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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.util.VisibleForTesting;
import com.netflix.servo.annotations.DataSourceType;
import com.netflix.servo.util.Clock;
import com.netflix.servo.util.ClockWithOffset;

/**
 * A simple counter implementation backed by a StepLong. The value returned is a rate for the
 * previous interval as defined by the step.
 */
public class StepCounter extends AbstractMonitor implements Counter {

    private final StepLong count;

    /**
     * Creates a new instance of the counter.
     */
    public StepCounter(MonitorConfig config) {
        this(config, ClockWithOffset.INSTANCE);
    }

    /**
     * Creates a new instance of the counter.
     */
    @VisibleForTesting
    public StepCounter(MonitorConfig config, Clock clock) {
        // This class will reset the value so it is not a monotonically increasing value as
        // expected for type=COUNTER. This class looks like a counter to the user and a gauge to
        // the publishing pipeline receiving the value.
        super(config.withAdditionalTag(DataSourceType.NORMALIZED));
        count = new StepLong(0L, clock);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void increment() {
        count.addAndGet(1L);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void increment(long amount) {
        if (amount > 0L) {
            count.addAndGet(amount);
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Number getValue(int pollerIndex) {
        final Datapoint dp = count.poll(pollerIndex);
        final double stepSeconds = Pollers.POLLING_INTERVALS[pollerIndex] / 1000.0;
        return dp.isUnknown() ? Double.NaN : dp.getValue() / stepSeconds;
    }

    /**
     * Get the count for the last completed polling interval for the given poller index.
     */
    public long getCount(int pollerIndex) {
        return count.poll(pollerIndex).getValue();
    }

    /**
     * Get the current count for the given poller index.
     */
    @VisibleForTesting
    public long getCurrentCount(int pollerIndex) {
        return count.getCurrent(pollerIndex).get();
    }

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

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        StepCounter that = (StepCounter) o;
        return config.equals(that.config) && getCount(0) == that.getCount(0);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int hashCode() {
        return config.hashCode();
    }
}