/**

  * - Digitalis Internal Framework v2.0 - (C) 2007, Digitalis Informatica. Distribuicao e Gestao de Informatica, Lda.

  * Estrada de Paco de Arcos num.9 - Piso -1 2780-666 Paco de Arcos Telefone: (351) 21 4408990 Fax: (351) 21 4408999

  * http://www.digitalis.pt

  */

 package pt.digitalis.dif.controller;

 import pt.digitalis.dif.controller.interfaces.IChAL;

 import pt.digitalis.dif.controller.interfaces.IDIFDispatcher;

 import pt.digitalis.dif.controller.interfaces.IDIFRequest;

 import pt.digitalis.dif.controller.interfaces.IDIFResponse;

 import pt.digitalis.dif.controller.interfaces.IDispatcherErrorHandler;

 import pt.digitalis.dif.controller.objects.ClientDescriptor;

 import pt.digitalis.dif.controller.objects.RESTAction;

 import pt.digitalis.dif.dem.annotations.controller.Channel;

 import pt.digitalis.dif.dem.managers.IMessageManager;

 import pt.digitalis.dif.exception.controller.BusinessFlowException;

 import pt.digitalis.dif.exception.controller.ControllerException;

 import pt.digitalis.dif.ioc.DIFIoCRegistry;

 import com.newrelic.api.agent.Trace;

 /**

  * Base implementation for all ChALs The API exposed to the Listener entities is the <code>serve()</code> method. All

  * the communication between AbstractChAL and Listener is done through this API.

  * 

  * @param <RequestType>

  *            type original request type

  * @param <ResponseType>

  *            the original response type

  * @author Rodrigo Gonçalves <a href="mailto:rgoncalves@digitalis.pt">rgoncalves@digitalis.pt</a>

  * @author Pedro Viegas <a href="mailto:pviegas@digitalis.pt">pviegas@digitalis.pt</a>

  * @created 2007/03/27

  */

 abstract public class AbstractChAL<RequestType, ResponseType> implements IChAL<RequestType, ResponseType> {

     /** The channel ID */

     private String channelID = null;

     /** The message manager. */

     protected IMessageManager messageManager = DIFIoCRegistry.getRegistry().getImplementation(IMessageManager.class);

     /**

      * Get the id of the channel associated to the ChAL. If the id is unset the method reads the channel id from the

      * annotation.

      * 

      * @return the channel ID read from the {@link Channel} annotation

      */

     public String getChannelID()

     {

         if (channelID == null)

             channelID = this.getClass().getAnnotation(Channel.class).value();

         return channelID;

     }

     /**

      * Creates a client descriptor object identifying the client agent who issued the request

      * 

      * @param originalRequest

      *            the original request object

      * @return the client descriptor for the current request

      * @throws ControllerException

      *             when any runtime exception is thrown

      */

     abstract protected ClientDescriptor getClientDescriptor(RequestType originalRequest) throws ControllerException;

     /**

      * Inspector of the dispatcher assigned to this channel.

      * 

      * @return theDispatcher attribute

      */

     protected IDIFDispatcher getDispatcher()

     {

         return DIFIoCRegistry.getRegistry().getImplementation(IDIFDispatcher.class, getChannelID());

     }

     /**

      * Inspector of the dispatcher assigned to this channel.

      * 

      * @return theDispatcher attribute

      */

     protected IDispatcherErrorHandler getErrorHandler()

     {

         return DIFIoCRegistry.getRegistry().getImplementation(IDispatcherErrorHandler.class, getChannelID());

     }

     /**

      * @see pt.digitalis.dif.controller.interfaces.IChAL#serve(java.lang.Object, java.lang.Object,

      *      pt.digitalis.dif.controller.objects.RESTAction)

      * @param originalRequest

      *            the original request object

      * @param finalResponse

      *            the final response object

      * @param restAction

      *            the REST action, if specified

      * @return the processed DIFResponse

      */

     @Trace(metricName = "DIF:ChAL:Serve", dispatcher = true)

     public IDIFResponse serve(RequestType originalRequest, ResponseType finalResponse, RESTAction restAction)

     {

         IDIFResponse difResponse = null;

         IDIFRequest difRequest = null;

         try

         {

             difRequest = translateRequest(originalRequest);

             difRequest.setRestAction(restAction);

             // Initializes the client descriptor if ins't filled. The translateRequest is responsible for filling it.

             if (difRequest.getClient() == null)

                 difRequest.setClient(getClientDescriptor(originalRequest));

             if (validateRequest(originalRequest))

             {

                 difResponse = getDispatcher().dispatch(difRequest);

                 // Fail-over. Should never return null.

                 if (difResponse == null)

                     difResponse = getErrorHandler().getDefaultErrorResponse(difRequest, null);

             }

             else

                 difResponse = getErrorHandler().getDefaultErrorResponse(difRequest, null);

         }

         catch (BusinessFlowException exception)

         {

             difResponse = getErrorHandler().processException(difRequest, exception);

         }

         catch (RuntimeException exception)

         {

             difResponse = getErrorHandler().processException(difRequest, exception);

         }

         catch (ControllerException exception)

         {

             difResponse = getErrorHandler().processException(difRequest, exception);

         }

         this.publish(difResponse, originalRequest, finalResponse);

         return difResponse;

     }

     /**

      * Validates the original request. It can be used to check if a particular request is valid for the channel. It may

      * also perform other validations, as the request parameters integrity.

      * 

      * @param originalRequest

      *            The original request received from the client.

      * @return T case the request is well formed, F otherwise

      * @throws ControllerException

      *             when any runtime exception is thrown

      */

     abstract protected boolean validateRequest(RequestType originalRequest) throws ControllerException;

 }