/*
    * #%L
    * wcm.io
    * %%
    * Copyright (C) 2015 wcm.io
    * %%
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   * #L%
   */
  package io.wcm.caravan.io.http.impl.servletclient;
  
  import java.io.IOException;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.ConcurrentMap;
  import java.util.concurrent.ConcurrentSkipListMap;
  
  import javax.servlet.Servlet;
  import javax.servlet.ServletException;
  
  import org.apache.felix.scr.annotations.Component;
  import org.apache.felix.scr.annotations.Reference;
  import org.apache.felix.scr.annotations.ReferenceCardinality;
  import org.apache.felix.scr.annotations.ReferencePolicy;
  import org.apache.felix.scr.annotations.Service;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.google.common.collect.Sets;
  
  import io.wcm.caravan.io.http.CaravanHttpClient;
  import io.wcm.caravan.io.http.IllegalResponseRuntimeException;
  import io.wcm.caravan.io.http.RequestFailedRuntimeException;
  import io.wcm.caravan.io.http.impl.CaravanHttpServiceConfigValidator;
  import io.wcm.caravan.io.http.request.CaravanHttpRequest;
  import io.wcm.caravan.io.http.response.CaravanHttpResponse;
  import rx.Observable;
  
  /**
   * Client which executes {@link Servlet}s registered in the same server directly without HTTP. Ignores fallbacks.
   */
  @Component
  @Service(ServletHttpClient.class)
  public class ServletHttpClient implements CaravanHttpClient {
  
    private static final Logger LOG = LoggerFactory.getLogger(ServletHttpClient.class);
  
    @Reference(referenceInterface = Servlet.class, cardinality = ReferenceCardinality.OPTIONAL_MULTIPLE, policy = ReferencePolicy.DYNAMIC)
    private final ConcurrentMap<String, Servlet> servlets = new ConcurrentSkipListMap<>();
  
    private final Set<String> failedServices = Sets.newHashSet();
    protected void bindServlet(Servlet servlet, Map<String, Object> config) {
      String serviceId = (String)config.get("alias");
      if (serviceId != null) {
        servlets.put(serviceId, servlet);
      }
    }
  
    protected void unbindServlet(Servlet servle, Map<String, Object> config) {
      String serviceId = (String)config.get("alias");
      if (serviceId != null) {
        servlets.remove(serviceId);
      }
    }
  
    @Override
    public Observable<CaravanHttpResponse> execute(CaravanHttpRequest request) {
      return Observable.just(request.getServiceId())
          .map(serviceId -> getServlet(serviceId))
          .map(servlet -> executeServlet(servlet, request));
    }
  
    @Override
    public Observable<CaravanHttpResponse> execute(CaravanHttpRequest request, Observable<CaravanHttpResponse> fallback) {
      return execute(request);
    }
  
    @Override
    public boolean hasValidConfiguration(String serviceId) {
      return servlets.containsKey(serviceId) && !failedServices.contains(serviceId);
    }
  
    private Servlet getServlet(String serviceId) {
  
      Servlet servlet = servlets.get(serviceId);
      if (servlet == null) {
        throw new IllegalStateException("No local servlet registered for " + serviceId);
      }
      return servlet;
 
   }
 
   private CaravanHttpResponse executeServlet(Servlet servlet, CaravanHttpRequest request) {
 
     LOG.debug("Execute: {},\n{}", request.toString(), request.getCorrelationId());
     HttpServletRequestMapper requestMapper = new HttpServletRequestMapper(request);
     HttpServletResponseMapper responseMapper = new HttpServletResponseMapper();
     try {
       servlet.service(requestMapper, responseMapper);
       CaravanHttpResponse response = responseMapper.getResponse();
 
       int status = response.status();
       boolean throwExceptionForStatus500 = CaravanHttpServiceConfigValidator.throwExceptionForStatus500(request.getServiceId());
       if (status >= 500 && throwExceptionForStatus500) {
         String requestUrl = request.getUrl();
         String responseBody = response.body().asString();
         throw new IllegalResponseRuntimeException(request, requestUrl, status, responseBody,
           "Executing '" + requestUrl + "' failed: " + responseBody);
       }
       return response;
     }
     catch (NotSupportedByRequestMapperException ex) {
       failedServices.add(request.getServiceId());
       throw ex;
     }
     catch (ServletException | IOException ex) {
       throw new RequestFailedRuntimeException(request, ex.getMessage(), ex);
     }
 
   }
 
 }