// Licensed to the Software Freedom Conservancy (SFC) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The SFC 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.openqa.selenium.events.zeromq;

import static java.nio.charset.StandardCharsets.UTF_8;

import com.google.common.collect.EvictingQueue;
import dev.failsafe.Failsafe;
import dev.failsafe.RetryPolicy;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.UnknownHostException;
import java.time.temporal.ChronoUnit;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Queue;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.function.Consumer;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.openqa.selenium.concurrent.ExecutorServices;
import org.openqa.selenium.events.Event;
import org.openqa.selenium.events.EventBus;
import org.openqa.selenium.events.EventListener;
import org.openqa.selenium.events.EventName;
import org.openqa.selenium.grid.security.Secret;
import org.openqa.selenium.internal.Require;
import org.openqa.selenium.json.Json;
import org.openqa.selenium.json.JsonException;
import org.openqa.selenium.json.JsonOutput;
import org.zeromq.SocketType;
import org.zeromq.ZContext;
import org.zeromq.ZMQ;

class UnboundZmqEventBus implements EventBus {

  static final EventName REJECTED_EVENT = new EventName("selenium-rejected-event");
  private static final Logger LOG = Logger.getLogger(UnboundZmqEventBus.class.getName());
  private static final Json JSON = new Json();
  private final AtomicBoolean pollingStarted = new AtomicBoolean(false);
  private final PollingRunnable socketPolling;
  private final ExecutorService socketPollingExecutor;
  private final ExecutorService socketPublishingExecutor;
  private final ExecutorService listenerNotificationExecutor;

  private final Map<EventName, List<Consumer<Event>>> listeners = new ConcurrentHashMap<>();
  private final Queue<UUID> recentMessages = EvictingQueue.create(128);
  private final String encodedSecret;
  private final ZMQ.Poller poller;

  private ZMQ.Socket pub;
  private ZMQ.Socket sub;

  UnboundZmqEventBus(
      ZContext context, String publishConnection, String subscribeConnection, Secret secret) {
    Require.nonNull("Secret", secret);
    StringBuilder builder = new StringBuilder();
    try (JsonOutput out = JSON.newOutput(builder)) {
      out.setPrettyPrint(false).writeClassName(false).write(secret);
    }
    this.encodedSecret = builder.toString();

    this.socketPollingExecutor =
        Executors.newSingleThreadExecutor(
            r -> {
              Thread thread = new Thread(r);
              thread.setName("Event Bus Poller");
              thread.setDaemon(true);
              return thread;
            });

    this.socketPublishingExecutor =
        Executors.newSingleThreadExecutor(
            r -> {
              Thread thread = new Thread(r);
              thread.setName("Event Bus Publisher");
              thread.setDaemon(true);
              return thread;
            });

    this.listenerNotificationExecutor =
        Executors.newFixedThreadPool(
            Math.max(Runtime.getRuntime().availableProcessors() / 2, 2), // At least two threads
            r -> {
              Thread thread = new Thread(r);
              thread.setName("Event Bus Listener Notifier");
              thread.setDaemon(true);
              return thread;
            });

    String connectionMessage =
        String.format("Connecting to %s and %s", publishConnection, subscribeConnection);
    LOG.info(connectionMessage);

    RetryPolicy<Object> retryPolicy =
        RetryPolicy.builder()
            .withMaxAttempts(5)
            .withDelay(5, 10, ChronoUnit.SECONDS)
            .onFailedAttempt(
                e -> LOG.log(Level.WARNING, String.format("%s failed", connectionMessage)))
            .onRetry(
                e ->
                    LOG.log(
                        Level.WARNING,
                        String.format("Failure #%s. Retrying.", e.getAttemptCount())))
            .onRetriesExceeded(e -> LOG.log(Level.WARNING, "Connection aborted."))
            .build();

    // Access to the zmq socket is safe here: no threads.
    Failsafe.with(retryPolicy)
        .run(
            () -> {
              sub = context.createSocket(SocketType.SUB);
              sub.setIPv6(isSubAddressIPv6(publishConnection));
              sub.connect(publishConnection);
              sub.subscribe(new byte[0]);

              pub = context.createSocket(SocketType.PUB);
              pub.setIPv6(isSubAddressIPv6(subscribeConnection));
              pub.connect(subscribeConnection);
            });
    // Connections are already established
    this.poller = context.createPoller(1);
    this.poller.register(Objects.requireNonNull(sub), ZMQ.Poller.POLLIN);

    LOG.info("Sockets created");

    socketPolling = new PollingRunnable(secret);
    socketPollingExecutor.submit(socketPolling);

    // Give ourselves up to a second to connect, using The World's Worst heuristic. If we don't
    // manage to connect, it's not the end of the world, as the socket we're connecting to may not
    // be up yet.
    while (!pollingStarted.get()) {
      try {
        Thread.sleep(1000);
      } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
        throw new RuntimeException(e);
      }
    }

