/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to you 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 org.apache.bookkeeper.stats.prometheus;

import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.LongAdder;
import org.apache.bookkeeper.stats.Counter;

/**
 * {@link Counter} implementation based on {@link LongAdder}.
 *
 * <p>LongAdder keeps a counter per-thread and then aggregates to get the result, in order to avoid contention between
 * multiple threads.
 */
public class LongAdderCounter implements Counter {
    private final LongAdder counter = new LongAdder();

    private Map<String, String> labels;

    // used for lazy registration for thread scoped metric
    private boolean threadInitialized;

    public LongAdderCounter(Map<String, String> labels) {
        this.labels = labels;
    }

    @Override
    public void clear() {
        counter.reset();
    }

    @Override
    public void inc() {
        counter.increment();
    }

    @Override
    public void dec() {
        counter.decrement();
    }

    @Override
    public void addCount(long delta) {
        counter.add(delta);
    }

    /**
     * When counter is used to count time.
     * consistent with the {@link DataSketchesOpStatsLogger#registerSuccessfulEvent(long, TimeUnit)} 's logic
     * */
    @Override
    public void addLatency(long eventLatency, TimeUnit unit) {
        long valueMillis = unit.toMillis(eventLatency);
        counter.add(valueMillis);
    }

    @Override
    public Long get() {
        return counter.sum();
    }

    public Map<String, String> getLabels() {
        return labels;
    }

    public boolean isThreadInitialized() {
        return threadInitialized;
    }

    public void initializeThread(Map<String, String> labels) {
        this.labels = labels;
        this.threadInitialized = true;
    }
}
