/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * 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.oozie.service;

import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.util.ReflectionUtils;
import org.apache.hadoop.util.VersionInfo;
import org.apache.oozie.BuildInfo;
import org.apache.oozie.client.OozieClient.SYSTEM_MODE;
import org.apache.oozie.util.DateUtils;
import org.apache.oozie.util.XLog;
import org.apache.oozie.util.Instrumentable;
import org.apache.oozie.util.Instrumentation;
import org.apache.oozie.util.IOUtils;
import org.apache.oozie.ErrorCode;

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.io.IOException;
import java.io.File;

/**
 * Services is a singleton that manages the lifecycle of all registered {@link Services}. <p/> It has 2 built in
 * services: {@link XLogService} and {@link ConfigurationService}. <p/> The rest of the services are loaded from the
 * {@link #CONF_SERVICE_CLASSES} configuration property. The services class names must be separated by commas (spaces
 * and enters are allowed). <p/> The {@link #CONF_SYSTEM_MODE} configuration property is any of
 * NORMAL/SAFEMODE/NOWEBSERVICE. <p/> Services are loaded and initialized in the order they are defined in the in
 * configuration property. <p/> After all services are initialized, if the Instrumentation service is present, all
 * services that implement the {@link Instrumentable} are instrumented. <p/> Services are destroyed in reverse order.
 * <p/> If services initialization fail, initialized services are immediatly destroyed.
 */
public class Services {
    private static final int MAX_SYSTEM_ID_LEN = 10;

    /**
     * Environment variable that indicates the location of the Oozie home directory.
     * The Oozie home directory is used to pick up the conf/ directory from
     */
    public static final String OOZIE_HOME_DIR = "oozie.home.dir";

    public static final String CONF_SYSTEM_ID = "oozie.system.id";

    public static final String CONF_SERVICE_CLASSES = "oozie.services";

    public static final String CONF_SERVICE_EXT_CLASSES = "oozie.services.ext";

    public static final String CONF_SYSTEM_MODE = "oozie.systemmode";

    public static final String CONF_DELETE_RUNTIME_DIR = "oozie.delete.runtime.dir.on.shutdown";

    private static Services SERVICES;

    private SYSTEM_MODE systemMode;
    private String runtimeDir;
    private Configuration conf;
    private Map<Class<? extends Service>, Service> services = new LinkedHashMap<Class<? extends Service>, Service>();
    private String systemId;
    private static String oozieHome;

    public static void setOozieHome() throws ServiceException {
        oozieHome = System.getProperty(OOZIE_HOME_DIR);
        if (oozieHome == null) {
            throw new ServiceException(ErrorCode.E0000);
        }
        File file = new File(oozieHome);
        if (!file.isAbsolute()) {
            throw new ServiceException(ErrorCode.E0003, oozieHome);
        }
        if (!file.exists()) {
            throw new ServiceException(ErrorCode.E0004, oozieHome);
        }
    }

    public static String getOozieHome() throws ServiceException {
        return oozieHome;
    }

    /**
     * Create a services. <p/> The built in services are initialized.
     *
     * @throws ServiceException thrown if any of the built in services could not initialize.
     */
    public Services() throws ServiceException {
        setOozieHome();
        if (SERVICES != null) {
            XLog log = XLog.getLog(getClass());
            log.warn(XLog.OPS, "Previous services singleton active, destroying it");
            SERVICES.destroy();
            SERVICES = null;
        }
        setServiceInternal(XLogService.class, false);
        setServiceInternal(ConfigurationService.class, true);
        conf = get(ConfigurationService.class).getConf();
        DateUtils.setConf(conf);
        if (!DateUtils.getOozieProcessingTimeZone().equals(DateUtils.UTC)) {
            XLog.getLog(getClass()).warn("Oozie configured to work in a timezone other than UTC: {0}",
                                         DateUtils.getOozieProcessingTimeZone().getID());
        }
        systemId = conf.get(CONF_SYSTEM_ID, ("oozie-" + System.getProperty("user.name")));
        if (systemId.length() > MAX_SYSTEM_ID_LEN) {
            systemId = systemId.substring(0, MAX_SYSTEM_ID_LEN);
            XLog.getLog(getClass()).warn("System ID [{0}] exceeds maximum length [{1}], trimming", systemId,
                                         MAX_SYSTEM_ID_LEN);
        }
        setSystemMode(SYSTEM_MODE.valueOf(conf.get(CONF_SYSTEM_MODE, SYSTEM_MODE.NORMAL.toString())));
        runtimeDir = createRuntimeDir();
    }

