/*
    * #%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 org.apache.commons.lang3.StringUtils;
  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.ComponentContext;
  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 JSON schema files generated by hal-docs-maven-plugin, and mounts them
   * via HTTP service to /docs/json-schema/{serviceId}/*.
   */
  @Component(immediate = true)
  public class JsonSchemaBundleTracker implements BundleTrackerCustomizer<String> {
  
    /**
     * Header name that contains the documentation path for the json schema files.
     */
    public static final String HEADER_DOMAIN_PATH = "Caravan-HalDocs-DomainPath";
  
    /**
     * prefix for json schema document URLs.
     */
    public static final String SCHEMA_URI_PREFIX = "/docs/json-schema";
  
    /**
     * Classpath prefix where JSON schema files are located.
     */
    public static final String SCHEMA_CLASSPATH_PREFIX = "JSON-SCHEMA-INF";
  
    private static final Logger log = LoggerFactory.getLogger(JsonSchemaBundleTracker.class);
  
    private BundleContext bundleContext;
    private BundleTracker bundleTracker;
  
    @Reference
    private HttpService httpService;
  
    @Activate
    void activate(ComponentContext componentContext) {
      bundleContext = componentContext.getBundleContext();
      this.bundleTracker = new BundleTracker<String>(bundleContext, Bundle.ACTIVE, this);
      this.bundleTracker.open();
    }
  
    @Deactivate
    void deactivate(ComponentContext componentContext) {
      this.bundleTracker.close();
    }
  
    @Override
    public String addingBundle(Bundle bundle, BundleEvent event) {
      String domainPath = getHalDocsDomainPath(bundle);
      if (StringUtils.isNotBlank(domainPath)) {
        String schemaPath = getDocsPath(domainPath);
  
        if (log.isInfoEnabled()) {
          log.info("Mount JSON schema files for {} to {}", bundle.getSymbolicName(), schemaPath);
        }
  
        try {
          httpService.registerResources(schemaPath, SCHEMA_CLASSPATH_PREFIX,
              new HttpContextWrapper(httpService.createDefaultHttpContext(), bundle));
        }
        catch (NamespaceException ex) {
          throw new RuntimeException("Unable to mount JSON schema files to " + schemaPath, ex);
        }
        return schemaPath;
      }
      return null;
   }
 
   @Override
   public void modifiedBundle(Bundle bundle, BundleEvent event, String schemaPath) {
     // nothing to do
   }
 
   @Override
   public void removedBundle(Bundle bundle, BundleEvent event, String schemaPath) {
     if (schemaPath == null) {
       return;
     }
     if (log.isInfoEnabled()) {
       log.info("Unmount JSON schema files for {} from {}", bundle.getSymbolicName(), schemaPath);
     }
     httpService.unregister(schemaPath);
   }
 
   private String getHalDocsDomainPath(Bundle bundle) {
     return bundle.getHeaders().get(HEADER_DOMAIN_PATH);
   }
 
   private String getDocsPath(String domainPath) {
     return SCHEMA_URI_PREFIX + domainPath;
   }
 
 }