    LOG.info("Event bus ready");
  }

  @Override
  public boolean isReady() {
    return !socketPollingExecutor.isShutdown();
  }

  private boolean isSubAddressIPv6(String connection) {
    try {
      URI uri = new URI(connection);

      if ("inproc".equals(uri.getScheme())) {
        return false;
      }

      return InetAddress.getByName(uri.getHost()) instanceof Inet6Address;
    } catch (UnknownHostException | URISyntaxException e) {
      LOG.log(
          Level.WARNING,
          String.format("Could not determine if the address %s is IPv6 or IPv4", connection),
          e);
    }
    return false;
  }

  @Override
  public void addListener(EventListener<?> listener) {
    Require.nonNull("Listener", listener);

    List<Consumer<Event>> typeListeners =
        listeners.computeIfAbsent(listener.getEventName(), t -> new LinkedList<>());
    typeListeners.add(listener);
  }

  @Override
  public void fire(Event event) {
    Require.nonNull("Event to send", event);

    socketPublishingExecutor.execute(
        () -> {
          pub.sendMore(event.getType().getName().getBytes(UTF_8));
          pub.sendMore(encodedSecret.getBytes(UTF_8));
          pub.sendMore(event.getId().toString().getBytes(UTF_8));
          pub.send(event.getRawData().getBytes(UTF_8));
        });
  }

  @Override
  public void close() {
    socketPolling.shutdown = true;
    ExecutorServices.shutdownGracefully("Event Bus Poller", socketPollingExecutor);
    ExecutorServices.shutdownGracefully("Event Bus Publisher", socketPublishingExecutor);
    ExecutorServices.shutdownGracefully(
        "Event Bus Listener Notifier", listenerNotificationExecutor);
    poller.close();

    if (sub != null) {
      sub.close();
    }
    if (pub != null) {
      pub.close();
    }
  }

  private class PollingRunnable implements Runnable {
    private final Secret secret;
    private volatile boolean shutdown;

    public PollingRunnable(Secret secret) {
      this.secret = secret;
    }

    @Override
    public void run() {
      while (!Thread.currentThread().isInterrupted() && !shutdown) {
        try {
          int count = poller.poll(150);

          pollingStarted.lazySet(true);

          for (int i = 0; i < count; i++) {
            if (poller.pollin(i)) {
              ZMQ.Socket socket = poller.getSocket(i);

              EventName eventName = new EventName(new String(socket.recv(), UTF_8));
              // Processing only events we are listening to
              if (!listeners.containsKey(eventName)) {
                continue;
              }

              Secret eventSecret;
              String receivedEventSecret = new String(socket.recv(), UTF_8);
              try {
                eventSecret = JSON.toType(receivedEventSecret, Secret.class);
              } catch (JsonException ignore) {
                rejectEvent(
                    eventName,
                    receivedEventSecret,
                    "Could not parse event secret, rejecting event.");
                continue;
              }

              UUID id;
              String eventId = new String(socket.recv(), UTF_8);
              try {
                id = UUID.fromString(eventId);
              } catch (IllegalArgumentException ignore) {
                rejectEvent(eventName, eventId, "Could not parse event id, rejecting event.");
                continue;
              }

              String data = new String(socket.recv(), UTF_8);

              // Don't bother doing more work if we've seen this message.
              if (recentMessages.contains(id)) {
                continue;
              }

              Object converted = JSON.toType(data, Object.class);
              Event event = new Event(id, eventName, converted);

              recentMessages.add(id);

              if (!Secret.matches(secret, eventSecret)) {
                rejectEvent(eventName, data, "Rejecting message without a valid secret");
                continue;
              }

              notifyListeners(eventName, event);
            }
          }
        } catch (Exception e) {
          if (!(e.getCause() instanceof AssertionError)) {
            LOG.log(
                Level.WARNING,
                e,
                () -> "Caught exception while polling for event bus messages: " + e.getMessage());
          }
        }
      }
    }

    private void rejectEvent(EventName eventName, String data, String message) {
      Event rejectedEvent =
          new Event(REJECTED_EVENT, new ZeroMqEventBus.RejectedEvent(eventName, data));
      LOG.log(Level.SEVERE, "{0}. {1}", new Object[] {message, rejectedEvent});

      notifyListeners(REJECTED_EVENT, rejectedEvent);
    }

    private void notifyListeners(EventName eventName, Event event) {
      List<Consumer<Event>> eventListeners = listeners.getOrDefault(eventName, new ArrayList<>());
      eventListeners.forEach(
          listener ->
              listenerNotificationExecutor.submit(
                  () -> {
                    try {
                      listener.accept(event);
                    } catch (Exception e) {
                      LOG.log(
                          Level.WARNING, e, () -> "Caught exception from listener: " + listener);
                    }
                  }));
    }
  }
}
