package com.atlassian.plugins.rest.module;
   
   import com.atlassian.plugin.osgi.factory.OsgiPlugin;
   import com.google.common.base.Preconditions;
   import com.sun.jersey.api.core.ResourceConfig;
   import com.sun.jersey.spi.container.WebApplication;
   import com.sun.jersey.spi.container.servlet.ServletContainer;
   import com.sun.jersey.spi.container.servlet.WebConfig;
   import org.apache.commons.lang.StringUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import javax.servlet.Filter;
  import javax.servlet.FilterChain;
  import javax.servlet.FilterConfig;
  import javax.servlet.ServletException;
  import javax.servlet.ServletRequest;
  import javax.servlet.ServletResponse;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import javax.ws.rs.core.UriBuilder;
  import java.io.IOException;
  import java.net.URI;
  import java.util.Map;
  
  /**
   * A delegating servlet that swaps the context class loader with a {@link ChainingClassLoader} that delegates to both
   * the class loader of the {@link RestModuleDescriptor} and the current context class loader.
   */
  class RestDelegatingServletFilter implements Filter {
      private static final Logger log = LoggerFactory.getLogger(RestDelegatingServletFilter.class);
      /**
       * Helper object for installing and un-installing the SLF4J bridge.
       */
      private static final Slf4jBridge.Helper SLF4J_BRIDGE = Slf4jBridge.createHelper();
  
      /**
       * Overriden servlet container to use our own {@link OsgiResourceConfig}.
       */
      private final ServletContainer servletContainer;
      private final ResourceConfigManager resourceConfigManager;
  
      /**
       * This class loader is set as the thread context class loader whenever we are calling into Jersey. We need to reuse
       * the same class loader every time because when this filter is initialised it sets up the JUL->SLF4J bridge (the
       * same one that allows ).
       *
       * The thread context class loader (TCCL) is set to this class loader when calling into Jersey. We keep a reference
       * to it as opposed to creating a new one in every invocation because Jersey uses java.util.logging, which on
       * Tomcat is implemented by JULI.
       */
      private volatile ClassLoader chainingClassLoader;
  
      RestDelegatingServletFilter(OsgiPlugin plugin, RestApiContext restContextPath) {
          resourceConfigManager = new ResourceConfigManager(plugin, plugin.getBundle());
          this.servletContainer = new JerseyOsgiServletContainer(plugin, restContextPath, resourceConfigManager);
      }
  
      public void init(FilterConfig config) throws ServletException {
          initChainingClassLoader();
          initServletContainer(config);
      }
  
      public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
          ClassLoader currentThreadClassLoader = Thread.currentThread().getContextClassLoader();
          Thread.currentThread().setContextClassLoader(chainingClassLoader);
          try {
              servletContainer.doFilter(request, response, chain);
          } finally {
              Thread.currentThread().setContextClassLoader(currentThreadClassLoader);
          }
      }
  
      public void destroy() {
          destroyServletContainer();
          resourceConfigManager.destroy();
      }
  
      private void initChainingClassLoader() {
          chainingClassLoader = new ChainingClassLoader(RestModuleDescriptor.class.getClassLoader(), Thread.currentThread().getContextClassLoader());
      }
  
      private void initServletContainer(FilterConfig config) throws ServletException {
          ClassLoader currentThreadClassLoader = Thread.currentThread().getContextClassLoader();
          Thread.currentThread().setContextClassLoader(chainingClassLoader);
          try {
              SLF4J_BRIDGE.install();
              servletContainer.init(config);
          } finally {
              Thread.currentThread().setContextClassLoader(currentThreadClassLoader);
          }
      }
  
      private void destroyServletContainer() {
          ClassLoader currentThreadClassLoader = Thread.currentThread().getContextClassLoader();
          Thread.currentThread().setContextClassLoader(chainingClassLoader);
          try {
              servletContainer.destroy();
              SLF4J_BRIDGE.uninstall();
         } finally {
             Thread.currentThread().setContextClassLoader(currentThreadClassLoader);
         }
     }
 
     /**
      *
      */
     private static class JerseyOsgiServletContainer extends ServletContainer {
         private final OsgiPlugin plugin;
         private final RestApiContext restApiContext;
         private final ResourceConfigManager resourceConfigManager;
 
         private static final String PARAM_EXTENSION_FILTER_EXCLUDES = "extension.filter.excludes";
 
         public JerseyOsgiServletContainer(OsgiPlugin plugin, RestApiContext restApiContext, final ResourceConfigManager resourceConfigManager) {
             this.resourceConfigManager = Preconditions.checkNotNull(resourceConfigManager);
             this.plugin = Preconditions.checkNotNull(plugin);
             this.restApiContext = Preconditions.checkNotNull(restApiContext);
         }
 
         @Override
         protected ResourceConfig getDefaultResourceConfig(Map<String, Object> props, WebConfig webConfig) throws ServletException {
             // get the excludes parameter: support the old param name for Atlassian Gadgets
             final String deprecatedName = "com.atlassian.plugins.rest.module.filter.ExtensionJerseyFilter" + "#excludes";
             final String excludeParam = webConfig.getInitParameter(deprecatedName) != null ?
                     webConfig.getInitParameter(deprecatedName) : webConfig.getInitParameter(PARAM_EXTENSION_FILTER_EXCLUDES);
 
             final String[] excludes = StringUtils.split(excludeParam, " ,;");
 
             return resourceConfigManager.createResourceConfig(props, excludes, restApiContext.getPackages());
         }
 
         @Override
         public void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain)
                 throws IOException, ServletException {
             // This is overridden so that we can change the base URI, and keep the context path the same
             String baseUriPath;
             if (request.getRequestURI().contains(restApiContext.getPathToLatest())) {
                 baseUriPath = request.getContextPath() + restApiContext.getPathToLatest();
                 // TODO Remove this when REST-159 is fixed
                 // Added logging to help find the root cause of REST-159
                 log.debug("Setting base uri for REST to 'latest'");
                 log.debug("Incoming URI : " + request.getRequestURI());
             } else {
                 baseUriPath = request.getContextPath() + restApiContext.getPathToVersion();
             }
             final UriBuilder absoluteUriBuilder = UriBuilder.fromUri(request.getRequestURL().toString());
 
             final URI baseUri = absoluteUriBuilder.replacePath(baseUriPath).path("/").build();
 
             final URI requestUri = absoluteUriBuilder.replacePath(request.getRequestURI()).replaceQuery(
                     request.getQueryString()).build();
 
             service(baseUri, requestUri, request, response);
         }
 
         @Override
         protected void initiate(ResourceConfig resourceConfig, WebApplication webApplication) {
             webApplication.initiate(resourceConfig, new OsgiComponentProviderFactory(resourceConfig, plugin));
         }
     }
 }