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// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
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package org.apache.juneau.microservice;

import java.io.*;
import java.net.*;
import java.util.*;
import java.util.logging.*;

import javax.servlet.*;

import org.apache.juneau.*;
import org.apache.juneau.config.*;
import org.apache.juneau.config.event.*;
import org.apache.juneau.internal.*;
import org.apache.juneau.svl.*;
import org.apache.juneau.utils.*;
import org.eclipse.jetty.server.*;
import org.eclipse.jetty.server.Handler;
import org.eclipse.jetty.server.handler.*;
import org.eclipse.jetty.servlet.*;
import org.eclipse.jetty.xml.*;

/**
 * Entry point for Juneau microservice that implements a REST interface using Jetty on a single port.
 * 
 * <h5 class='topic'>Jetty Server Details</h5>
 * 
 * The Jetty server is created by the {@link #createServer()} method and started with the {@link #startServer()} method.
 * These methods can be overridden to provided customized behavior.
 * 
 * <h5 class='topic'>Defining REST Resources</h5>
 * 
 * Top-level REST resources are defined in the <code>jetty.xml</code> file as normal servlets.
 * 
 * <h5 class='topic'>Logging</h5>
 * 
 * Logging is initialized by the {@link #initLogging()} method.
 * This method can be overridden to provide customized logging behavior.
 * 
 * <h5 class='topic'>Lifecycle Listener Methods</h5>
 * Subclasses can optionally implement the following event listener methods:
 * <ul class='spaced-list'>
 *    <li>
 *       {@link #onStart()} - Gets executed before {@link #start()}.
 *    <li>
 *       {@link #onStop()} - Gets executed before {@link #stop()}.
 *    <li>
 *       {@link #onCreateServer()} - Gets executed before {@link #createServer()}.
 *    <li>
 *       {@link #onStartServer()} - Gets executed before {@link #startServer()}.
 *    <li>
 *       {@link #onPostStartServer()} - Gets executed after {@link #startServer()}.
 *    <li>
 *       {@link #onStopServer()} - Gets executed before {@link #stop()}.
 *    <li>
 *       {@link #onPostStopServer()} - Gets executed after {@link #stop()}.
 * </ul>
 */
public class RestMicroservice extends Microservice {
   
   Server server;
   private Object jettyXml;
   private final MessageBundle mb = MessageBundle.create(RestMicroservice.class, "Messages");
   
   private static volatile RestMicroservice INSTANCE;
   
   /**
    * Returns the Microservice instance.  
    * <p>
    * This method only works if there's only one Microservice instance in a JVM.  
    * Otherwise, it's just overwritten by the last call to {@link #RestMicroservice(String...)}.
    * 
    * @return The Microservice instance, or <jk>null</jk> if there isn't one.
    */
   public static RestMicroservice getInstance() {
      synchronized(RestMicroservice.class) {
         return INSTANCE;
      }
   }
   
   /**
    * Main method.
    * 
    * <p>
    * Subclasses must also implement this method!
    * 
    * @param args Command line arguments.
    * @throws Exception
    */
   public static void main(String[] args) throws Exception {
      new RestMicroservice(args).start().join();
   }

   /**
    * Constructor.
    * 
    * @param args Command line arguments.
    * @throws Exception
    */
   public RestMicroservice(String...args) throws Exception {
      super(args);
      setInstance(this);
   }
   
   private static void setInstance(RestMicroservice rm) {
      synchronized(RestMicroservice.class) {
         INSTANCE = rm;
      }
   }

   //--------------------------------------------------------------------------------
   // Methods implemented on Microservice API
   //--------------------------------------------------------------------------------

   @Override /* Microservice */
   public RestMicroservice start() throws Exception {
      super.start();
      createServer();
      startServer();
      startConsole();
      return this;
   }

   @Override /* Microservice */
   public RestMicroservice join() throws Exception {
      server.join();
      return this;
   }

