xref: /packages/services/Car/car-lib/src/com/android/car/internal/CarRatedFloatListeners.java

/*
 * Copyright (C) 2018 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.car.internal;

import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * Represent listeners for a property grouped by their rate.
 * T is a type of EventListener such as CarPropertyEventListener
 * in {@link android.car.hardware.property.CarPropertyManager}
 * @param <T>
 * @hide
 */
public class CarRatedFloatListeners<T> {
    private final Map<T, Float> mListenersToRate = new HashMap<>(4);

    private float mUpdateRate;

    protected long mLastUpdateTime = -1;

    protected CarRatedFloatListeners(float rate) {
        mUpdateRate = rate;
    }

    /** Check listener */
    public boolean contains(T listener) {
        return mListenersToRate.containsKey(listener);
    }
    /** Return current rate after updating */
    public float getRate() {
        return mUpdateRate;
    }

    /**
     * Remove given listener from the list and update rate if necessary.
     *
     * @param listener
     * @return true if rate was updated. Otherwise, returns false.
     */
    public boolean remove(T listener) {
        mListenersToRate.remove(listener);
        if (mListenersToRate.isEmpty()) {
            return false;
        }
        Float updateRate = Collections.max(mListenersToRate.values());
        if (updateRate != mUpdateRate) {
            mUpdateRate = updateRate;
            return true;
        }
        return false;
    }

    public boolean isEmpty() {
        return mListenersToRate.isEmpty();
    }

    /**
     * Add given listener to the list and update rate if necessary.
     *
     * @param listener if null, add part is skipped.
     * @param updateRate
     * @return true if rate was updated. Otherwise, returns false.
     */
    public boolean addAndUpdateRate(T listener, float updateRate) {
        Float oldUpdateRate = mListenersToRate.put(listener, updateRate);
        if (mUpdateRate < updateRate) {
            mUpdateRate = updateRate;
            return true;
        } else if (oldUpdateRate != null && oldUpdateRate == mUpdateRate) {
            mUpdateRate = Collections.max(mListenersToRate.values());
        }
        return false;
    }

    public Collection<T> getListeners() {
        return mListenersToRate.keySet();
    }
}