/*
    * #%L
    * wcm.io
    * %%
    * Copyright (C) 2015 wcm.io
    * %%
    * 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.
   * #L%
   */
  package io.wcm.caravan.hal.docs.impl;
  
  import io.wcm.caravan.jaxrs.publisher.ApplicationPath;
  
  import java.util.Dictionary;
  import java.util.Hashtable;
  
  import org.apache.felix.scr.annotations.Activate;
  import org.apache.felix.scr.annotations.Component;
  import org.apache.felix.scr.annotations.Deactivate;
  import org.apache.felix.scr.annotations.Reference;
  import org.osgi.framework.Bundle;
  import org.osgi.framework.BundleContext;
  import org.osgi.framework.BundleEvent;
  import org.osgi.service.component.ComponentConstants;
  import org.osgi.service.component.ComponentContext;
  import org.osgi.service.component.ComponentFactory;
  import org.osgi.service.component.ComponentInstance;
  import org.osgi.service.http.HttpService;
  import org.osgi.service.http.NamespaceException;
  import org.osgi.util.tracker.BundleTracker;
  import org.osgi.util.tracker.BundleTrackerCustomizer;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Tracks bundles that contain HAL documentation files generated by hal-docs-maven-plugin, and mounts them
   * via HTTP service to /docs/api/{serviceId}/*.
   */
  @Component(immediate = true)
  public class HalDocsBundleTracker implements BundleTrackerCustomizer<ComponentInstance> {
  
    static final String DOCS_RESOURCES_URI_PREFIX = "/docs/resources";
    static final String CLASSPATH_FRONTEND = "HALDOCS-TEMPLATE-INF/frontend";
  
    private static final Logger log = LoggerFactory.getLogger(HalDocsBundleTracker.class);
  
    private BundleContext bundleContext;
    private BundleTracker bundleTracker;
  
    @Reference(target = "(" + ComponentConstants.COMPONENT_FACTORY + "=" + HalDocsServlet.FACTORY + ")")
    private ComponentFactory servletFactory;
  
    @Reference
    private HttpService httpService;
  
    @Activate
    void activate(ComponentContext componentContext) throws NamespaceException {
      bundleContext = componentContext.getBundleContext();
      this.bundleTracker = new BundleTracker<ComponentInstance>(bundleContext, Bundle.ACTIVE, this);
      this.bundleTracker.open();
  
      // mount static resources for docs frontend
      httpService.registerResources(DOCS_RESOURCES_URI_PREFIX, CLASSPATH_FRONTEND, null);
    }
  
    @Deactivate
    void deactivate(ComponentContext componentContext) {
      this.bundleTracker.close();
      httpService.unregister(DOCS_RESOURCES_URI_PREFIX);
    }
  
    @Override
    public ComponentInstance addingBundle(Bundle bundle, BundleEvent event) {
      String docsPath = DocsPath.get(bundle);
      if (docsPath != null) {
  
        if (log.isInfoEnabled()) {
          log.info("Mount HAL docs for {} to {}", bundle.getSymbolicName(), docsPath);
        }
  
        // register HAL docs servlet on HTTP whiteboard
        Dictionary<String, Object> serviceConfig = new Hashtable<>();
        serviceConfig.put("alias", docsPath);
        serviceConfig.put(HalDocsServlet.PROPERTY_BUNDLE, bundle);
        return servletFactory.newInstance(serviceConfig);
      }
      return null;
    }
  
   @Override
   public void modifiedBundle(Bundle bundle, BundleEvent event, ComponentInstance componentInstance) {
     // nothing to do
   }
 
   @Override
   public void removedBundle(Bundle bundle, BundleEvent event, ComponentInstance componentInstance) {
     if (componentInstance == null) {
       return;
     }
     if (log.isInfoEnabled()) {
       String applicationPath = ApplicationPath.get(bundle);
       String docsPath = DocsPath.get(applicationPath);
       log.info("Unmount HAL docs for {} from {}", bundle.getSymbolicName(), docsPath);
     }
     componentInstance.dispose();
   }
 
 }