/*
 * This file is part of the Meeds project (https://meeds.io/).
 * Copyright (C) 2020 Meeds Association
 * contact@meeds.io
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser 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
 * Lesser General Public License for more details.
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */
package org.exoplatform.services.rest.servlet;

import org.exoplatform.container.ExoContainer;
import org.exoplatform.container.ExoContainerContext;
import org.exoplatform.container.component.ComponentRequestLifecycle;
import org.exoplatform.container.component.RequestLifeCycle;
import org.exoplatform.container.context.ContextManagerListener;
import org.exoplatform.container.web.AbstractHttpServlet;
import org.exoplatform.services.log.ExoLogger;
import org.exoplatform.services.log.Log;
import org.exoplatform.services.rest.Connector;
import org.exoplatform.services.rest.ContainerResponseWriter;
import org.exoplatform.services.rest.GenericContainerResponse;
import org.exoplatform.services.rest.RequestHandler;
import org.exoplatform.services.rest.impl.ContainerResponse;
import org.exoplatform.services.rest.impl.EnvironmentContext;
import org.exoplatform.services.rest.impl.header.HeaderHelper;

import java.io.IOException;
import java.io.OutputStream;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.ws.rs.ext.MessageBodyWriter;

/**
 * This servlet is front-end for the REST engine.
 *
 * @author <a href="mailto:andrew00x@gmail.com">Andrey Parfonov</a>
 * @version $Id: $
 */
public class RestServlet extends AbstractHttpServlet implements Connector
{

   private static final Log LOG = ExoLogger.getLogger("exo.ws.rest.core.RestServlet");

   /**
    * Generated by Eclipse.
    */
   private static final long serialVersionUID = 2152962763071591181L;

  private List<ComponentRequestLifecycle> transactionalServices = null;

   /**
    * {@inheritDoc}
    */
   @Override
   protected void afterInit(ServletConfig config) throws ServletException
   {
      // Register the listener if needed
      ContextManagerListener.registerIfNeeded(getContainer(), config.getServletContext());
   }

   /**
    * {@inheritDoc}
    */
   @Override
   protected void onService(ExoContainer container, HttpServletRequest httpRequest, HttpServletResponse httpResponse)
      throws IOException, ServletException
   {

      ExoContainerContext.setCurrentContainer(getContainer());
      RequestLifeCycle.begin(getContainer());

      RequestHandler requestHandler = (RequestHandler)container.getComponentInstanceOfType(RequestHandler.class);

      EnvironmentContext env = new EnvironmentContext();
      env.put(HttpServletRequest.class, httpRequest);
      env.put(HttpServletResponse.class, httpResponse);
      env.put(ServletConfig.class, config);
      env.put(ServletContext.class, getServletContext());

      try
      {
         EnvironmentContext.setCurrent(env);
         ServletContainerRequest request = new ServletContainerRequest(httpRequest);
         ContainerResponse response = new ContainerResponse(new ServletContainerResponseWriter(httpResponse));
         requestHandler.handleRequest(request, response);
      }
      catch (Exception e)
      {
        if (e.getClass().getName().equals("org.apache.catalina.connector.ClientAbortException")) {
          LOG.debug("Write socket error!", e);
        } else {
          LOG.warn("An error occurred while calling REST endpoint {}, method: {}",
                   httpRequest.getRequestURI(),
                   httpRequest.getMethod(),
                   e);
        }
      }
      finally
      {
         Map<Object, Throwable> results = RequestLifeCycle.end();
         for (Entry<Object, Throwable> entry : results.entrySet())
         {
            if (entry.getValue() != null)
            {
               LOG.error("An error occurred while calling the method endRequest on " + entry.getKey(), entry.getValue());
            }
         }
         EnvironmentContext.setCurrent(null);
         for (ComponentRequestLifecycle service : getTransactionalServices()) {
           if (service.isStarted(getContainer())) {
             if (LOG.isDebugEnabled()) {
               LOG.debug("The service {} didn't called endRequest, uri = {}, http method = {}. Commit transaction anyway.",
                         service.getClass().getName(),
                         httpRequest.getRequestURI(),
                         httpRequest.getMethod());
             }
             service.endRequest(getContainer());
             if (service.isStarted(getContainer())) {
               LOG.error("The service {} didn't ended properly even after calling endRequest",
                         service.getClass().getName(),
                         httpRequest.getRequestURI(),
                         httpRequest.getMethod());
             }
           }
         }
      }
   }

   /**
    * See {@link ContainerResponseWriter}.
    */
   class ServletContainerResponseWriter implements ContainerResponseWriter
   {

      /**
       * See {@link HttpServletResponse}.
       */
      private HttpServletResponse servletResponse;

      /**
       * @param response HttpServletResponse
       */
      ServletContainerResponseWriter(HttpServletResponse response)
      {
         this.servletResponse = response;
      }

      /**
       * {@inheritDoc}
       */
      @SuppressWarnings("unchecked")
      public void writeBody(GenericContainerResponse response, MessageBodyWriter entityWriter) throws IOException
      {
         Object entity = response.getEntity();
         if (entity != null)
         {
            OutputStream out = servletResponse.getOutputStream();
            entityWriter.writeTo(entity, entity.getClass(), response.getEntityType(), null, response.getContentType(),
               response.getHttpHeaders(), out);
            out.flush();
         }
      }

      /**
       * {@inheritDoc}
       */
      public void writeHeaders(GenericContainerResponse response) throws IOException
      {
         if (servletResponse.isCommitted())
         {
            return;
         }

         servletResponse.setStatus(response.getStatus());

         if (response.getHttpHeaders() != null)
         {
            // content-type and content-length should be preset in headers
            for (Map.Entry<String, List<Object>> e : response.getHttpHeaders().entrySet())
            {
               String name = e.getKey();
               for (Object o : e.getValue())
               {
                  String value = null;
                  if (o != null && (value = HeaderHelper.getHeaderAsString(o)) != null)
                  {
                     servletResponse.addHeader(name, value);
                  }
               }
            }
         }
      }
   }

  public List<ComponentRequestLifecycle> getTransactionalServices() {
    if (transactionalServices == null) {
      transactionalServices = getContainer().getComponentInstancesOfType(ComponentRequestLifecycle.class);
    }
    return transactionalServices;
  }
}