    private String createRuntimeDir() throws ServiceException {
        try {
            File file = File.createTempFile(getSystemId(), ".dir");
            file.delete();
            if (!file.mkdir()) {
                ServiceException ex = new ServiceException(ErrorCode.E0001, file.getAbsolutePath());
                XLog.getLog(getClass()).fatal(ex);
                throw ex;
            }
            XLog.getLog(getClass()).info("Initialized runtime directory [{0}]", file.getAbsolutePath());
            return file.getAbsolutePath();
        }
        catch (IOException ex) {
            ServiceException sex = new ServiceException(ErrorCode.E0001, "", ex);
            XLog.getLog(getClass()).fatal(ex);
            throw sex;
        }
    }

    /**
     * Return active system mode. <p/> .
     *
     * @return
     */

    public SYSTEM_MODE getSystemMode() {
        return systemMode;
    }

    /**
     * Return the runtime directory of the Oozie instance. <p/> The directory is created under TMP and it is always a
     * new directory per Services initialization.
     *
     * @return the runtime directory of the Oozie instance.
     */
    public String getRuntimeDir() {
        return runtimeDir;
    }

    /**
     * Return the system ID, the value defined in the {@link #CONF_SYSTEM_ID} configuration property.
     *
     * @return the system ID, the value defined in the {@link #CONF_SYSTEM_ID} configuration property.
     */
    public String getSystemId() {
        return systemId;
    }

    /**
     * Set and set system mode.
     *
     * @param sysMode system mode
     */

    public synchronized void setSystemMode(SYSTEM_MODE sysMode) {
        if (this.systemMode != sysMode) {
            XLog log = XLog.getLog(getClass());
            log.info(XLog.OPS, "Exiting " + this.systemMode + " Entering " + sysMode);
        }
        this.systemMode = sysMode;
    }

    /**
     * Return the services configuration.
     *
     * @return services configuraiton.
     */
    public Configuration getConf() {
        return conf;
    }

    /**
     * Initialize all services define in the {@link #CONF_SERVICE_CLASSES} configuration property.
     *
     * @throws ServiceException thrown if any of the services could not initialize.
     */
    @SuppressWarnings("unchecked")
    public void init() throws ServiceException {
        XLog log = new XLog(LogFactory.getLog(getClass()));
        log.trace("Initializing");
        SERVICES = this;
        try {
            loadServices();
        }
        catch (RuntimeException rex) {
            XLog.getLog(getClass()).fatal(rex.getMessage(), rex);
            throw rex;
        }
        catch (ServiceException ex) {
            XLog.getLog(getClass()).fatal(ex.getMessage(), ex);
            SERVICES = null;
            throw ex;
        }
        InstrumentationService instrService = get(InstrumentationService.class);
        if (instrService != null) {
            Instrumentation instr = instrService.get();
            for (Service service : services.values()) {
                if (service instanceof Instrumentable) {
                    ((Instrumentable) service).instrument(instr);
                }
            }
            instr.addVariable("oozie", "version", new Instrumentation.Variable<String>() {
                @Override
                public String getValue() {
                    return BuildInfo.getBuildInfo().getProperty(BuildInfo.BUILD_VERSION);
                }
            });
            instr.addVariable("oozie", "mode", new Instrumentation.Variable<String>() {
                @Override
                public String getValue() {
                    return getSystemMode().toString();
                }
            });
        }
        log.info("Initialized");
        log.info("Running with JARs for Hadoop version [{0}]", VersionInfo.getVersion());
        log.info("Oozie System ID [{0}] started!", getSystemId());
    }

    /**
     * Loads the specified services.
     *
     * @param classes services classes to load.
     * @param list    list of loaded service in order of appearance in the
     *                configuration.
     * @throws ServiceException thrown if a service class could not be loaded.
     */
    private void loadServices(Class[] classes, List<Service> list) throws ServiceException {
        XLog log = new XLog(LogFactory.getLog(getClass()));
        for (Class klass : classes) {
            try {
                Service service = (Service) klass.newInstance();
                log.debug("Loading service [{0}] implementation [{1}]", service.getInterface(),
                        service.getClass());
                if (!service.getInterface().isInstance(service)) {
                    throw new ServiceException(ErrorCode.E0101, klass, service.getInterface().getName());
                }
                list.add(service);
            } catch (ServiceException ex) {
                throw ex;
            } catch (Exception ex) {
                throw new ServiceException(ErrorCode.E0102, klass, ex.getMessage(), ex);
            }
        }
    }

