/*
    * $Id$
    *
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF 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
   *
   * http://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 org.apache.tiles.request.locale;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.JarURLConnection;
  import java.net.URI;
  import java.net.URISyntaxException;
  import java.net.URL;
  import java.net.URLConnection;
  import java.util.HashSet;
  import java.util.Locale;
  import java.util.Set;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import static java.lang.System.getProperty;
  import static java.util.Collections.unmodifiableSet;
  
  /**
   * A {@link PostfixedApplicationResource} that can be accessed through a URL.
   *
   * @version $Rev$ $Date$
   */
  
  public class URLApplicationResource extends PostfixedApplicationResource {
      /**
       * System parameter to specify additional remote protocols. If a url has a remote protocol, then any
       * {@link IOException} will be thrown directly. If a url has a local protocol, then any {@link IOException}
       * will be caught and transformed into a {@link FileNotFoundException}.
       */
      static final String REMOTE_PROTOCOLS_PROPERTY = "tiles.remoteProtocols";
      private static final Logger LOG = LoggerFactory.getLogger(URLApplicationResource.class);
      private static final Set<String> REMOTE_PROTOCOLS;
  
      static {
          REMOTE_PROTOCOLS = initRemoteProtocols();
      }
  
      /**
       * Creates an unmodifiable set of <em>remote</em> protocols which are used in {@link URL} objects, see {@link URL#getProtocol()}.
       * A url with a remote protocol establishes a network connection when its {@link URL#openConnection()} is being called.
       * The set will always contain the built-in remote protocols below:
       * <ul>
       *  <li><a href="http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/687fd7c7986d/src/share/classes/sun/net/www/protocol/ftp">ftp</a></li>
       *  <li><a href="http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/687fd7c7986d/src/share/classes/sun/net/www/protocol/http">http</a></li>
       *  <li><a href="http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/687fd7c7986d/src/share/classes/sun/net/www/protocol/https">https</a></li>
       *  <li><a href="http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/687fd7c7986d/src/share/classes/sun/net/www/protocol/mailto">mailto</a></li>
       *  <li><a href="http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/687fd7c7986d/src/share/classes/sun/net/www/protocol/netdoc">netdoc</a></li>
       * </ul>
       * It's possible, that your environment provides additional remote protocols because of following reasons:
       * <ul>
       *     <li>your application server adds more remote protocols, see its documentation for further details.</li>
       *     <li>your application supplies custom remote protocols trough its own {@link java.net.URLStreamHandlerFactory}
       *     (see following excellent <a href="https://stackoverflow.com/questions/26363573/registering-and-using-a-custom-java-net-url-protocol">explanation</a>
       *     for getting an idea how to do this)</li>
       * </ul>
       * If you need to use such extra remote protocols in Tiles, you may enhance the set via system property {@code tiles.remoteProtocols}. Suppose
       * you need to add your custom remote protocols "foo" and "bar". To do so, add following parameter to the command line (use ";" as separator):
       * <pre>
       *     -Dtiles.remoteProtocols=foo;bar
       * </pre>
       * The resulting set will then contain the built-in protocols plus "foo" and "bar".
       *
       * @return Unmodifiable set of remote protocols, never {@code null}
       */
      static Set<String> initRemoteProtocols() {
          Set<String> remoteProtocols = new HashSet<String>();
          remoteProtocols.add("ftp");
          remoteProtocols.add("http");
          remoteProtocols.add("https");
          remoteProtocols.add("mailto");
          remoteProtocols.add("netdoc");
  
          String protocolsProp = getProperty(REMOTE_PROTOCOLS_PROPERTY);
         if (protocolsProp != null) {
             for (String protocol : protocolsProp.split(";")) {
                 remoteProtocols.add(protocol.trim());
             }
         }
         return unmodifiableSet(remoteProtocols);
     }
 
     private static boolean isLocal(URL url) {
         return !REMOTE_PROTOCOLS.contains(url.getProtocol());
     }
 
     /** the URL where the contents can be found. */
     private final URL url;
     /** if the URL matches a file, this is the file. */
     private File file;
     /** if the URL points to a local resource */
     private final boolean local;
 
     /**
      * Creates a URLApplicationResource for the specified path that can be accessed through the specified URL.
      *
      * @param localePath the path including localization.
      * @param url the URL where the contents can be found.
      */
     public URLApplicationResource(String localePath, URL url) {
         super(localePath);
         this.url = url;
         if ("file".equals(url.getProtocol())) {
             file = getFile(url);
         }
         local = isLocal(url);
     }
 
     /**
      * Creates a URLApplicationResource for the specified path that can be accessed through the specified URL.
      *
      * @param path the path excluding localization.
      * @param locale the Locale.
      * @param url the URL where the contents can be found.
      */
     public URLApplicationResource(String path, Locale locale, URL url) {
         super(path, locale);
         this.url = url;
         if ("file".equals(url.getProtocol())) {
             file = getFile(url);
         }
         local = isLocal(url);
     }
 
     private URLConnection openConnection() throws IOException {
         try {
             return url.openConnection();
         } catch (IOException e) {
             // If the url points to a local resource but it cannot be
             // opened, then the resource actually does not exist. In this
             // case throw a FileNotFoundException
             if (local) {
                 FileNotFoundException fne = new FileNotFoundException(url.toString());
                 fne.initCause(e);
                 throw fne;
             }
             throw e;
         }
     }
 
     private static File getFile(URL url) {
         try {
             return new File(new URI(url.toExternalForm()).getSchemeSpecificPart());
         } catch (URISyntaxException e) {
             LOG.debug("Cannot translate URL to file name, expect a performance impact", e);
             return null;
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public InputStream getInputStream() throws IOException {
         if (file != null) {
             return new FileInputStream(file);
         } else {
             return openConnection().getInputStream();
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public long getLastModified() throws IOException {
         if (file != null) {
             return file.lastModified();
         } else {
             URLConnection connection = openConnection();
             if (connection instanceof JarURLConnection) {
                 return ((JarURLConnection) connection).getJarEntry().getTime();
             } else {
                 long result = connection.getLastModified();
                 return result;
             }
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public String toString() {
         return "Resource " + getLocalePath() + " at " + url.toString();
     }
 
     protected URL getURL(){
         return url;
     }
 
     protected File getFile(){
         return file;
     }
 }