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/*
 * Copyright 2015 The gRPC Authors
 *
 * 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.
 */

package io.grpc.netty;

import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedExceptionAction;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLEngine;

/**
 * Utility class for determining support for Jetty TLS ALPN/NPN.
 */
final class JettyTlsUtil {
  private JettyTlsUtil() {
  }

  private static Throwable jettyAlpnUnavailabilityCause;
  private static Throwable jettyNpnUnavailabilityCause;

  private static class Java9AlpnUnavailabilityCauseHolder {

    static final Throwable cause = checkAlpnAvailability();

    static Throwable checkAlpnAvailability() {
      try {
        SSLContext context = SSLContext.getInstance("TLS");
        context.init(null, null, null);
        SSLEngine engine = context.createSSLEngine();
        Method getApplicationProtocol =
            AccessController.doPrivileged(new PrivilegedExceptionAction() {
              @Override
              public Method run() throws Exception {
                return SSLEngine.class.getMethod("getApplicationProtocol");
              }
            });
        getApplicationProtocol.invoke(engine);
        return null;
      } catch (Throwable t) {
        return t;
      }
    }
  }

  /**
   * Indicates whether or not the Jetty ALPN jar is installed in the boot classloader.
   */
  static synchronized boolean isJettyAlpnConfigured() {
    try {
      Class.forName("org.eclipse.jetty.alpn.ALPN", true, null);
      return true;
    } catch (ClassNotFoundException e) {
      jettyAlpnUnavailabilityCause = e;
      return false;
    }
  }

  static synchronized Throwable getJettyAlpnUnavailabilityCause() {
    // This case should be unlikely
    if (jettyAlpnUnavailabilityCause == null) {
      @SuppressWarnings("UnusedVariable")
      boolean discard = isJettyAlpnConfigured();
    }
    return jettyAlpnUnavailabilityCause;
  }

  /**
   * Indicates whether or not the Jetty NPN jar is installed in the boot classloader.
   */
  static synchronized boolean isJettyNpnConfigured() {
    try {
      Class.forName("org.eclipse.jetty.npn.NextProtoNego", true, null);
      return true;
    } catch (ClassNotFoundException e) {
      jettyNpnUnavailabilityCause = e;
      return false;
    }
  }

  static synchronized Throwable getJettyNpnUnavailabilityCause() {
    // This case should be unlikely
    if (jettyNpnUnavailabilityCause == null) {
      @SuppressWarnings("UnusedVariable")
      boolean discard = isJettyNpnConfigured();
    }
    return jettyNpnUnavailabilityCause;
  }

  /**
   * Indicates whether Java 9 ALPN is available.
   */
  static boolean isJava9AlpnAvailable() {
    return getJava9AlpnUnavailabilityCause() == null;
  }

  static Throwable getJava9AlpnUnavailabilityCause() {
    return Java9AlpnUnavailabilityCauseHolder.cause;
  }
}