   @Override /* Microservice */
   public RestMicroservice stop() {
      final Logger logger = getLogger();
      final MessageBundle mb2 = mb;
      Thread t = new Thread() {
         @Override /* Thread */
         public void run() {
            try {
               if (server.isStopping() || server.isStopped())
                  return;
               onStopServer();
               out(mb2, "StoppingServer");
               server.stop();
               out(mb2, "ServerStopped");
               onPostStopServer();
            } catch (Exception e) {
               logger.log(Level.WARNING, e.getLocalizedMessage(), e);
            }
         }
      };
      t.start();
      try {
         t.join();
      } catch (InterruptedException e) {
         e.printStackTrace();
      }
      super.stop();
      return this;
   }


   //--------------------------------------------------------------------------------
   // RestMicroservice API methods.
   //--------------------------------------------------------------------------------

   /**
    * Returns the port that this microservice started up on.
    * <p>
    * The value is determined by looking at the <code>Server/Connectors[ServerConnector]/port</code> value in the 
    * Jetty configuration.
    * 
    * @return The port that this microservice started up on.
    */
   public int getPort() {
      for (Connector c : getServer().getConnectors()) 
         if (c instanceof ServerConnector)
            return ((ServerConnector)c).getPort();
      throw new RuntimeException("Could not locate ServerConnector in Jetty server.");
   }
   
   /**
    * Returns the context path that this microservice is using.
    * <p>
    * The value is determined by looking at the <code>Server/Handlers[ServletContextHandler]/contextPath</code> value 
    * in the Jetty configuration.
    * 
    * @return The context path that this microservice is using.
    */
   public String getContextPath() {
      for (Handler h : getServer().getHandlers()) {
         if (h instanceof HandlerCollection) {
            for (Handler h2 : ((HandlerCollection)h).getChildHandlers())
               if (h2 instanceof ServletContextHandler) 
                  return ((ServletContextHandler)h2).getContextPath();
         }
         if (h instanceof ServletContextHandler) 
            return ((ServletContextHandler)h).getContextPath();
      }
      throw new RuntimeException("Could not locate ServletContextHandler in Jetty server.");
   }
   
   /**
    * Returns whether this microservice is using <js>"http"</js> or <js>"https"</js>.
    * <p>
    * The value is determined by looking for the existence of an SSL Connection Factorie by looking for the
    * <code>Server/Connectors[ServerConnector]/ConnectionFactories[SslConnectionFactory]</code> value in the Jetty
    * configuration.
    * 
    * @return Whether this microservice is using <js>"http"</js> or <js>"https"</js>.
    */
   public String getProtocol() {
      for (Connector c : getServer().getConnectors())
         if (c instanceof ServerConnector) 
            for (ConnectionFactory cf : ((ServerConnector)c).getConnectionFactories())
               if (cf instanceof SslConnectionFactory)
                  return "https";
      return "http";
   }

   /**
    * Returns the hostname of this microservice.
    * <p>
    * Simply uses <code>InetAddress.getLocalHost().getHostName()</code>.
    * 
    * @return The hostname of this microservice.
    */
   public String getHostName() {
      String hostname = "localhost";
      try {
         hostname = InetAddress.getLocalHost().getHostName();
      } catch (UnknownHostException e) {}
      return hostname;
   }
   
   /**
    * Returns the URI where this microservice is listening on.
    * 
    * @return The URI where this microservice is listening on.
    */
   public URI getURI() {
      String cp = getContextPath(); 
      try {
         return new URI(getProtocol(), null, getHostName(), getPort(), "/".equals(cp) ? null : cp, null, null);
      } catch (URISyntaxException e) {
         throw new RuntimeException(e);
      }
   }