    /**
     * Loads services defined in <code>services</code> and
     * <code>services.ext</code> and de-dups them.
     *
     * @return List of final services to initialize.
     * @throws ServiceException throw if the services could not be loaded.
     */
    private void loadServices() throws ServiceException {
        XLog log = new XLog(LogFactory.getLog(getClass()));
        try {
            Map<Class, Service> map = new LinkedHashMap<Class, Service>();
            Class[] classes = conf.getClasses(CONF_SERVICE_CLASSES);
            log.debug("Services list obtained from property '" + CONF_SERVICE_CLASSES + "'");
            Class[] classesExt = conf.getClasses(CONF_SERVICE_EXT_CLASSES);
            log.debug("Services list obtained from property '" + CONF_SERVICE_EXT_CLASSES + "'");
            List<Service> list = new ArrayList<Service>();
            loadServices(classes, list);
            loadServices(classesExt, list);

            //removing duplicate services, strategy: last one wins
            for (Service service : list) {
                if (map.containsKey(service.getInterface())) {
                    log.debug("Replacing service [{0}] implementation [{1}]", service.getInterface(),
                            service.getClass());
                }
                map.put(service.getInterface(), service);
            }
            for (Map.Entry<Class, Service> entry : map.entrySet()) {
                setService(entry.getValue().getClass());
            }
        } catch (RuntimeException rex) {
            log.fatal("Runtime Exception during Services Load. Check your list of '" + CONF_SERVICE_CLASSES + "' or '" + CONF_SERVICE_EXT_CLASSES + "'");
            throw new ServiceException(ErrorCode.E0103, rex.getMessage(), rex);
        }
    }

    /**
     * Destroy all services.
     */
    public void destroy() {
        XLog log = new XLog(LogFactory.getLog(getClass()));
        log.trace("Shutting down");
        boolean deleteRuntimeDir = false;
        if (conf != null) {
            deleteRuntimeDir = conf.getBoolean(CONF_DELETE_RUNTIME_DIR, false);
        }
        if (services != null) {
            List<Service> list = new ArrayList<Service>(services.values());
            Collections.reverse(list);
            for (Service service : list) {
                try {
                    log.trace("Destroying service[{0}]", service.getInterface());
                    if (service.getInterface() == XLogService.class) {
                        log.info("Shutdown");
                    }
                    service.destroy();
                }
                catch (Throwable ex) {
                    log.error("Error destroying service[{0}], {1}", service.getInterface(), ex.getMessage(), ex);
                }
            }
        }
        if (deleteRuntimeDir) {
            try {
                IOUtils.delete(new File(runtimeDir));
            }
            catch (IOException ex) {
                log.error("Error deleting runtime directory [{0}], {1}", runtimeDir, ex.getMessage(), ex);
            }
        }
        services = null;
        conf = null;
        SERVICES = null;
    }

    /**
     * Return a service by its public interface.
     *
     * @param serviceKlass service public interface.
     * @return the associated service, or <code>null</code> if not define.
     */
    @SuppressWarnings("unchecked")
    public <T extends Service> T get(Class<T> serviceKlass) {
        return (T) services.get(serviceKlass);
    }

    /**
     * Set a service programmatically. <p/> The service will be initialized by the services. <p/> If a service is
     * already defined with the same public interface it will be destroyed.
     *
     * @param klass service klass
     * @throws ServiceException if the service could not be initialized, at this point all services have been
     * destroyed.
     */
    public void setService(Class<? extends Service> klass) throws ServiceException {
        setServiceInternal(klass, true);
    }

    private void setServiceInternal(Class<? extends Service> klass, boolean logging) throws ServiceException {
        try {
            Service newService = (Service) ReflectionUtils.newInstance(klass, null);
            Service oldService = services.get(newService.getInterface());
            if (oldService != null) {
                oldService.destroy();
            }
            if (logging) {
                XLog log = new XLog(LogFactory.getLog(getClass()));
                log.trace("Initializing service[{0}] class[{1}]", newService.getInterface(), newService.getClass());
            }
            newService.init(this);
            services.put(newService.getInterface(), newService);
        }
        catch (ServiceException ex) {
            XLog.getLog(getClass()).fatal(ex.getMessage(), ex);
            destroy();
            throw ex;
        }
    }

    /**
     * Return the services singleton.
     *
     * @return services singleton, <code>null</code> if not initialized.
     */
    public static Services get() {
        return SERVICES;
    }

}