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/**
 * Copyright 2013 Netflix, Inc.
 *
 * 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.netflix.servo.monitor;

import com.netflix.servo.annotations.DataSourceType;

import java.util.concurrent.atomic.AtomicLong;

/**
 * A simple counter implementation backed by an {@link java.util.concurrent.atomic.AtomicLong}.
 * The value is the total count for the life of the counter. Observers are responsible
 * for converting to a rate and handling overflows if they occur.
 */
public final class BasicCounter extends AbstractMonitor implements Counter {
    private final AtomicLong count = new AtomicLong();

    /**
     * Creates a new instance of the counter.
     */
    public BasicCounter(MonitorConfig config) {
        super(config.withAdditionalTag(DataSourceType.COUNTER));
    }

    /** {@inheritDoc} */
    @Override
    public void increment() {
        count.incrementAndGet();
    }

    /** {@inheritDoc} */
    @Override
    public void increment(long amount) {
        count.getAndAdd(amount);
    }

    /** {@inheritDoc} */
    @Override
    public Number getValue(int pollerIdx) {
        return count.get();
    }

    /** {@inheritDoc} */
    @Override
    public boolean equals(Object obj) {
        if (obj == null || !(obj instanceof BasicCounter)) {
            return false;
        }
        BasicCounter m = (BasicCounter) obj;
        return config.equals(m.getConfig()) && count.get() == m.count.get();
    }

    /** {@inheritDoc} */
    @Override
    public int hashCode() {
        int result = config.hashCode();
        long n = count.get();
        result = 31 * result +  (int) (n ^ (n >>> 32));
        return result;
    }

    /** {@inheritDoc} */
    @Override
    public String toString() {
        return "BasicCounter{config=" + config + ", count=" + count.get() + '}';
    }
}