   /**
    * Method used to create (but not start) an instance of a Jetty server.
    * 
    * <p>
    * Subclasses can override this method to customize the Jetty server before it is started.
    * 
    * <p>
    * The default implementation is configured by the following values in the config file 
    * if a jetty.xml is not specified via a <code>REST/jettyXml</code> setting:
    * <p class='bcode'>
    *    <cc>#================================================================================
    *    # Jetty settings
    *    #================================================================================</cc>
    *    <cs>[Jetty]</cs>
    *    
    *    <cc># Path of the jetty.xml file used to configure the Jetty server.</cc>
    *    <ck>config</ck> = jetty.xml
    *    
    *    <cc># Resolve Juneau variables in the jetty.xml file.</cc>
    *    <ck>resolveVars</ck> = true
    *    
    *    <cc># Port to use for the jetty server.
    *    # You can specify multiple ports.  The first available will be used.  '0' indicates to try a random port.
    *    # The resulting available port gets set as the system property "availablePort" which can be referenced in the 
    *    # jetty.xml file as "$S{availablePort}" (assuming resolveVars is enabled).</cc>
    *    <ck>port</ck> = 10000,0,0,0
    * </p>
    * 
    * @return The newly-created server.
    * @throws Exception
    */
   protected Server createServer() throws Exception {
      onCreateServer();

      Config cf = getConfig();
      ObjectMap mf = getManifest();
      VarResolver vr = getVarResolver();
      
      int[] ports = cf.getObjectWithDefault("Jetty/port", mf.getWithDefault("Jetty-Port", new int[]{8000}, int[].class), int[].class);
      int availablePort = findOpenPort(ports);
      System.setProperty("availablePort", String.valueOf(availablePort));
      
      if (jettyXml == null)
         jettyXml = cf.getString("Jetty/config", mf.getString("Jetty-Config", null));
      
      if (jettyXml == null)
         throw new FormattedRuntimeException("Jetty.xml file location was not specified in the configuration file (Jetty/config) or manifest file (Jetty-Config).");
      
      String xmlConfig = null;
      
      if (jettyXml instanceof String) 
         jettyXml = new File(jettyXml.toString());
      
      if (jettyXml instanceof File) {
         File f = (File)jettyXml;
         if (f.exists())
            xmlConfig = IOUtils.read((File)jettyXml);
         else 
            throw new FormattedRuntimeException("Jetty.xml file ''{0}'' was specified but not found on the file system.", f.getName());
      } else {
         xmlConfig = IOUtils.read(jettyXml);
      }
      
      if (cf.getBoolean("Jetty/resolveVars", false))
         xmlConfig = vr.resolve(xmlConfig);
      
      getLogger().info(xmlConfig);
      
      XmlConfiguration config = new XmlConfiguration(new ByteArrayInputStream(xmlConfig.getBytes()));
      server = (Server)config.configure();
      
      return server;
   }
   
   /**
    * Adds an arbitrary servlet to this microservice.
    * 
    * @param servlet The servlet instance.
    * @param pathSpec The context path of the servlet.
    * @return This object (for method chaining).
    * @throws RuntimeException if {@link #createServer()} has not previously been called.
    */
   public RestMicroservice addServlet(Servlet servlet, String pathSpec) {
      for (Handler h : getServer().getHandlers()) {
         if (h instanceof ServletContextHandler) {
            ServletHolder sh = new ServletHolder(servlet);
            ((ServletContextHandler)h).addServlet(sh, pathSpec);
            return this;
         }
      }
      throw new RuntimeException("Servlet context handler not found in jetty server.");
   }
   
   /**
    * Adds a servlet attribute to the Jetty server.
    * 
    * @param name The server attribute name.
    * @param value The context path of the servlet.
    * @return This object (for method chaining).
    * @throws RuntimeException if {@link #createServer()} has not previously been called.
    */
   public RestMicroservice addServletAttribute(String name, Object value) {
      getServer().setAttribute(name, value);
      return this;
   }
   
   /**
    * Returns the underlying Jetty server.
    * 
    * @return The underlying Jetty server, or <jk>null</jk> if {@link #createServer()} has not yet been called.
    */
   public Server getServer() {
      if (server == null)
         throw new RuntimeException("Server not found.  createServer() must be called first.");
      return server;
   }
   
   private static int findOpenPort(int[] ports) {
      for (int port : ports) {
         // If port is 0, try a random port between ports[0] and 32767.
         if (port == 0)
            port = new Random().nextInt(32767 - ports[0] + 1) + ports[0];
         try (ServerSocket ss = new ServerSocket(port)) {
            return port;
         } catch (IOException e) {}
      }
      return 0;
   }

