/**
 * 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.hadoop.mapred;

import java.io.*;
import java.net.URL;
import java.net.URLDecoder;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.util.*;
import org.mortbay.http.HttpContext;
import org.mortbay.http.handler.ResourceHandler;
import org.mortbay.http.SocketListener;
import org.mortbay.jetty.servlet.WebApplicationContext;

/**
 * Create a Jetty embedded server to answer http requests. The primary goal
 * is to serve up status information for the server.
 * There are three contexts:
 *   "/logs/" -> points to the log directory
 *   "/static/" -> points to common static files (src/webapps/static)
 *   "/" -> the jsp server code from (src/webapps/<name>)
 * @author Owen O'Malley
 */
public class StatusHttpServer {
  private static final boolean isWindows = 
    System.getProperty("os.name").startsWith("Windows");
  private org.mortbay.jetty.Server webServer;
  private SocketListener listener;
  private boolean findPort;
  private WebApplicationContext webAppContext;
  private static final Log LOG =
    LogFactory.getLog(StatusHttpServer.class.getName());
  
  /**
   * Create a status server on the given port.
   * The jsp scripts are taken from src/webapps/<name>.
   * @param name The name of the server
   * @param port The port to use on the server
   * @param findPort whether the server should start at the given port and 
   *        increment by 1 until it finds a free port.
   */
  public StatusHttpServer(String name, String bindAddress, int port, 
                          boolean findPort) throws IOException {
    webServer = new org.mortbay.jetty.Server();
    this.findPort = findPort;
    listener = new SocketListener();
    listener.setPort(port);
    listener.setHost(bindAddress);
    webServer.addListener(listener);

    // set up the context for "/logs/" if "hadoop.log.dir" property is defined. 
    String logDir = System.getProperty("hadoop.log.dir");
    if (logDir != null) {
      HttpContext logContext = new HttpContext();
      logContext.setContextPath("/logs/*");
      logContext.setResourceBase(logDir);
      logContext.addHandler(new ResourceHandler());
      webServer.addContext(logContext);
    }

    // set up the context for "/static/*"
    String appDir = getWebAppsPath();
    HttpContext staticContext = new HttpContext();
    staticContext.setContextPath("/static/*");
    staticContext.setResourceBase(appDir + "/static");
    staticContext.addHandler(new ResourceHandler());
    webServer.addContext(staticContext);

    // set up the context for "/" jsp files
    webAppContext = 
      webServer.addWebApplication("/", appDir + File.separator + name);
    addServlet("stacks", "/stacks", StackServlet.class);
  }

  /**
   * Set a value in the webapp context. These values are available to the jsp
   * pages as "application.getAttribute(name)".
   * @param name The name of the attribute
   * @param value The value of the attribute
   */
  public void setAttribute(String name, Object value) {
    webAppContext.setAttribute(name, value);
  }

  /**
   * Add a servlet in the server.
   * @param name The name of the servlet (can be passed as null)
   * @param pathSpec The path spec for the servlet
   * @param servletClass The servlet class
   */
  public <T extends HttpServlet> 
                    void addServlet(String name, String pathSpec, 
                                    Class<T> servletClass) {
    WebApplicationContext context = webAppContext;
    try {
      if (name == null) {
        context.addServlet(pathSpec, servletClass.getName());
      } else {
        context.addServlet(name, pathSpec, servletClass.getName());
      } 
    } catch (ClassNotFoundException ex) {
      throw makeRuntimeException("Problem instantiating class", ex);
    } catch (InstantiationException ex) {
      throw makeRuntimeException("Problem instantiating class", ex);
    } catch (IllegalAccessException ex) {
      throw makeRuntimeException("Problem instantiating class", ex);
    }
  }
  
  private static RuntimeException makeRuntimeException(String msg, 
                                                       Throwable cause) {
    RuntimeException result = new RuntimeException(msg);
    if (cause != null) {
      result.initCause(cause);
    }
    return result;
  }
  
  /**
   * Get the value in the webapp context.
   * @param name The name of the attribute
   * @return The value of the attribute
   */
  public Object getAttribute(String name) {
    return webAppContext.getAttribute(name);
  }
  
  /**
   * Get the pathname to the webapps files.
   * @return the pathname as a URL
   */
  private static String getWebAppsPath() throws IOException {
    URL url = StatusHttpServer.class.getClassLoader().getResource("webapps");
    if (url == null) 
      throw new IOException("webapps not found in CLASSPATH"); 
    return url.toString();
  }
  
  /**
   * Get the port that the server is on
   * @return the port
   */
  public int getPort() {
    return listener.getPort();
  }

  public void setThreads(int min, int max) {
    listener.setMinThreads(min);
    listener.setMaxThreads(max);
  }
  /**
   * Start the server. Does not wait for the server to start.
   */
  public void start() throws IOException {
    try {
      while (true) {
        try {
          webServer.start();
          break;
        } catch (org.mortbay.util.MultiException ex) {
          // look for the multi exception containing a bind exception,
          // in that case try the next port number.
          boolean needNewPort = false;
          for(int i=0; i < ex.size(); ++i) {
            Exception sub = ex.getException(i);
            if (sub instanceof java.net.BindException) {
              needNewPort = true;
              break;
            }
          }
          if (!findPort || !needNewPort) {
            throw ex;
          } else {
            listener.setPort(listener.getPort() + 1);
          }
        }
      }
    } catch (IOException ie) {
      throw ie;
    } catch (Exception e) {
      IOException ie = new IOException("Problem starting http server");
      ie.initCause(e);
      throw ie;
    }
  }
  
  /**
   * stop the server
   */
  public void stop() throws InterruptedException {
    webServer.stop();
  }
  
  /**
   * A very simple servlet to serve up a text representation of the current
   * stack traces. It both returns the stacks to the caller and logs them.
   * Currently the stack traces are done sequentially rather than exactly the
   * same data.
   * @author Owen O'Malley
   */
  public static class StackServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, 
                      HttpServletResponse response
                      ) throws ServletException, IOException {
      OutputStream outStream = response.getOutputStream();
      ReflectionUtils.printThreadInfo(new PrintWriter(outStream), "");
      outStream.close();
      ReflectionUtils.logThreadInfo(LOG, "jsp requested", 1);      
    }
  }

}
