/*
    * Copyright 2017 LINE Corporation
    *
    * LINE Corporation licenses this file to you 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:
    *
    *   https://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.
   */
  
  package com.linecorp.centraldogma.server.internal.api.converter;
  
  import javax.annotation.Nullable;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.fasterxml.jackson.core.JsonProcessingException;
  import com.google.common.collect.Iterables;
  
  import com.linecorp.armeria.common.HttpData;
  import com.linecorp.armeria.common.HttpHeaders;
  import com.linecorp.armeria.common.HttpMethod;
  import com.linecorp.armeria.common.HttpRequest;
  import com.linecorp.armeria.common.HttpResponse;
  import com.linecorp.armeria.common.HttpStatus;
  import com.linecorp.armeria.common.MediaType;
  import com.linecorp.armeria.common.RequestContext;
  import com.linecorp.armeria.common.ResponseHeaders;
  import com.linecorp.armeria.common.ResponseHeadersBuilder;
  import com.linecorp.armeria.server.ServiceRequestContext;
  import com.linecorp.armeria.server.annotation.ResponseConverterFunction;
  import com.linecorp.centraldogma.internal.Jackson;
  import com.linecorp.centraldogma.server.internal.api.HttpApiUtil;
  
  /**
   * A default {@link ResponseConverterFunction} of HTTP API.
   */
  public final class HttpApiResponseConverter implements ResponseConverterFunction {
  
      private static final Logger logger = LoggerFactory.getLogger(HttpApiResponseConverter.class);
  
      @Override
      public HttpResponse convertResponse(ServiceRequestContext ctx, ResponseHeaders headers,
                                          @Nullable Object resObj,
                                          HttpHeaders trailingHeaders) throws Exception {
          try {
              final HttpRequest request = RequestContext.current().request();
              if (resObj == null || HttpMethod.DELETE == request.method() ||
                  (resObj instanceof Iterable && Iterables.size((Iterable<?>) resObj) == 0)) {
                  return HttpResponse.of(HttpStatus.NO_CONTENT);
              }
  
              final ResponseHeaders resHeaders;
              if (headers.contentType() == null) {
                  final ResponseHeadersBuilder builder = headers.toBuilder();
                  builder.contentType(MediaType.JSON_UTF_8);
                  resHeaders = builder.build();
              } else {
                  resHeaders = headers;
              }
  
              final HttpData httpData = HttpData.wrap(Jackson.writeValueAsBytes(resObj));
              return HttpResponse.of(resHeaders, httpData, trailingHeaders);
          } catch (JsonProcessingException e) {
              logger.debug("Failed to convert a response:", e);
              return HttpApiUtil.newResponse(ctx, HttpStatus.INTERNAL_SERVER_ERROR, e);
          }
      }
  }