/*
    * $Id$
    *
    * 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.struts.apps.scriptingmailreader.plugin;
  
  
  import java.io.BufferedInputStream;
  import java.io.BufferedOutputStream;
  import java.io.File;
  import java.io.FileOutputStream;
  
  import jakarta.servlet.ServletException;
  
  import org.apache.struts.action.ActionServlet;
  import org.apache.struts.action.PlugIn;
  import org.apache.struts.apps.mailreader.dao.impl.memory.MemoryUserDatabase;
  import org.apache.struts.apps.scriptingmailreader.Constants;
  import org.apache.struts.config.ModuleConfig;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * <p><strong>MemoryDatabasePlugIn</strong> initializes and finalizes the
   * persistent storage of User and Subscription information for the Struts
   * Demonstration Application, using an in-memory database backed by an
   * XML file.</p>
   *
   * <p><strong>IMPLEMENTATION WARNING</strong> - If this web application is run
   * from a WAR file, or in another environment where reading and writing of the
   * web application resource is impossible, the initial contents will be copied
   * to a file in the web application temporary directory provided by the
   * container.  This is for demonstration purposes only - you should
   * <strong>NOT</strong> assume that files written here will survive a restart
   * of your servlet container.</p>
   *
   * @author Craig R. McClanahan
   * @version $Rev$ $Date$
   */
  
  public final class MemoryDatabasePlugIn implements PlugIn {
  
  
      // ----------------------------------------------------- Instance Variables
  
  
      /**
       * The {@link MemoryUserDatabase} object we construct and make available.
       */
      private MemoryUserDatabase database = null;
  
  
      /**
       * The {@code Log} instance for this class.
       */
      private final static Logger LOG =
          LoggerFactory.getLogger(MemoryDatabasePlugIn.class);
  
  
      /**
       * The {@link ActionServlet} owning this application.
       */
      private ActionServlet servlet = null;
  
  
      // ------------------------------------------------------------- Properties
  
  
      /**
       * The web application resource path of our persistent database
       * storage file.
       */
      private String pathname = "/WEB-INF/database.xml";
  
      public String getPathname() {
          return (this.pathname);
      }
  
      public void setPathname(String pathname) {
          this.pathname = pathname;
      }
 
 
     // --------------------------------------------------------- PlugIn Methods
 
 
     /**
      * Gracefully shut down this database, releasing any resources
      * that were allocated at initialization.
      */
     public void destroy() {
 
         LOG.info("Finalizing memory database plug in");
 
         if (database != null) {
             try {
                 database.close();
             } catch (Exception e) {
                 LOG.error("Closing memory database", e);
             }
         }
 
         servlet.getServletContext().removeAttribute(Constants.DATABASE_KEY);
         database = null;
         servlet = null;
         database = null;
     }
 
 
     /**
      * Initialize and load our initial database from persistent storage.
      *
      * @param servlet The ActionServlet for this web application
      * @param config  The ApplicationConfig for our owning module
      *
      * @throws ServletException if we cannot configure ourselves correctly
      */
     public void init(ActionServlet servlet, ModuleConfig config)
             throws ServletException {
 
         LOG.info("Initializing memory database plug in from '{}'",
             pathname);
 
         // Remember our associated configuration and servlet
         this.servlet = servlet;
 
         // Construct a new database and make it available
         database = new MemoryUserDatabase();
         try {
             String path = calculatePath();
             LOG.debug(" Loading database from '{}'", path);
             database.setPathname(path);
             database.open();
         } catch (Exception e) {
             LOG.error("Opening memory database", e);
             throw new ServletException("Cannot load database from '" +
                     pathname + "'", e);
         }
 
         // Make the initialized database available
         servlet.getServletContext().setAttribute(Constants.DATABASE_KEY,
                 database);
 
     }
 
 
     // --------------------------------------------------------- Public Methods
 
 
 
 
     // -------------------------------------------------------- Private Methods
 
 
     /**
      * Calculate and return an absolute pathname to the XML file to contain
      * our persistent storage information.
      *
      * @throws Exception if an input/output error occurs
      */
     private String calculatePath() throws Exception {
 
         // Can we access the database via file I/O?
         String path = servlet.getServletContext().getRealPath(pathname);
         if (path != null) {
             return (path);
         }
 
         // Does a copy of this file already exist in our temporary directory
         File dir = (File)
                 servlet.getServletContext().getAttribute
                         ("jakarta.servlet.context.tempdir");
         File file = new File(dir, "struts-example-database.xml");
         if (file.exists()) {
             return (file.getAbsolutePath());
         }
 
         // Copy the static resource to a temporary file and return its path
         try (BufferedInputStream bis = new BufferedInputStream(
                 servlet.getServletContext().getResourceAsStream(pathname), 1024);
                 BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(file), 1024)) {
 
             byte buffer[] = new byte[1024];
             while (true) {
                 int n = bis.read(buffer);
                 if (n <= 0) {
                     break;
                 }
                 bos.write(buffer, 0, n);
             }
         }
 
         return (file.getAbsolutePath());
 
     }
 }