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/**
 * Copyright (C) 2012 Ness Computing, Inc.
 *
 * 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 com.nesscomputing.jmx.jolokia;

import java.lang.annotation.Annotation;
import java.util.Map;

import javax.servlet.http.HttpServlet;

import org.apache.commons.configuration.Configuration;
import org.jolokia.backend.BackendManager;
import org.jolokia.http.HttpRequestHandler;
import org.jolokia.restrictor.AllowAllRestrictor;
import org.jolokia.restrictor.Restrictor;
import org.jolokia.util.ConfigKey;
import org.jolokia.util.LogHandler;

import com.google.common.collect.Maps;
import com.google.inject.AbstractModule;
import com.google.inject.Inject;
import com.google.inject.Injector;
import com.google.inject.Key;
import com.google.inject.Provider;
import com.google.inject.Provides;
import com.google.inject.Scopes;
import com.google.inject.Singleton;
import com.google.inject.name.Names;
import com.google.inject.servlet.ServletModule;
import com.nesscomputing.config.Config;
import com.nesscomputing.config.ConfigProvider;
import com.nesscomputing.lifecycle.Lifecycle;
import com.nesscomputing.lifecycle.LifecycleListener;
import com.nesscomputing.lifecycle.LifecycleStage;
import com.nesscomputing.logging.Log;

/**
 * Bind the jolokia servlet in the Trumpet context.
 */
public class JolokiaModule extends ServletModule
{
    static final Annotation JOLOKIA_SERVLET = Names.named("_jolokiaServlet");

    @Override
    public void configureServlets()
    {
        bind (JolokiaConfig.class).toProvider(ConfigProvider.of(JolokiaConfig.class));

        bind (HttpServlet.class).annotatedWith(JOLOKIA_SERVLET).toProvider(JolokiaServletProvider.class).in(Scopes.SINGLETON);
        serve("/jolokia/*").with(Key.get(HttpServlet.class, JOLOKIA_SERVLET));
        configureRestrictor();
    }

    /**
     * Override this method to implement access restrictions.
     */
    protected void configureRestrictor()
    {
        bind(Restrictor.class).to(AllowAllRestrictor.class).in(Scopes.SINGLETON);
    }

    static class JolokiaServletProvider implements Provider
    {

        private final JolokiaConfig config;
        private final Injector injector;

        @Inject
        JolokiaServletProvider(JolokiaConfig config, Injector injector)
        {
            this.config = config;
            this.injector = injector;
        }

        @Override
        public HttpServlet get()
        {
            if (config.isJolokiaEnabled())
            {
                return injector.createChildInjector(new RealJolokiaModule()).getInstance(JolokiaServlet.class);
            }

            return new NoJolokiaServlet();
        }
    }

    private static class RealJolokiaModule extends AbstractModule
    {
        @Override
        protected void configure()
        {
            bind (JolokiaServlet.class);
        }

        @Provides
        @Singleton
        BackendManager getBackendManager(final Config config, final LogHandler logHandler, final Restrictor restrictor, final Lifecycle lifecycle)
        {
            final Configuration jolokiaConfig = config.getConfiguration("ness.jolokia");
            final Map configMap = Maps.newEnumMap(ConfigKey.class);

            for (final ConfigKey key : ConfigKey.values()) {
                if (key.isGlobalConfig()) {
                    configMap.put(key, jolokiaConfig.getString(key.getKeyValue(), key.getDefaultValue()));
                }
            }

            final BackendManager backendManager = new BackendManager(configMap, logHandler, restrictor);

            lifecycle.addListener(LifecycleStage.STOP_STAGE, new LifecycleListener() {
                @Override
                public void onStage(LifecycleStage lifecycleStage)
                {
                    backendManager.destroy();
                }
            });

            return backendManager;
        }

        @Provides
        @Singleton
        HttpRequestHandler getHttpRequestHandler(final LogHandler logHandler, final BackendManager backendManager)
        {
            return new HttpRequestHandler(backendManager, logHandler);
        }

        @Provides
        @Singleton
        LogHandler getLogHandler()
        {
            final Log jolokiaLog = Log.forName("jolokia");

            return new LogHandler() {

                @Override
                public void debug(final String message)
                {
                    jolokiaLog.debug(message);
                }

                @Override
                public void info(final String message)
                {
                    jolokiaLog.info(message);
                }

                @Override
                public void error(final String message, final Throwable t)
                {
                    jolokiaLog.error(t, message);
                }
            };
        }
    }
}