @author Thomas Pantelis
 */
class BlueprintContainerRestartServiceImpl implements AutoCloseable, BlueprintContainerRestartService {
    private static final Logger LOG = LoggerFactory.getLogger(BlueprintContainerRestartServiceImpl.class);
    private static final int CONTAINER_CREATE_TIMEOUT_IN_MINUTES = 5;
    private static final String CONFIG_MODULE_NAMESPACE_PROP = "config-module-namespace";
    private static final String CONFIG_MODULE_NAME_PROP = "config-module-name";
    private static final String CONFIG_INSTANCE_NAME_PROP = "config-instance-name";

    private final ExecutorService restartExecutor = Executors.newSingleThreadExecutor(new ThreadFactoryBuilder()
            .setDaemon(true).setNameFormat("BlueprintContainerRestartService").build());

    private BlueprintExtenderService blueprintExtenderService;
    private QuiesceParticipant quiesceParticipant;

    void setBlueprintExtenderService(final BlueprintExtenderService blueprintExtenderService) {
        this.blueprintExtenderService = blueprintExtenderService;
    }

    void setQuiesceParticipant(final QuiesceParticipant quiesceParticipant) {
        this.quiesceParticipant = quiesceParticipant;
    }

    public void restartContainer(final Bundle bundle, final List<Object> paths) {
        if (restartExecutor.isShutdown()) {
            return;
        }

        LOG.debug("restartContainer for bundle {}", bundle);

        restartExecutor.execute(() -> {
            blueprintExtenderService.destroyContainer(bundle, blueprintExtenderService.getContainer(bundle));
            blueprintExtenderService.createContainer(bundle, paths);
        });
    }

    @Override
    public void restartContainerAndDependents(final Bundle bundle) {
        if (restartExecutor.isShutdown()) {
            return;
        }

        LOG.debug("restartContainerAndDependents for bundle {}", bundle);

        restartExecutor.execute(() -> restartContainerAndDependentsInternal(bundle));
    }

    private void restartContainerAndDependentsInternal(Bundle forBundle) {
        Preconditions.checkNotNull(blueprintExtenderService);
        Preconditions.checkNotNull(quiesceParticipant);

        // We use a LinkedHashSet to preserve insertion order as we walk the service usage hierarchy.
        Set<Bundle> containerBundlesSet = new LinkedHashSet<>();
        List<Entry<String, ModuleIdentifier>> configModules = new ArrayList<>();
        findDependentContainersRecursively(forBundle, containerBundlesSet, configModules);

        List<Bundle> containerBundles = new ArrayList<>(containerBundlesSet);

        LOG.info("Restarting blueprint containers for bundle {} and its dependent bundles {}", forBundle,
                containerBundles.subList(1, containerBundles.size()));

        // The blueprint containers are created asynchronously so we register a handler for blueprint events
        // that are sent when a container is complete, successful or not. The CountDownLatch tells when all
        // containers are complete. This is done to ensure all blueprint containers are finished before we
        // restart config modules.
        final CountDownLatch containerCreationComplete = new CountDownLatch(containerBundles.size());
        ServiceRegistration<?> eventHandlerReg = registerEventHandler(forBundle.getBundleContext(), event -> {
            LOG.debug("handleEvent {} for bundle {}", event.getTopic(), event.getProperty(EventConstants.BUNDLE));
            if (containerBundles.contains(event.getProperty(EventConstants.BUNDLE))) {
                containerCreationComplete.countDown();
            }
        });

        final Runnable createContainerCallback = () -> createContainers(containerBundles);

        // Destroy the container down-top recursively and once done, restart the container top-down
        destroyContainers(new ArrayDeque<>(Lists.reverse(containerBundles)), createContainerCallback);


        try {
            if (!containerCreationComplete.await(CONTAINER_CREATE_TIMEOUT_IN_MINUTES, TimeUnit.MINUTES)) {
                LOG.warn("Failed to restart all blueprint containers within {} minutes. Attempted to restart {} {} "
                        + "but only {} completed restart", CONTAINER_CREATE_TIMEOUT_IN_MINUTES, containerBundles.size(),
                        containerBundles, containerBundles.size() - containerCreationComplete.getCount());
                return;
            }
        } catch (InterruptedException e) {
            LOG.debug("CountDownLatch await was interrupted - returning");
            return;
        }

        AriesFrameworkUtil.safeUnregisterService(eventHandlerReg);

        // Now restart any associated config system Modules.
        restartConfigModules(forBundle.getBundleContext(), configModules);
    }

