package com.atlassian.plugin.osgi.external;
   
   import com.atlassian.plugin.ModuleDescriptor;
   import com.atlassian.plugin.PluginParseException;
   import com.atlassian.plugin.hostcontainer.HostContainer;
   import com.atlassian.plugin.hostcontainer.DefaultHostContainer;
   
   import java.util.Collections;
   import java.util.Set;
  
  /**
   * A single module descriptor factory for plugins to use when they want to expose just one plugin.  Uses
   * {@link HostContainer} to optionally provide autowiring for new descriptor instances.
   *
   * @since 2.1
   */
  public class SingleModuleDescriptorFactory<T extends ModuleDescriptor<?>> implements ListableModuleDescriptorFactory
  {
      private final String type;
      private final Class<T> moduleDescriptorClass;
      private final HostContainer hostContainer;
  
      /**
       * Constructs an instance using a specific host container
       * @param hostContainer The host container to use to create descriptor instances
       * @param type The type of module
       * @param moduleDescriptorClass The descriptor class
       * @since 2.2.0
       */
      public SingleModuleDescriptorFactory(final HostContainer hostContainer, final String type, final Class<T> moduleDescriptorClass)
      {
          this.moduleDescriptorClass = moduleDescriptorClass;
          this.type = type;
          this.hostContainer = hostContainer;
      }
  
      public ModuleDescriptor getModuleDescriptor(final String type) throws PluginParseException, IllegalAccessException, InstantiationException, ClassNotFoundException
      {
          T result = null;
          if (this.type.equals(type))
          {
              // We can't use an autowired bean factory to create the instance because it would be loaded by this class's
              // classloader, which will not have access to the spring instance in bundle space.
              result = hostContainer.create(moduleDescriptorClass);
          }
          return result;
      }
  
      public boolean hasModuleDescriptor(final String type)
      {
          return (this.type.equals(type));
      }
  
      @SuppressWarnings("unchecked")
      public Class<? extends ModuleDescriptor<?>> getModuleDescriptorClass(final String type)
      {
          return (this.type.equals(type) ? moduleDescriptorClass : null);
      }
  
      @SuppressWarnings("unchecked")
      public Set<Class<ModuleDescriptor<?>>> getModuleDescriptorClasses()
      {
          return Collections.singleton((Class<ModuleDescriptor<?>>) moduleDescriptorClass);
      }
  
      public HostContainer getHostContainer()
      {
          return hostContainer;
      }
  }