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// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
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// ***************************************************************************************************************************
package org.apache.juneau.utils;

import java.lang.reflect.*;
import java.util.*;
import java.util.concurrent.atomic.*;

import org.apache.juneau.annotation.*;
import org.apache.juneau.marshall.*;

/**
 * Basic timing information.
 *
 * Keeps track of number of starts/finishes on tasks and keeps an average run time.
 */
@Bean(bpi="method,runs,running,errors,minTime,maxTime,avgTime,totalTime,exceptions")
public class MethodExecStats implements Comparable<MethodExecStats> {

   private String method;
   private WeightedAverage avgTime = new WeightedAverage();
   private volatile int minTime = -1, maxTime;

   private AtomicInteger
      starts = new AtomicInteger(),
      finishes = new AtomicInteger(),
      errors = new AtomicInteger();

   private AtomicLong
      totalTime = new AtomicLong();

   private StackTraceDatabase stackTraceDb;

   /**
    * Constructor.
    *
    * @param method Arbitrary label.  Should be kept to less than 50 characters.
    * @param stackTraceStopClass Don't calculate stack traces when this class is encountered.
    */
   public MethodExecStats(Method method, Class<?> stackTraceStopClass) {
      this.method = method.getDeclaringClass().getSimpleName() + "." + method.getName();
      this.stackTraceDb = new StackTraceDatabase(-1, stackTraceStopClass);
   }

   /**
    * Constructor.
    *
    * @param method Arbitrary label.  Should be kept to less than 50 characters.
    */
   public MethodExecStats(Method method) {
      this(method, MethodInvoker.class);
   }

   /**
    * Call when task is started.
    */
   public void started() {
      starts.incrementAndGet();
   }

   /**
    * Call when task is finished.
    * @param nanoTime The execution time of the task in nanoseconds.
    */
   public void finished(long nanoTime) {
      finishes.incrementAndGet();
      int milliTime = (int)(nanoTime/1_000_000);
      totalTime.addAndGet(nanoTime);
      avgTime.add(1, nanoTime);
      minTime = minTime == -1 ? milliTime : Math.min(minTime, milliTime);
      maxTime = Math.max(maxTime, milliTime);
   }

   /**
    * Call when an error occurs.
    * @param e The exception thrown.  Can be <jk>null</jk>.
    */
   public void error(Throwable e) {
      errors.incrementAndGet();
      stackTraceDb.add(e);
   }

   /**
    * Returns the method name of these stats.
    *
    * @return The method name of these stats.
    */
   public String getMethod() {
      return method;
   }

   /**
    * Returns the number of times the {@link #started()} method was called.
    *
    * @return The number of times the {@link #started()} method was called.
    */
   public int getRuns() {
      return starts.get();
   }

   /**
    * Returns the number currently running method invocations.
    *
    * @return The number of currently running method invocations.
    */
   public int getRunning() {
      return starts.get() - finishes.get();
   }

   /**
    * Returns the number of times the {@link #error(Throwable)} method was called.
    *
    * @return The number of times the {@link #error(Throwable)} method was called.
    */
   public int getErrors() {
      return errors.get();
   }

   /**
    * Returns the max execution time.
    *
    * @return The average execution time in milliseconds.
    */
   public int getMinTime() {
      return minTime == -1 ? 0 : minTime;
   }

   /**
    * Returns the max execution time.
    *
    * @return The average execution time in milliseconds.
    */
   public int getMaxTime() {
      return maxTime;
   }

   /**
    * Returns the average execution time.
    *
    * @return The average execution time in milliseconds.
    */
   public int getAvgTime() {
      return (int)avgTime.getValue() / 1_000_000;
   }

   /**
    * Returns the total execution time.
    *
    * @return The total execution time in milliseconds.
    */
   public long getTotalTime() {
      return totalTime.get() / 1_000_000;
   }

   /**
    * Returns information on all stack traces of all exceptions encountered.
    *
    * @return Information on all stack traces of all exceptions encountered.
    */
   public List<StackTraceInfo> getExceptions() {
      return stackTraceDb.getClonedStackTraceInfos();
   }

   @Override /* Object */
   public String toString() {
      return SimpleJson.DEFAULT.toString(this);
   }

   @Override /* Comparable */
   public int compareTo(MethodExecStats o) {
      return Long.compare(o.getTotalTime(), getTotalTime());
   }
}