package jalview.rest;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.BindException;

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

import jalview.httpserver.AbstractRequestHandler;

/**
 * A simple handler to process (or delegate) HTTP requests on /jalview/rest
 */
public class RestHandler extends AbstractRequestHandler
{
  private static final String MY_PATH = "rest";

  private static final String MY_NAME = "Rest";

  /**
   * Singleton instance of this class
   */
  private static RestHandler instance = null;

  /**
   * Returns the singleton instance of this class
   * 
   * @return
   * @throws BindException
   */
  public static RestHandler getInstance() throws BindException
  {
    synchronized (RestHandler.class)
    {
      if (instance == null)
      {
        instance = new RestHandler();
      }
    }
    return instance;
  }

  /**
   * Private constructor enforces use of singleton
   * 
   * @throws BindException
   */
  private RestHandler() throws BindException
  {
    setPath(MY_PATH);

    /*
     * We don't register the handler here - this is done as a special case in
     * HttpServer initialisation; to do it here would invite an infinite loop of
     * RestHandler/HttpServer constructor
     */
  }

  /**
   * Handle a jalview/rest request
   * 
   * @throws IOException
   */
  @Override
  protected void processRequest(HttpServletRequest request,
          HttpServletResponse response) throws IOException
  {
    /*
     * Currently just echoes the request; add helper classes as required to
     * process requests
     */
    final String queryString = request.getQueryString();
    final String reply = "REST not yet implemented; received "
            + request.getMethod() + ": " + request.getRequestURL()
            + (queryString == null ? "" : "?" + queryString);
    System.out.println(reply);

    response.setHeader("Cache-Control", "no-cache/no-store");
    response.setHeader("Content-type", "text/plain");
    final PrintWriter writer = response.getWriter();
    writer.write(reply);
    writer.close();
  }

  /**
   * Returns a display name for this service
   */
  @Override
  public String getName()
  {
    return MY_NAME;
  }

}