/**
 * 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;

import java.util.concurrent.TimeUnit;

/**
 * A <i>no-op</i> {@code StatsLogger}.
 *
 * <p>Metrics are not recorded, making this receiver useful in unit tests and as defaults in
 * situations where metrics are not strictly required.
 */
public class NullStatsLogger implements StatsLogger {

    public static final NullStatsLogger INSTANCE = new NullStatsLogger();

    /**
     * A <i>no-op</i> {@code OpStatsLogger}.
     */
    static class NullOpStatsLogger implements OpStatsLogger {
        final OpStatsData nullOpStats = new OpStatsData(0, 0, 0, new long[6]);

        @Override
        public void registerFailedEvent(long eventLatency, TimeUnit unit) {
            // nop
        }

        @Override
        public void registerSuccessfulEvent(long eventLatency, TimeUnit unit) {
            // nop
        }

        @Override
        public void registerSuccessfulValue(long value) {
            // nop
        }

        @Override
        public void registerFailedValue(long value) {
            // nop
        }

        @Override
        public OpStatsData toOpStatsData() {
            return nullOpStats;
        }

        @Override
        public void clear() {
            // nop
        }
    }
    static NullOpStatsLogger nullOpStatsLogger = new NullOpStatsLogger();

    /**
     * A <i>no-op</i> {@code Counter}.
     */
    static class NullCounter implements Counter {
        @Override
        public void clear() {
            // nop
        }

        @Override
        public void inc() {
            // nop
        }

        @Override
        public void dec() {
            // nop
        }

        @Override
        public void add(long delta) {
            // nop
        }

        @Override
        public Long get() {
            return 0L;
        }
    }
    static NullCounter nullCounter = new NullCounter();

    @Override
    public OpStatsLogger getOpStatsLogger(String name) {
        return nullOpStatsLogger;
    }

    @Override
    public Counter getCounter(String name) {
        return nullCounter;
    }

    @Override
    public <T extends Number> void registerGauge(String name, Gauge<T> gauge) {
        // nop
    }

    @Override
    public <T extends Number> void unregisterGauge(String name, Gauge<T> gauge) {
        // nop
    }

    @Override
    public StatsLogger scope(String name) {
        return this;
    }

    @Override
    public void removeScope(String name, StatsLogger statsLogger) {
        // nop
    }
}