/**
 * Copyright (C) 2011 - present by OpenGamma Inc. and the OpenGamma group of companies
 *
 * Please see distribution for license.
 */
package com.opengamma.web.analytics.push;

import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.ws.rs.core.MediaType;

import org.json.JSONException;
import org.json.JSONObject;

import com.opengamma.OpenGammaRuntimeException;
import com.opengamma.util.auth.AuthUtils;

/**
 * <p>Sets up a connection for a client.  A connection corresponds to one view, e.g. a single browser tab or
 * window.  A user can have multiple simultaneous client connections.  The client ID that identifies the
 * connection is sent in the response as JSON:</p>
 * {@code {"clientId": <clientId>}}.
 * <p>This ID must be passed to all other operations for this client.</p>
 */
public class HandshakeServlet extends HttpServlet {

  /** Serialization version. */
  private static final long serialVersionUID = 1L;
  /** Request parameter name. */
  private static final String METHOD = "method";
  /** Request parameter value. */
  private static final String GET = "GET";

  /**
   * The connection manager.
   */
  private ConnectionManager _connectionManager;

  @Override
  public void init(ServletConfig config) throws ServletException {
    super.init(config);
    _connectionManager = WebPushServletContextUtils.getConnectionManager(config.getServletContext());
  }

  //-------------------------------------------------------------------------
  // this is a hack to get round a problem with browsers caching GET requests even when they're told not to
  @Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    String method = req.getParameter(METHOD);
    if (GET.equals(method)) {
      doGet(req, resp);
    } else {
      resp.setStatus(HttpServletResponse.SC_METHOD_NOT_ALLOWED);
    }
  }

  @Override
  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    String userName = (AuthUtils.isPermissive() ? null : AuthUtils.getUserName());
    String clientId = _connectionManager.clientConnected(userName);
    resp.setContentType(MediaType.APPLICATION_JSON);
    JSONObject json = new JSONObject();
    try {
      json.put("clientId", clientId);
    } catch (JSONException e) {
      throw new OpenGammaRuntimeException("Unexpected problem creating JSON", e);
    }
    resp.getWriter().write(json.toString());
  }

}