    /**
     * Recursively quiesce and destroy the bundles one by one in order to maintain synchronicity and ordering.
     * @param remainingBundlesToDestroy the list of remaining bundles to destroy.
     * @param createContainerCallback a {@link Runnable} to {@code run()} when the recursive function is completed.
     */
    private void destroyContainers(final Deque<Bundle> remainingBundlesToDestroy,
            final Runnable createContainerCallback) {

        final Bundle nextBundle;
        synchronized (remainingBundlesToDestroy) {
            if (remainingBundlesToDestroy.isEmpty()) {
                LOG.debug("All blueprint containers were quiesced and destroyed");
                createContainerCallback.run();
                return;
            }

            nextBundle = remainingBundlesToDestroy.poll();
        }

        // The Quiesce capability is a like a soft-stop, clean-stop. In the case of the Blueprint extender, in flight
        // service calls are allowed to finish; they're counted in and counted out, and no new calls are allowed. When
        // there are no in flight service calls, the bundle is told to stop. The Blueprint bundle itself doesn't know
        // this is happening which is a key design point. In the case of Blueprint, the extender ensures no new Entity
        // Managers(EMs) are created. Then when all those EMs are closed the quiesce operation reports that it is
        // finished.
        // To properly restart the blueprint containers, first we have to quiesce the list of bundles, and once done, it
        // is safe to destroy their BlueprintContainer, so no reference is retained.
        //
        // Mail - thread explaining Quiesce API:
        //      https://www.mail-archive.com/dev@aries.apache.org/msg08403.html

        // Quiesced the bundle to unregister the associated BlueprintContainer
        quiesceParticipant.quiesce(bundlesQuiesced -> {

            // Destroy the container once Quiesced
            Arrays.stream(bundlesQuiesced).forEach(quiescedBundle -> {
                LOG.debug("Quiesced bundle {}", quiescedBundle);
                blueprintExtenderService.destroyContainer(
                        quiescedBundle, blueprintExtenderService.getContainer(quiescedBundle));
            });

            destroyContainers(remainingBundlesToDestroy, createContainerCallback);

        }, Collections.singletonList(nextBundle));
    }

    private void createContainers(List<Bundle> containerBundles) {
        containerBundles.forEach(bundle -> {
            List<Object> paths = BlueprintBundleTracker.findBlueprintPaths(bundle);

            LOG.info("Restarting blueprint container for bundle {} with paths {}", bundle, paths);

            blueprintExtenderService.createContainer(bundle, paths);
        });
    }

    private void restartConfigModules(BundleContext bundleContext, List<Entry<String,
            ModuleIdentifier>> configModules) {
        if (configModules.isEmpty()) {
            return;
        }

        ServiceReference<ConfigSubsystemFacadeFactory> configFacadeFactoryRef = bundleContext
                .getServiceReference(ConfigSubsystemFacadeFactory.class);
        if (configFacadeFactoryRef == null) {
            LOG.debug("ConfigSubsystemFacadeFactory service reference not found");
            return;
        }

        ConfigSubsystemFacadeFactory configFacadeFactory = bundleContext.getService(configFacadeFactoryRef);
        if (configFacadeFactory == null) {
            LOG.debug("ConfigSubsystemFacadeFactory service not found");
            return;
        }

        try (ConfigSubsystemFacade configFacade = configFacadeFactory.createFacade(
                "BlueprintContainerRestartService")) {
            restartConfigModules(configModules, configFacade);
        } catch (ParserConfigurationException | DocumentedException | ValidationException
                | ConflictingVersionException e) {
            LOG.error("Error restarting config modules", e);
        } finally {
            bundleContext.ungetService(configFacadeFactoryRef);
        }

    }

    private void restartConfigModules(List<Entry<String, ModuleIdentifier>> configModules,
            ConfigSubsystemFacade configFacade) throws ParserConfigurationException, DocumentedException,
                    ValidationException, ConflictingVersionException {

        Document document = XmlUtil.newDocument();
        Element dataElement = XmlUtil.createElement(document, XmlMappingConstants.DATA_KEY, Optional.<String>absent());
        Element modulesElement = XmlUtil.createElement(document, XmlMappingConstants.MODULES_KEY,
                Optional.of(XmlMappingConstants.URN_OPENDAYLIGHT_PARAMS_XML_NS_YANG_CONTROLLER_CONFIG));
        dataElement.appendChild(modulesElement);

        Config configMapping = configFacade.getConfigMapping();

