/* -*- 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;

import android.os.SystemClock;
import android.util.Log;
import org.mozilla.gecko.annotation.WrapForJNI;

/**
 * All telemetry times are relative to one of two clocks:
 *
 * <p>* Real time since the device was booted, including deep sleep. Use this as a substitute for
 * wall clock. * Uptime since the device was booted, excluding deep sleep. Use this to avoid timing
 * a user activity when their phone is in their pocket!
 *
 * <p>The majority of methods in this class are defined in terms of real time.
 */
public class TelemetryUtils {
  private static final String LOGTAG = "TelemetryUtils";

  @WrapForJNI(stubName = "AddHistogram", dispatchTo = "gecko")
  private static native void nativeAddHistogram(String name, int value);

  public static long uptime() {
    return SystemClock.uptimeMillis();
  }

  public static long realtime() {
    return SystemClock.elapsedRealtime();
  }

  // Define new histograms in:
  // toolkit/components/telemetry/Histograms.json
  public static void addToHistogram(final String name, final int value) {
    if (GeckoThread.isRunning()) {
      nativeAddHistogram(name, value);
    } else {
      GeckoThread.queueNativeCall(
          TelemetryUtils.class, "nativeAddHistogram", String.class, name, value);
    }
  }

  public abstract static class Timer {
    private final long mStartTime;
    private final String mName;

    private volatile boolean mHasFinished;
    private volatile long mElapsed = -1;

    protected abstract long now();

    public Timer(final String name) {
      mName = name;
      mStartTime = now();
    }

    public void cancel() {
      mHasFinished = true;
    }

    public long getElapsed() {
      return mElapsed;
    }

    public void stop() {
      // Only the first stop counts.
      if (mHasFinished) {
        return;
      }

      mHasFinished = true;

      final long elapsed = now() - mStartTime;
      if (elapsed < 0) {
        Log.e(LOGTAG, "Current time less than start time -- clock shenanigans?");
        return;
      }

      mElapsed = elapsed;
      if (elapsed > Integer.MAX_VALUE) {
        Log.e(LOGTAG, "Duration of " + elapsed + "ms is too great to add to histogram.");
        return;
      }

      addToHistogram(mName, (int) (elapsed));
    }
  }

  public static class UptimeTimer extends Timer {
    public UptimeTimer(final String name) {
      super(name);
    }

    @Override
    protected long now() {
      return TelemetryUtils.uptime();
    }
  }
}