content: /*
   * Copyright (C) 2019 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.server.wifi.util;
  
  import com.android.server.wifi.Clock;
  
  /**
   * Manages a quota that is reset at the beginning of each new time period.
   */
  public class TimedQuotaManager {
      private final Clock mClock;
  
      private final long mQuota;
      private final long mPeriodMillis;
      private final long mStartTimeMillis;
  
      /**
       * The number of elapsed periods between {@link #mStartTimeMillis} and the time of the last call
       * to {@link #requestQuota()}.
       */
      private long mLastPeriod;
      /** How much quota has been consumed in the current period. */
      private long mConsumedQuota;
  
      /**
       * Constructor.
       * @param clock Clock instance.
       * @param quota the maximum quota for a given period.
       * @param periodMillis the quota will be reset at the beginning of each new period.
       */
      public TimedQuotaManager(Clock clock, long quota, long periodMillis) {
          mClock = clock;
          mQuota = quota;
          mPeriodMillis = periodMillis;
          mStartTimeMillis = clock.getElapsedSinceBootMillis();
          mLastPeriod = 0;
          mConsumedQuota = 0;
      }
  
      /**
       * Requests one quota. If there is sufficient remaining quota for the current period,
       * returns true and consumes one quota. Otherwise, returns false.
       */
      public boolean requestQuota() {
          long currentPeriod = getCurrentPeriod();
          if (mLastPeriod < currentPeriod) {
              mLastPeriod = currentPeriod;
              mConsumedQuota = 0;
          }
          if (mConsumedQuota < mQuota) {
              mConsumedQuota++;
              return true;
          }
          return false;
      }
  
      private long getCurrentPeriod() {
          return (mClock.getElapsedSinceBootMillis() - mStartTimeMillis) / mPeriodMillis;
      }
  
      @Override
      public String toString() {
          return "TimedQuotaManager{"
                  + "mQuota=" + mQuota
                  + ", mPeriodMillis=" + mPeriodMillis
                  + ", mStartTimeMillis=" + mStartTimeMillis
                  + ", mLastPeriod=" + mLastPeriod
                  + ", mConsumedQuota=" + mConsumedQuota
                  + '}';
      }
  }
  