/**
 * 
 */
package de.fhswf.in.inf.java1.aufgabe6;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Random;
import java.util.Vector;

/**
 * Class that benchmarks List implementations.
 *
 * @author $Author: $
 * @version $Revision: $, $Date: $ UTC
 */
public final class ListBenchmark
{

   private static final Integer TESTOBJ = new Integer(214);

   /**
    * Prevents instantiation of the utility class.
    *
    */
   private ListBenchmark()
   {
   }

   /**
    * Starts a benchmark of different Lists and different test cases.
    *
    */
   public static void startBenchmark()
   {
      final int times = 100000;

      benchmarkGrouping("ArrayList", new ArrayList<Integer>(times), times);
      benchmarkGrouping("Vector", new Vector<Integer>(times), times);
      benchmarkGrouping("LinkedList", new LinkedList<Integer>(), times);

   }

   /**
    * Groups the 3 different benchmark versions together.
    *
    * @param variant
    *           Name of the list type.
    * @param list
    *           The list which will be benchmarked.
    * @param times
    *           How often will be inserted.
    */
   private static void benchmarkGrouping(String variant, List<Integer> list,
         int times)
   {
      System.out.print(variant + " am Anfang: ");
      System.out.println(benchmarkAtBeginning(list, times) + " ms");
      System.out.print(variant + " am Ende: ");
      System.out.println(benchmarkAtEnding(list, times) + " ms");
      System.out.print(variant + " zufälliger Index: ");
      System.out.println(benchmarkAtRandom(list, times) + " ms");
   }

   /**
    * Inserts new value at the beginning of the list.
    *
    * @param list
    *           List to be tested.
    * @param times
    *           How many inserts are done.
    * @return Time in milliseconds that the action took.
    */
   private static long benchmarkAtBeginning(List<Integer> list, int times)
   {
      long start = System.currentTimeMillis(); // Gets current time in µs

      for (int i = 0; i < times; i++)
      {
         list.add(0, TESTOBJ);
      }

      return (System.currentTimeMillis() - start); // Returns runtime
   }

   /**
    * Inserts new value at the end of the list.
    *
    * @param list
    *           List to be tested.
    * @param times
    *           How many inserts are done.
    * @return Time in milliseconds that the action took.
    */
   private static long benchmarkAtEnding(List<Integer> list, int times)
   {
      long start = System.currentTimeMillis(); // Gets current time in µs

      for (int i = 0; i < times; i++)
      {
         list.add(TESTOBJ);
      }

      return (System.currentTimeMillis() - start); // Returns runtime
   }

   /**
    * Inserts new value at a random index of the list.
    *
    * @param list
    *           List to be tested.
    * @param times
    *           How many inserts are done.
    * @return Time in milliseconds that the action took.
    */
   private static long benchmarkAtRandom(List<Integer> list, int times)
   {

      int[] randVal = new int[times];
      Random rand = new Random();

      for (int i = 0; i < randVal.length; i++)
      {
         randVal[i] = rand.nextInt(list.size() + i + 1);
      }

      long start = System.currentTimeMillis(); // Gets current time in µs

      for (int i = 0; i < times; i++)
      {
         list.add(randVal[i], TESTOBJ);
      }

      return (System.currentTimeMillis() - start); // Returns runtime
   }
}