/*
 * Copyright (c) 2011 Google Inc.
 *
 * Licensed 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.
 */

import org.mortbay.jetty.Connector;
import org.mortbay.jetty.Request;
import org.mortbay.jetty.Server;
import org.mortbay.jetty.handler.AbstractHandler;

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

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

/**
 * Runs a Jetty server on a free port, waiting for OAuth to redirect to it with the verification
 * code.
 * <p>
 * Mostly copied from oacurl by phopkins@google.com.
 * </p>
 *
 * @author Yaniv Inbar
 */
public final class LocalServerReceiver implements VerificationCodeReceiver {

  private static final String CALLBACK_PATH = "/Callback";

  /** Server or {@code null} before {@link #getRedirectUri()}. */
  private Server server;

  /** Verification code or {@code null} before received. */
  volatile String code;

  @Override
  public String getRedirectUri() throws Exception {
    int port = getUnusedPort();
    server = new Server(port);
    for (Connector c : server.getConnectors()) {
      c.setHost("localhost");
    }
    server.addHandler(new CallbackHandler());
    server.start();
    return "http://localhost:" + port + CALLBACK_PATH;
  }

  @Override
  public synchronized String waitForCode() {
    try {
      this.wait();
    } catch (InterruptedException exception) {
      // should not happen
    }
    return code;
  }

  @Override
  public void stop() throws Exception {
    if (server != null) {
      server.stop();
      server = null;
    }
  }

  private static int getUnusedPort() throws IOException {
    Socket s = new Socket();
    s.bind(null);
    try {
      return s.getLocalPort();
    } finally {
      s.close();
    }
  }

  /**
   * Jetty handler that takes the verifier token passed over from the OAuth provider and stashes it
   * where {@link #waitForCode} will find it.
   */
  class CallbackHandler extends AbstractHandler {

    @Override
    public void handle(
        String target, HttpServletRequest request, HttpServletResponse response, int dispatch)
        throws IOException {
      if (!CALLBACK_PATH.equals(target)) {
        return;
      }
      writeLandingHtml(response);
      response.flushBuffer();
      ((Request) request).setHandled(true);
      String error = request.getParameter("error");
      if (error != null) {
        System.out.println("Authorization failed. Error=" + error);
        System.out.println("Quitting.");
        System.exit(1);
      }
      code = request.getParameter("code");
      synchronized (LocalServerReceiver.this) {
        LocalServerReceiver.this.notify();
      }
    }

    private void writeLandingHtml(HttpServletResponse response) throws IOException {
      response.setStatus(HttpServletResponse.SC_OK);
      response.setContentType("text/html");

      PrintWriter doc = response.getWriter();
      doc.println("<html>");
      doc.println("<head><title>OAuth 2.0 Authentication Token Recieved</title></head>");
      doc.println("<body>");
      doc.println("Received verification code. Closing...");
      doc.println("<script type='text/javascript'>");
      // We open "" in the same window to trigger JS ownership of it, which lets
      // us then close it via JS, at least in Chrome.
      doc.println("window.setTimeout(function() {");
      doc.println("    window.open('', '_self', ''); window.close(); }, 1000);");
      doc.println("if (window.opener) { window.opener.checkToken(); }");
      doc.println("</script>");
      doc.println("</body>");
      doc.println("</HTML>");
      doc.flush();
    }
  }
}