package com.atlassian.plugins.rest.module.json;
   
   import com.sun.jersey.spi.container.ContainerRequest;
   import com.sun.jersey.spi.container.ContainerResponse;
   import com.sun.jersey.spi.container.ContainerResponseFilter;
   import org.apache.commons.lang.StringUtils;
   import org.apache.commons.lang.Validate;
   
   import static javax.ws.rs.core.HttpHeaders.*;
  
  import javax.ws.rs.core.MediaType;
  import javax.ws.rs.core.MultivaluedMap;
  import javax.ws.rs.ext.Provider;
  
  @Provider
  public class JsonWithPaddingResponseFilter implements ContainerResponseFilter {
      public static final String ATLASSIAN_ALLOW_JSONP = "atlassian.allow.jsonp";
  
      private final String callbackFunctionParameterName;
  
      public JsonWithPaddingResponseFilter() {
          this("jsonp-callback");
      }
  
      public JsonWithPaddingResponseFilter(String callbackFunctionParameterName) {
          Validate.notEmpty(callbackFunctionParameterName);
          this.callbackFunctionParameterName = callbackFunctionParameterName;
      }
  
      public ContainerResponse filter(ContainerRequest request, ContainerResponse response) {
          if (isJsonWithPadding(request, response)) {
              response.setContainerResponseWriter(new JsonWithPaddingResponseAdapter(getCallbackFunction(request), response.getContainerResponseWriter()));
          }
          return response;
      }
  
      private boolean isJsonWithPadding(ContainerRequest request, ContainerResponse response) {
          return isJsonResponse(response) && isCallbackRequest(request);
      }
  
      private boolean isCallbackRequest(ContainerRequest request) {
          return StringUtils.isNotBlank(getCallbackFunction(request));
      }
  
      private String getCallbackFunction(ContainerRequest request) {
          return request.getQueryParameters().getFirst(callbackFunctionParameterName);
      }
  
      private boolean isJsonResponse(ContainerResponse response) {
          final MultivaluedMap<String, Object> httpHeaders = response.getHttpHeaders();
          return httpHeaders.containsKey(CONTENT_TYPE) && httpHeaders.getFirst(CONTENT_TYPE).equals(MediaType.APPLICATION_JSON_TYPE);
      }
  }