/*
 * Data Hub Service (DHuS) - For Space data distribution.
 * Copyright (C) 2013,2014,2015,2016 GAEL Systems
 *
 * This file is part of DHuS software sources.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
package fr.gael.dhus.olingo.v1;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.olingo.odata2.api.ODataDebugCallback;
import org.apache.olingo.odata2.api.ODataDebugResponseWrapperCallback;
import org.apache.olingo.odata2.api.commons.HttpStatusCodes;
import org.apache.olingo.odata2.api.ep.EntityProvider;
import org.apache.olingo.odata2.api.exception.ODataApplicationException;
import org.apache.olingo.odata2.api.exception.ODataException;
import org.apache.olingo.odata2.api.processor.ODataContext;
import org.apache.olingo.odata2.api.processor.ODataErrorCallback;
import org.apache.olingo.odata2.api.processor.ODataErrorContext;
import org.apache.olingo.odata2.api.processor.ODataRequest;
import org.apache.olingo.odata2.api.processor.ODataResponse;
import org.apache.olingo.odata2.api.uri.UriInfo;

/** This class implements some callbacks to log error, exception and debug messages. */
class ServiceLogger implements ODataDebugCallback,
      ODataDebugResponseWrapperCallback, ODataErrorCallback
{

   private static final Logger LOGGER = LogManager.getLogger(ServiceLogger.class);

   /**
    * Enables the debug output in the response when the request has its
    * `odata-debug` set to 'json' or 'html'.
    */
   @Override
   public boolean isDebugEnabled()
   {
      return true;
   }

   /**
    * Logs the request URIs. Always logs at DEBUG level except when an exception
    * occurs. From ODataDebugResponseWrapperCallback.
    */
   @Override
   public ODataResponse handle(ODataContext ctx, ODataRequest rq,
         ODataResponse rsp, UriInfo uri, Exception e)
   {
      // I do not print the exception here; exceptions are managed by the
      // `handleError` method below
      try
      {
         // Always logs at DEBUG level except when an exception occurs
         if (e == null || e instanceof ExpectedException)
         {
            if(e instanceof ExpectedException.MediaRegulationException)
            {
               LOGGER.warn("Uri {}: {}", ctx.getPathInfo().getRequestUri(), e.getMessage());
            }
            else
            {
               LOGGER.debug("Uri {}", ctx.getPathInfo().getRequestUri());
            }
         }
         else
         {
            LOGGER.error("Uri {}: {}", ctx.getPathInfo().getRequestUri(), e.getMessage(), e);
         }
      }
      catch (ODataException e1)
      {
         LOGGER.fatal("An exception occured while logging an ODataResponse", e1);
      }
      return rsp;
   }

   /**
    * Handle an error with adding the error message in the stream thanks to 
    * {@link EntityProvider#writeErrorDocument(ODataErrorContext)} method, but
    * when the response stream is not identified as binary stream (uri contains
    * $value), no ascii message is inserted into the stream.
    */
   @Override
   public ODataResponse handleError(ODataErrorContext ctx) throws ODataApplicationException
   {
      // Compute the error message
      String message = ctx.getMessage();
      if (ctx.getException() != null)
      {
         message = ctx.getException().getClass().getSimpleName();
         if (ctx.getException().getMessage() != null)
         {
            message += " : " + ctx.getException().getMessage();
         }
         else if (ctx.getMessage() != null)
         {
            message += " : " + ctx.getMessage();
         }
      }

      // Suppress in-stream error messages
      // ExpectedException are never thrown while streaming the payload
      if (ctx.getRequestUri().toString().endsWith("$value")
            && (ctx.getException() == null || ctx.getException() instanceof ExpectedException))
      {
         return ODataResponse
               .header("cause-message", message)
               .status(HttpStatusCodes.INTERNAL_SERVER_ERROR)
               .build();
      }
      return ODataResponse
            .fromResponse(EntityProvider.writeErrorDocument(ctx))
            .header("cause-message", message)
            .build();
   }

}