   /**
    * Method used to start the Jetty server created by {@link #createServer()}.
    * 
    * <p>
    * Subclasses can override this method to customize server startup.
    * 
    * @return The port that this server started on.
    * @throws Exception
    */
   protected int startServer() throws Exception {
      onStartServer();
      server.start();
      out(mb, "ServerStarted", getPort());
      onPostStartServer();
      return getPort();
   }

   /**
    * Called when {@link Config#commit()} is called on the config file.
    * 
    * <p>
    * The default behavior is configured by the following value in the config file:
    * <p class='bcode'>
    *    <cc># What to do when the config file is saved.
    *    # Possible values:
    *    #  NOTHING - Don't do anything. (default)
    *    #  RESTART_SERVER - Restart the Jetty server.
    *    #  RESTART_SERVICE - Shutdown and exit with code '3'.</cc>
    *    <ck>saveConfigAction</ck> = RESTART_SERVER
    * </p>
    */
   @Override /* Microservice */
   public void onConfigChange(List<ConfigEvent> events) {
      try {
         String saveConfigAction = getConfig().getString("saveConfigAction", "NOTHING");
         if (saveConfigAction.equals("RESTART_SERVER")) {
            new Thread() {
               @Override /* Thread */
               public void run() {
                  try {
                     RestMicroservice.this.stop();
                     RestMicroservice.this.start();
                  } catch (Exception e) {
                     getLogger().log(Level.SEVERE, e.getLocalizedMessage(), e);
                  }
               }
            }.start();
         } else if (saveConfigAction.equals("RESTART_SERVICE")) {
            stop();
            System.exit(3);
         }
      } catch (Exception e) {
         throw new RuntimeException(e);
      }
   }

   /**
    * Sets the <code>jetty.xml</code> used to configure the Jetty server.
    * 
    * <p>
    * 
    * @param jettyXml 
    *    The <code>jetty.xml</code>.
    *    <br>Can be any of the following:
    *    <ul>
    *       <li>A {@link File} representing the location on the file system.
    *       <li>An {@link InputStream} containing the contents of the file.
    *       <li>A {@link String} representing the file system path.
    *    </ul>
    * @return This object (for method chaining).
    */
   public RestMicroservice setJettyXml(Object jettyXml) {
      if (jettyXml instanceof String || jettyXml instanceof File || jettyXml instanceof InputStream || jettyXml instanceof Reader)
         this.jettyXml = jettyXml;
      else
         throw new FormattedRuntimeException("Invalid object type passed to setJettyXml()", jettyXml == null ? null : jettyXml.getClass().getName());
      return this;
   }

   
   //--------------------------------------------------------------------------------
   // Lifecycle listener methods.
   //--------------------------------------------------------------------------------

   /**
    * Called before {@link #createServer()} is called.
    * 
    * <p>
    * Subclasses can override this method to hook into the lifecycle of this application.
    */
   protected void onCreateServer() {}

   /**
    * Called before {@link #startServer()} is called.
    * 
    * <p>
    * Subclasses can override this method to hook into the lifecycle of this application.
    */
   protected void onStartServer() {}

   /**
    * Called after the Jetty server is started.
    * 
    * <p>
    * Subclasses can override this method to hook into the lifecycle of this application.
    */
   protected void onPostStartServer() {}

   /**
    * Called before the Jetty server is stopped.
    * 
    * <p>
    * Subclasses can override this method to hook into the lifecycle of this application.
    */
   protected void onStopServer() {}

   /**
    * Called after the Jetty server is stopped.
    * 
    * <p>
    * Subclasses can override this method to hook into the lifecycle of this application.
    */
   protected void onPostStopServer() {}


   //--------------------------------------------------------------------------------
   // Overridden methods.
   //--------------------------------------------------------------------------------

   @Override /* Microservice */
   public RestMicroservice setConfig(String cfPath, boolean create) throws IOException {
      super.setConfig(cfPath, create);
      return this;
   }

   @Override /* Microservice */
   public RestMicroservice setManifestContents(String...contents) throws IOException {
      super.setManifestContents(contents);
      return this;
   }
}