package com.atlassian.plugins.rest.module;
   
   import com.atlassian.plugin.ModuleDescriptor;
   import com.atlassian.plugin.Plugin;
   import com.atlassian.plugin.PluginManager;
   import com.atlassian.plugin.PluginParseException;
   import com.atlassian.plugin.descriptors.AbstractModuleDescriptor;
   import com.atlassian.plugin.module.ModuleFactory;
   import com.atlassian.plugin.osgi.factory.OsgiPlugin;
  import com.atlassian.plugin.servlet.filter.FilterLocation;
  import com.atlassian.plugins.rest.module.servlet.RestServletModuleManager;
  import com.google.common.base.Preconditions;
  import org.dom4j.Element;
  import org.osgi.framework.ServiceRegistration;
  
  import java.util.Collection;
  import java.util.HashSet;
  import java.util.Set;
  
  /**
   * <p>The REST module descriptor.</p>
   * <p>Example configuration in your {@link PluginManager#PLUGIN_DESCRIPTOR_FILENAME plugin descriptor}:</p>
   * &lt;rest key="module-key"&gt;<br/>
   * &nbsp;&nbsp;&nbsp;&nbsp;&lt;url-pattern&gt;/myapi/*&lt;/url-pattern&gt;<br/>
   * &lt;/rest&gt;<br/>
   * <p>Your REST apis will then be available at <code>/context/rest/myapi</code></p>
   */
  public class RestModuleDescriptor extends AbstractModuleDescriptor<Object> {
      private final RestServletModuleManager servletModuleManager;
      /**
       * This is the context path of REST APIs.
       * <p>
       * Typically if the application lives at {@code http://localhost:9090/app} and the REST context path is {@code /rest}, then APIs will be available at {@code http://localhost:9090/app/rest}
       */
      private final String restContext;
  
      private RestApiContext restApiContext;
  
      private ServiceRegistration serviceRegistration;
      private RestServletFilterModuleDescriptor restServletFilterModuleDescriptor;
      private OsgiPlugin osgiPlugin;
      private Element element;
  
      public RestModuleDescriptor(ModuleFactory moduleFactory, RestServletModuleManager servletModuleManager, String restContext) {
          super(moduleFactory);
          this.servletModuleManager = Preconditions.checkNotNull(servletModuleManager);
          this.restContext = Preconditions.checkNotNull(restContext);
      }
  
      @Override
      public void init(Plugin plugin, Element element) throws PluginParseException {
          super.init(plugin, element);
  
          this.restApiContext = new RestApiContext(restContext, parsePath(element), parseVersion(element), parsePackages(element));
  
          osgiPlugin = (OsgiPlugin) plugin;
  
          this.element = element;
      }
  
      public RestApiContext getRestApiContext() {
          return restApiContext;
      }
  
      private String parsePath(Element element) {
          return element.attributeValue("path");
      }
  
      private Set<String> parsePackages(Element rootElement) {
          Set<String> packages = new HashSet<String>();
          for (Element pkgElement : (Collection<Element>) rootElement.elements("package")) {
              packages.add(pkgElement.getTextTrim());
          }
          return packages;
      }
  
      private ApiVersion parseVersion(Element element) {
          try {
              return new ApiVersion(element.attributeValue("version"));
          } catch (InvalidVersionException e) {
              // rethrowing the exception with more information
              throw new InvalidVersionException(plugin, this, e);
          }
      }
  
      private Element updateElementForFilterConfiguration(final Element element) {
          final Element copy = element.createCopy();
  
          // adding the default location
          copy.addAttribute("location", FilterLocation.BEFORE_DISPATCH.name());
  
          // adding the url-pattern
          copy.addElement("url-pattern").addText(restApiContext.getContextlessPathToVersion() + RestApiContext.ANY_PATH_PATTERN);
  
          copy.addAttribute("key", copy.attributeValue("key") + "-filter");
          return copy;
      }
  
      /**
      * @return <code>null</code>, the REST module descriptor doesn't instansiate any module.
      */
     public Object getModule() {
         return null;
     }
 
     @Override
     public boolean equals(Object o) {
         if (o == null) {
             return false;
         }
         if (this == o) {
             return true;
         }
         if (this.getClass() != o.getClass()) {
             return false;
         }
 
         final RestModuleDescriptor that = (RestModuleDescriptor) o;
         return that.getCompleteKey().equals(getCompleteKey());
     }
 
     @Override
     public int hashCode() {
         return getCompleteKey().hashCode();
     }
 
     @Override
     public String toString() {
         return super.toString() +
                 '/' + restContext +
                 (restApiContext != null
                         ? '/' + restApiContext.getApiPath() + '/' + restApiContext.getVersion()
                         : "");
     }
 
     @Override
     public void disabled() {
         if (restServletFilterModuleDescriptor != null) {
             restServletFilterModuleDescriptor.disabled();
             restServletFilterModuleDescriptor = null;
         }
 
         restApiContext.disabled();
 
         if (serviceRegistration != null) {
             try {
                 serviceRegistration.unregister();
             } catch (IllegalStateException ex) {
                 // this has
             }
             serviceRegistration = null;
         }
 
         super.disabled();
     }
 
     @Override
     public void enabled() {
         super.enabled();
         restServletFilterModuleDescriptor = new RestServletFilterModuleDescriptor(osgiPlugin, moduleFactory, servletModuleManager, restApiContext);
         restServletFilterModuleDescriptor.init(plugin, updateElementForFilterConfiguration(element));
         restServletFilterModuleDescriptor.enabled();
 
         // dynamically register the servlet filter that serves the REST API requests
         serviceRegistration = osgiPlugin.getBundle().getBundleContext().registerService(
                 new String[]{
                         restServletFilterModuleDescriptor.getClass().getName(),
                         ModuleDescriptor.class.getName(),
                 }, restServletFilterModuleDescriptor, null);
     }
 }