// ***************************************************************************************************************************
// * 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.juneau.mstat;

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

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

/**
 * 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 volatile int minTime = -1, maxTime;

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

   private AtomicLong
      totalTime = new AtomicLong();

   private ExceptionStore 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 ExceptionStore(-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);
      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() {
      int runs = getRuns();
      return runs == 0 ? 0 : (int)(getTotalTime() / runs);
   }

   /**
    * 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<ExceptionStats> getExceptions() {
      return stackTraceDb.getClonedStats();
   }

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

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