package com.atlassian.plugins.rest.common.filter;
   
   import com.atlassian.annotations.tenancy.TenantAware;
   import com.google.common.collect.ImmutableMap;
   import com.sun.jersey.spi.container.ContainerRequest;
   import com.sun.jersey.spi.container.ContainerRequestFilter;
   import org.apache.commons.lang.StringUtils;
   import org.apache.commons.lang.Validate;
   
  import javax.ws.rs.core.HttpHeaders;
  import javax.ws.rs.core.UriBuilder;
  import javax.ws.rs.ext.Provider;
  import java.net.URI;
  import java.util.Collection;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.regex.Pattern;
  
  import static com.atlassian.annotations.tenancy.TenancyScope.TENANTLESS;
  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;
  
  /**
   * <p>A filter to handle URI with extensions. It will set the correct accept header for each extension and remove the extension
   * from the URI to allow for normal processing of the request.</p>
   * <p>Currently supported extension and their matching headers are defined in {@link #EXTENSION_TO_ACCEPT_HEADER the extension to header mapping}.</p>
   * <p>One can exclude URIs from being processed by this filter. Simply create the filter with a collection of {@link Pattern patterns} to be excluded.</p>
   * <p><strong>Example:</strong> URI <code>http://localhost:8080/app/rest/my/resource.json</code> would be automatically mapped to URI <code>http://localhost:8080/app/rest/my/resource</code>
   * with its <code>accept</code> header set to <code>application/json</code></p>
   */
  @Provider
  public class ExtensionJerseyFilter implements ContainerRequestFilter {
      private static final String DOT = ".";
  
      private final Collection<Pattern> pathExcludePatterns;
  
      public ExtensionJerseyFilter() {
          pathExcludePatterns = new LinkedList<Pattern>();
      }
  
      public ExtensionJerseyFilter(Collection<String> pathExcludePatterns) {
          Validate.notNull(pathExcludePatterns);
          this.pathExcludePatterns = compilePatterns(pathExcludePatterns);
      }
  
      @TenantAware(TENANTLESS)
      final static Map<String, String> EXTENSION_TO_ACCEPT_HEADER = new ImmutableMap.Builder<String, String>()
              .put("txt", TEXT_PLAIN)
              .put("htm", TEXT_HTML)
              .put("html", TEXT_HTML)
              .put("json", APPLICATION_JSON)
              .put("xml", APPLICATION_XML)
              .put("atom", APPLICATION_ATOM_XML)
              .build();
  
      public ContainerRequest filter(ContainerRequest request) {
          // the path to the request without query params
          final String absolutePath = request.getAbsolutePath().toString();
  
          final String extension = StringUtils.substringAfterLast(absolutePath, DOT);
          if (shouldFilter("/" + StringUtils.difference(request.getBaseUri().toString(), absolutePath), extension)) {
              request.getRequestHeaders().putSingle(HttpHeaders.ACCEPT, EXTENSION_TO_ACCEPT_HEADER.get(extension));
              final String absolutePathWithoutExtension = StringUtils.substringBeforeLast(absolutePath, DOT);
              request.setUris(request.getBaseUri(), getRequestUri(absolutePathWithoutExtension, request.getQueryParameters()));
          }
          return request;
      }
  
      private boolean shouldFilter(String restPath, String extension) {
          for (Pattern pattern : pathExcludePatterns) {
              if (pattern.matcher(restPath).matches()) {
                  return false;
              }
          }
          return EXTENSION_TO_ACCEPT_HEADER.containsKey(extension);
      }
  
      private URI getRequestUri(String absolutePathWithoutExtension, Map<String, List<String>> queryParams) {
          final UriBuilder requestUriBuilder = UriBuilder.fromPath(absolutePathWithoutExtension);
          for (Map.Entry<String, List<String>> queryParamEntry : queryParams.entrySet()) {
              for (String value : queryParamEntry.getValue()) {
                  requestUriBuilder.queryParam(queryParamEntry.getKey(), value);
              }
          }
          return requestUriBuilder.build();
      }
  
      private Collection<Pattern> compilePatterns(Collection<String> pathExcludePatterns) {
          final Collection<Pattern> patterns = new LinkedList<Pattern>();
          for (String pattern : pathExcludePatterns) {
              patterns.add(Pattern.compile(pattern));
          }
          return patterns;
      }
  }