/*
    * Licensed to The Apereo Foundation under one or more contributor license
    * agreements. See the NOTICE file distributed with this work for additional
    * information regarding copyright ownership.
    *
    *
    * The Apereo Foundation licenses this file to you under the Educational
    * Community 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://opensource.org/licenses/ecl2.txt
   *
   * 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.opencastproject.rest;
  
  import org.opencastproject.util.MimeTypes;
  
  import org.apache.commons.codec.digest.DigestUtils;
  import org.apache.commons.io.IOUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URL;
  import java.util.Map;
  
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  /**
   * A static resource for registration with the http service.
   */
  public class StaticResource extends HttpServlet {
    /** The java.io.serialization uid */
    private static final long serialVersionUID = 1L;
  
    /** The logger */
    private static final Logger logger = LoggerFactory.getLogger(StaticResource.class);
  
    /** The classpath to search for the static resources */
    protected String classpath = null;
  
    /** The base URL for these static resources */
    protected String alias = null;
  
    /** The welcome file to redirect to, if only the alias is specified in the request */
    protected String welcomeFile = null;
  
    /** The enable spa redirect flag */
    protected boolean spaRedirect = false;
  
    /** The classloader to use to search for the static resources. */
    protected ClassLoader classloader = null;
  
    /**
     * Constructs a static resources.
     *
     * @param classpath
     *          the classpath to the static resources
     * @param alias
     *          the URL alias
     * @param welcomeFile
     *          the default welcome file
     */
    public StaticResource(ClassLoader classloader, String classpath, String alias, String welcomeFile) {
      this(classloader, classpath, alias, welcomeFile, false);
    }
  
    /**
     * Constructs a static resources.
     *
     * @param classpath
     *          the classpath to the static resources
     * @param alias
     *          the URL alias
     * @param welcomeFile
     *          the default welcome file
     * @param spaRedirect
     *          enable spa redirects
     */
    public StaticResource(ClassLoader classloader, String classpath, String alias, String welcomeFile,
        boolean spaRedirect) {
      this.classpath = classpath;
      this.alias = alias;
      this.welcomeFile = welcomeFile;
      this.classloader = classloader;
      this.spaRedirect = spaRedirect;
    }
 
   /**
    * Activates the static resource when it is instantiated using Declarative Services.
    *
    * @param componentProperties
    *          the DS component context
    */
   @SuppressWarnings("unchecked")
   public void activate(Map componentProperties) {
     if (welcomeFile == null) {
       welcomeFile = (String) componentProperties.get("welcome.file");
     }
     boolean welcomeFileSpecified = true;
     if (welcomeFile == null) {
       welcomeFileSpecified = false;
       welcomeFile = "index.html";
     }
     if (alias == null) {
       alias = (String) componentProperties.get("alias");
     }
     if (classpath == null) {
       classpath = (String) componentProperties.get("classpath");
     }
     logger.info("registering classpath:{} at {} with welcome file {} {}", classpath, alias, welcomeFile,
             welcomeFileSpecified ? "" : "(via default)");
   }
 
   public String getDefaultUrl() {
     return alias;
   }
 
   @Override
   public String toString() {
     return "StaticResource [alias=" + alias + ", classpath=" + classpath + ", welcome file=" + welcomeFile + "]";
   }
 
   @Override
   public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     String pathInfo = req.getPathInfo();
     String servletPath = req.getServletPath();
     String path = pathInfo == null ? servletPath : servletPath + pathInfo;
     logger.debug("handling path {}, pathInfo={}, servletPath={}", path, pathInfo, servletPath);
 
     // If the URL points to a "directory", redirect to the welcome file
     if ("/".equals(path) || alias.equals(path) || (alias + "/").equals(path)) {
       String redirectPath;
       if ("/".equals(alias)) {
         redirectPath = "/" + welcomeFile;
       } else {
         redirectPath = alias + "/" + welcomeFile;
       }
       String queryString = req.getQueryString();
       redirectPath += queryString != null ? "?" + queryString : "";
       logger.debug("redirecting {} to {}", path, redirectPath);
       resp.sendRedirect(redirectPath);
       return;
     }
 
     // Find and deliver the resource
     String classpathToResource;
     if (pathInfo == null) {
       if (!servletPath.equals(alias)) {
         classpathToResource = classpath + servletPath;
       } else {
         classpathToResource = classpath + "/" + welcomeFile;
       }
     } else {
       classpathToResource = classpath + pathInfo;
     }
 
     // Make sure we are using an absolute path
     if (!classpathToResource.startsWith("/")) {
       classpathToResource = "/" + classpathToResource;
     }
 
     // Try to load the resource from the classloader
     URL url = classloader.getResource(classpathToResource);
 
     // Support SPA path locations
     if (spaRedirect && url == null) {
       String spaRedirect = classpath + "/" + welcomeFile;
       logger.trace("using fallback {}", spaRedirect);
       url = classloader.getResource(spaRedirect);
     }
 
     if (url == null) {
       resp.sendError(404);
       return;
     }
 
     logger.debug("opening url {} {}", classpathToResource, url);
     try (InputStream in = url.openStream()) {
       String md5 = DigestUtils.md5Hex(in);
       if (md5.equals(req.getHeader("If-None-Match"))) {
         resp.setStatus(304);
         return;
       }
       resp.setHeader("ETag", md5);
     }
 
     String contentType = MimeTypes.getMimeType(url.getPath());
     if (!MimeTypes.DEFAULT_TYPE.equals(contentType)) {
       resp.setHeader("Content-Type", contentType);
     }
 
     try (InputStream in = url.openStream()) {
       IOUtils.copy(in, resp.getOutputStream());
     }
   }
 }