package com.codahale.metrics;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

/**
 * A meter metric which measures mean throughput and one-, five-, and fifteen-minute
 * exponentially-weighted moving average throughputs.
 *
 * @see EWMA
 */
public class Meter implements Metered {
    private static final long TICK_INTERVAL = TimeUnit.SECONDS.toNanos(5);

    private final EWMA m1Rate = EWMA.oneMinuteEWMA();
    private final EWMA m5Rate = EWMA.fiveMinuteEWMA();
    private final EWMA m15Rate = EWMA.fifteenMinuteEWMA();

    private final LongAdder count = new LongAdder();
    private final long startTime;
    private final AtomicLong lastTick;
    private final Clock clock;

    /**
     * Creates a new {@link Meter}.
     */
    public Meter() {
        this(Clock.defaultClock());
    }

    /**
     * Creates a new {@link Meter}.
     *
     * @param clock      the clock to use for the meter ticks
     */
    public Meter(Clock clock) {
        this.clock = clock;
        this.startTime = this.clock.getTick();
        this.lastTick = new AtomicLong(startTime);
    }

    /**
     * Mark the occurrence of an event.
     */
    public void mark() {
        mark(1);
    }

    /**
     * Mark the occurrence of a given number of events.
     *
     * @param n the number of events
     */
    public void mark(long n) {
        tickIfNecessary();
        count.add(n);
        m1Rate.update(n);
        m5Rate.update(n);
        m15Rate.update(n);
    }

    private void tickIfNecessary() {
        final long oldTick = lastTick.get();
        final long newTick = clock.getTick();
        final long age = newTick - oldTick;
        if (age > TICK_INTERVAL && lastTick.compareAndSet(oldTick, newTick)) {
            final long requiredTicks = age / TICK_INTERVAL;
            for (long i = 0; i < requiredTicks; i++) {
                m1Rate.tick();
                m5Rate.tick();
                m15Rate.tick();
            }
        }
    }

    @Override
    public long getCount() {
        return count.sum();
    }

    @Override
    public double getFifteenMinuteRate() {
        tickIfNecessary();
        return m15Rate.getRate(TimeUnit.SECONDS);
    }

    @Override
    public double getFiveMinuteRate() {
        tickIfNecessary();
        return m5Rate.getRate(TimeUnit.SECONDS);
    }

    @Override
    public double getMeanRate() {
        if (getCount() == 0) {
            return 0.0;
        } else {
            final double elapsed = (clock.getTick() - startTime);
            return getCount() / elapsed * TimeUnit.SECONDS.toNanos(1);
        }
    }

    @Override
    public double getOneMinuteRate() {
        tickIfNecessary();
        return m1Rate.getRate(TimeUnit.SECONDS);
    }
}

@@ -1712,12 +1712,105 @@
 RVAL
- && 
+) %7B%0A            final long newIntervalStartTick = newTick - age %25 TICK_INTERVAL;%0A            if (
 last
@@ -1836,24 +1836,37 @@
 oldTick, new
+IntervalStart
 Tick)) %7B%0A   
@@ -1866,32 +1866,36 @@
 ) %7B%0A            
+ 
+   
 final long requi
@@ -1938,16 +1938,20 @@
         
+    
 for (lon
@@ -1997,24 +1997,28 @@
             
+   
+ 
 m1Rate.tick(
@@ -2012,32 +2012,36 @@
  m1Rate.tick();%0A
+    
                 
@@ -2047,32 +2047,36 @@
  m5Rate.tick();%0A
+    
                 
@@ -2083,32 +2083,50 @@
 m15Rate.tick();%0A
+                %7D%0A
             %7D%0A  

make sure that EWMA intervals are adjacent