/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

package org.mozilla.gecko.util;

import android.os.Handler;
import android.os.Looper;
import android.util.Log;
import org.mozilla.gecko.annotation.RobocopTarget;

public final class ThreadUtils {
  private static final String LOGTAG = "ThreadUtils";

  /**
   * Controls the action taken when a method like {@link
   * ThreadUtils#assertOnUiThread(AssertBehavior)} detects a problem.
   */
  public enum AssertBehavior {
    NONE,
    THROW,
  }

  private static final Thread sUiThread = Looper.getMainLooper().getThread();
  private static final Handler sUiHandler = new Handler(Looper.getMainLooper());

  // Referenced directly from GeckoAppShell in highly performance-sensitive code (The extra
  // function call of the getter was harming performance. (Bug 897123))
  // Once Bug 709230 is resolved we should reconsider this as ProGuard should be able to optimise
  // this out at compile time.
  public static Handler sGeckoHandler;
  public static volatile Thread sGeckoThread;

  public static Thread getUiThread() {
    return sUiThread;
  }

  public static Handler getUiHandler() {
    return sUiHandler;
  }

  /**
   * Runs the provided runnable on the UI thread. If this method is called on the UI thread the
   * runnable will be executed synchronously.
   *
   * @param runnable the runnable to be executed.
   */
  public static void runOnUiThread(final Runnable runnable) {
    // We're on the UI thread already, let's just run this
    if (isOnUiThread()) {
      runnable.run();
      return;
    }

    postToUiThread(runnable);
  }

  public static void postToUiThread(final Runnable runnable) {
    sUiHandler.post(runnable);
  }

  public static void postToUiThreadDelayed(final Runnable runnable, final long delayMillis) {
    sUiHandler.postDelayed(runnable, delayMillis);
  }

  public static void removeUiThreadCallbacks(final Runnable runnable) {
    sUiHandler.removeCallbacks(runnable);
  }

  public static Handler getBackgroundHandler() {
    return GeckoBackgroundThread.getHandler();
  }

  public static void postToBackgroundThread(final Runnable runnable) {
    GeckoBackgroundThread.post(runnable);
  }

  public static void assertOnUiThread(final AssertBehavior assertBehavior) {
    assertOnThread(getUiThread(), assertBehavior);
  }

  public static void assertOnUiThread() {
    assertOnThread(getUiThread(), AssertBehavior.THROW);
  }

  @RobocopTarget
  public static void assertOnGeckoThread() {
    assertOnThread(sGeckoThread, AssertBehavior.THROW);
  }

  public static void assertOnThread(final Thread expectedThread, final AssertBehavior behavior) {
    assertOnThreadComparison(expectedThread, behavior, true);
  }

  private static void assertOnThreadComparison(
      final Thread expectedThread, final AssertBehavior behavior, final boolean expected) {
    final Thread currentThread = Thread.currentThread();
    final long currentThreadId = currentThread.getId();
    final long expectedThreadId = expectedThread.getId();

    if ((currentThreadId == expectedThreadId) == expected) {
      return;
    }

    final String message;
    if (expected) {
      message =
          "Expected thread "
              + expectedThreadId
              + " (\""
              + expectedThread.getName()
              + "\"), but running on thread "
              + currentThreadId
              + " (\""
              + currentThread.getName()
              + "\")";
    } else {
      message =
          "Expected anything but "
              + expectedThreadId
              + " (\""
              + expectedThread.getName()
              + "\"), but running there.";
    }

    final IllegalThreadStateException e = new IllegalThreadStateException(message);

    switch (behavior) {
      case THROW:
        throw e;
      default:
        Log.e(LOGTAG, "Method called on wrong thread!", e);
    }
  }

  public static boolean isOnUiThread() {
    return isOnThread(getUiThread());
  }

  @RobocopTarget
  public static boolean isOnThread(final Thread thread) {
    return (Thread.currentThread().getId() == thread.getId());
  }
}