/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * 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 com.android.tv.analytics;

import android.os.SystemClock;

/**
 * Times a duration.
 */
public final class DurationTimer {
    public static final long TIME_NOT_SET = -1;

    private long startTimeMs = TIME_NOT_SET;

    /**
     * Returns true if the timer is running.
     */
    public boolean isRunning() {
        return startTimeMs != TIME_NOT_SET;
    }

    /**
     * Start the timer.
     */
    public void start() {
        startTimeMs = SystemClock.elapsedRealtime();
    }

    /**
     * Returns the current duration in milliseconds or {@link #TIME_NOT_SET} if the timer is not
     * running.
     */
    public long getDuration() {
        return isRunning() ? SystemClock.elapsedRealtime() - startTimeMs : TIME_NOT_SET;
    }

    /**
     * Stops the timer and resets its value to {@link #TIME_NOT_SET}.
     *
     * @return the current duration in milliseconds or {@link #TIME_NOT_SET} if the timer is not
     * running.
     */
    public long reset() {
        long duration = getDuration();
        startTimeMs = TIME_NOT_SET;
        return duration;
    }
}