package com.atlassian.plugins.rest.module.filter;
   
   import com.sun.jersey.spi.container.ContainerRequest;
   import com.sun.jersey.spi.container.ContainerRequestFilter;
   import org.apache.commons.lang.StringUtils;
   
   import javax.ws.rs.core.MediaType;
   import javax.ws.rs.core.MultivaluedMap;
   import javax.ws.rs.ext.Provider;
  import java.util.HashSet;
  import java.util.Set;
  
  import static javax.ws.rs.core.HttpHeaders.ACCEPT;
  import static javax.ws.rs.core.MediaType.APPLICATION_ATOM_XML;
  import static javax.ws.rs.core.MediaType.APPLICATION_JSON;
  import static javax.ws.rs.core.MediaType.APPLICATION_XML;
  import static javax.ws.rs.core.MediaType.TEXT_HTML;
  import static javax.ws.rs.core.MediaType.TEXT_PLAIN;
  import static javax.ws.rs.core.MediaType.WILDCARD;
  
  /**
   * <p>This is a filter to "fix" user agents with broken {@code Accept} headers.</p> <p>When a client accepts {@code
   * text/html} we want it to be first in the header. This is because, it is likely that it is a browser and we then
   * believe that HTML is the best view to render.</p> <p>This was introduced specifically to make Jersey MVC work with
   * webkit based browsers which by default have their accept header set to {@code application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*\/*;q=0.5}</p>
   * <p>The "fix" is to prepend {@code text/html} content type in the {@code Accept} header if it exists anywhere (else)
   * in the header.</p>
   * <p/>
   * <p>When a client accepts {@link MediaType#WILDCARD} (IE) we want to prepend it with {@code text/html}.
   */
  @Provider
  public class AcceptHeaderJerseyMvcFilter implements ContainerRequestFilter {
      static final Set<String> ACCEPTED_CONTENT_TYPES = new HashSet<String>() {{
          add(TEXT_PLAIN);
          add(TEXT_HTML);
          add(TEXT_HTML);
          add(APPLICATION_JSON);
          add(APPLICATION_XML);
          add(APPLICATION_ATOM_XML);
      }};
  
  
      public ContainerRequest filter(final ContainerRequest request) {
          final MultivaluedMap<String, String> requestHeaders = request.getRequestHeaders();
          final String acceptHeader = requestHeaders.getFirst(ACCEPT); // there should only be one Accept header
  
          String fixedHeader = addAppXmlWhenWildcardOnly(acceptHeader);
          fixedHeader = moveTextHtmlToFront(fixedHeader);
  
          if (acceptHeader != null && !acceptHeader.equals(fixedHeader)) {
              requestHeaders.putSingle(ACCEPT, fixedHeader);
          }
  
          return request;
      }
  
      private String addAppXmlWhenWildcardOnly(final String acceptHeader) {
          if (StringUtils.contains(acceptHeader, WILDCARD)) {
              for (String contentType : ACCEPTED_CONTENT_TYPES) {
                  if (StringUtils.contains(acceptHeader, contentType)) {
                      return acceptHeader;
                  }
              }
              return APPLICATION_XML + "," + acceptHeader;
          }
          return acceptHeader;
      }
  
      private String moveTextHtmlToFront(final String acceptHeader) {
          if ((StringUtils.contains(acceptHeader, TEXT_HTML) || StringUtils.contains(acceptHeader, WILDCARD))
                  && !StringUtils.startsWith(acceptHeader, TEXT_HTML)) {
              return TEXT_HTML + "," + acceptHeader;
          }
          return acceptHeader;
      }
  }