/*******************************************************************************
 * Copyright (c) 1998, 2012 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the 
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0 
 * which accompanies this distribution. 
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at 
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *      Oracle - initial impl
 ******************************************************************************/
package example;

import java.util.ArrayList;
import java.util.List;

/**
 * Generic performance test.
 * This allows executing a timed run and measures and logs the performance.
 * Logs the executions per run (minute), logs average and % stdev.
 */
public class PerformanceTest {

    public static int REPEATS = 5;
    public static int RUN_TIME = 60000; //60 seconds.

    /**
     * Measure the performance of the run.
     * Repeat the run REPEATS (5) times,
     * and measure the number of execution in RUN_TIME (60s).
     */
    public static PerformanceResult executeRun(String name, Runnable runnable) {
        System.out.println("Starting run: " + name);
        
        List<Integer> results = new ArrayList<Integer>();
        // Repeat the test and baseline for the number of repeats.
        for (int index = 0; index < REPEATS; index++) {
            long startTime, endTime;
            int executions = 0;
            System.gc();
            try {
                Thread.sleep(1000);
            } catch (InterruptedException ignore) {}
            startTime = System.currentTimeMillis();
            endTime = startTime;
            // Count how many times the test can be invoked in the run time.
            // This allows for the test run time to be easily changed.
            while ((startTime + RUN_TIME) >= endTime) {
                runnable.run();
                executions++;
                endTime = System.currentTimeMillis();
            }
            results.add(executions);
            System.out.println("Done run: " +  index + " for: " + name);
        }
        
        System.out.println("Completed run: " + name);

        PerformanceResult result = new PerformanceResult();
        result.testName = name;
        result.runRepeats = REPEATS;
        result.runTime = RUN_TIME;
        result.average = averageResults(results);
        result.max = maxResults(results);
        result.min = minResults(results);
        result.standardDeviation = standardDeviationResults(results);
        
        System.out.println("");
        System.out.println(result);
        System.out.println("");
        System.out.println("");
        
        return result;
    }

    /**
     * Compute the max of the results.
     */
    public static int maxResults(List<Integer> times) {
        int testMax = 0;
        for (int index = 0; index < times.size(); index++) {
            int time = (int)times.get(index);
            if (time > testMax) {
                testMax = time;
            }
        }
        return testMax;
    }

    /**
     * Compute the min of the results.
     */
    public static int minResults(List<Integer> times) {
        int testMin = 0;
        for (int index = 0; index < times.size(); index++) {
            int time = (int)times.get(index);
            if ((testMin == 0) || (time < testMin)) {
                testMin = time;
            }
        }
        return testMin;
    }

    /**
     * Filter max and min from results.
     */
    public static List<Integer> filterMaxMinResults(List<Integer> times) {
        List filteredTimes = new ArrayList(times);
        if (filteredTimes.size() > 3) {
            filteredTimes.remove((Integer)maxResults(times));
            filteredTimes.remove((Integer)minResults(times));
        }
        return filteredTimes;
    }

    /**
     * Compute the average of the results rejecting the min and max.
     */
    public static double averageResults(List<Integer> allTimes) {
        // Compute the average reject the min and max to improve consistency.
        List<Integer> times = filterMaxMinResults(allTimes);
        double testAverage = 0;
        for (int index = 0; index < times.size(); index++) {
            int time = (int)times.get(index);
            testAverage = testAverage + time;
        }
        testAverage = testAverage / times.size();
        return testAverage;
    }

    /**
     * Compute the standard deviation of the results rejecting the min and max.
     */
    public static double standardDeviationResults(List<Integer> allTimes) {
        // Compute the average reject the min and max to improve consistency.
        double testAverage = averageResults(allTimes);

        // Compute the standard deviation reject the min and max to improve consistency.
        List<Integer> times = filterMaxMinResults(allTimes);
        double testStandardDeviation = 0;
        for (int index = 0; index < times.size(); index++) {
            int time = (int)times.get(index);
            testStandardDeviation = testStandardDeviation + Math.pow(time - testAverage, 2);
        }
        testStandardDeviation = testStandardDeviation / times.size();
        testStandardDeviation = Math.sqrt(testStandardDeviation);
        // As percent of average
        testStandardDeviation = (testStandardDeviation / testAverage) * 100;
        return testStandardDeviation;
    }
}