        ConfigRegistry configRegistryClient = new ConfigRegistryJMXClient(ManagementFactory.getPlatformMBeanServer());
        for (Entry<String, ModuleIdentifier> entry : configModules) {
            String moduleNamespace = entry.getKey();
            ModuleIdentifier moduleId = entry.getValue();
            try {
                ObjectName instanceON = configRegistryClient.lookupConfigBean(moduleId.getFactoryName(),
                        moduleId.getInstanceName());

                LOG.debug("Found config module instance ObjectName: {}", instanceON);

                Element moduleElement = configMapping.moduleToXml(moduleNamespace, moduleId.getFactoryName(),
                        moduleId.getInstanceName(), instanceON, document);
                modulesElement.appendChild(moduleElement);
            } catch (InstanceNotFoundException e) {
                LOG.warn("Error looking up config module: namespace {}, module name {}, instance {}",
                        moduleNamespace, moduleId.getFactoryName(), moduleId.getInstanceName(), e);
            }
        }

        if (LOG.isDebugEnabled()) {
            LOG.debug("Pushing config xml: {}", XmlUtil.toString(dataElement));
        }

        ConfigExecution execution = new ConfigExecution(configMapping, XmlElement.fromDomElement(dataElement),
                TestOption.testThenSet, EditStrategyType.recreate);
        configFacade.executeConfigExecution(execution);
        configFacade.commitSilentTransaction();
    }

    /**
     * Recursively finds the services registered by the given bundle and the bundles using those services.
     * User bundles that have an associated blueprint container are added to containerBundles. In addition,
     * if a registered service has an associated config system Module, as determined via the presence of
     * certain service properties, the ModuleIdentifier is added to the configModules list.
     *
     * @param bundle the bundle to traverse
     * @param containerBundles the current set of bundles containing blueprint containers
     * @param configModules the current set of bundles containing config modules
     */
    private void findDependentContainersRecursively(Bundle bundle, Set<Bundle> containerBundles,
            List<Entry<String, ModuleIdentifier>> configModules) {
        if (!containerBundles.add(bundle)) {
            // Already seen this bundle...
            return;
        }

        ServiceReference<?>[] references = bundle.getRegisteredServices();
        if (references != null) {
            for (ServiceReference<?> reference : references) {
                possiblyAddConfigModuleIdentifier(reference, configModules);

                Bundle[] usingBundles = reference.getUsingBundles();
                if (usingBundles != null) {
                    for (Bundle usingBundle : usingBundles) {
                        if (blueprintExtenderService.getContainer(usingBundle) != null) {
                            findDependentContainersRecursively(usingBundle, containerBundles, configModules);
                        }
                    }
                }
            }
        }
    }

    private void possiblyAddConfigModuleIdentifier(ServiceReference<?> reference,
            List<Entry<String, ModuleIdentifier>> configModules) {
        Object moduleNamespace = reference.getProperty(CONFIG_MODULE_NAMESPACE_PROP);
        if (moduleNamespace == null) {
            return;
        }

        String moduleName = getRequiredConfigModuleProperty(CONFIG_MODULE_NAME_PROP, moduleNamespace,
                reference);
        String instanceName = getRequiredConfigModuleProperty(CONFIG_INSTANCE_NAME_PROP, moduleNamespace,
                reference);
        if (moduleName == null || instanceName == null) {
            return;
        }

        LOG.debug("Found service with config module: namespace {}, module name {}, instance {}",
                moduleNamespace, moduleName, instanceName);

        configModules.add(new SimpleEntry<>(moduleNamespace.toString(),
                new ModuleIdentifier(moduleName, instanceName)));
    }

    @Nullable
    private String getRequiredConfigModuleProperty(String propName, Object moduleNamespace,
            ServiceReference<?> reference) {
        Object value = reference.getProperty(propName);
        if (value == null) {
            LOG.warn(
                "OSGi service with {} property is missing property {} therefore the config module can't be restarted",
                CONFIG_MODULE_NAMESPACE_PROP, propName);
            return null;
        }

        return value.toString();
    }

    private ServiceRegistration<?> registerEventHandler(BundleContext bundleContext, EventHandler handler) {
        Dictionary<String, Object> props = new Hashtable<>();
        props.put(org.osgi.service.event.EventConstants.EVENT_TOPIC,
                new String[]{EventConstants.TOPIC_CREATED, EventConstants.TOPIC_FAILURE});
        return bundleContext.registerService(EventHandler.class.getName(), handler, props);
    }

    @Override
    public void close() {
        restartExecutor.shutdownNow();
    }
}