/*
 * Copyright (C) 2022 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.quicksearchbox

import android.os.SystemClock

/**
 * Tracks latency in wall-clock time. Since [.getLatency] returns an `int`, latencies over 2^31 ms
 * (~ 25 days) cannot be measured. This class uses [SystemClock.uptimeMillis] which does not advance
 * during deep sleep.
 */
class LatencyTracker {
  /** Start time, in milliseconds as returned by [SystemClock.uptimeMillis]. */
  private var mStartTime: Long

  /** Resets the start time. */
  fun reset() {
    mStartTime = SystemClock.uptimeMillis()
  }

  /** Gets the number of milliseconds since the object was created, or [.reset] was called. */
  val latency: Int
    get() {
      val now: Long = SystemClock.uptimeMillis()
      return (now - mStartTime).toInt()
    }

  /** Creates a new latency tracker and sets the start time. */
  init {
    mStartTime = SystemClock.uptimeMillis()
  }
}