package rebelsky.exam4;

import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.Random;
import java.util.Vector;

/**
 * Something that knows how to test mergesorters.
 *
 * @author Samuel A. Rebelsky
 * @version 1.0 of December 2005
 */
public class MSTester
{
  /**
   * How many tests do we do per size?
   */
  static final int TESTS = 5;

  // +------+----------------------------------------------------
  // | Main |
  // +------+

  public static void main(String[] args)
  {
    PrintWriter pen = new PrintWriter(System.out, true);
    MergeSorter<BigInteger> sorter = new MergeSorter<BigInteger>();

    for (int i = 1; i <= 2048; i *= 2) {
      pen.println("Testing for size " + i);
      // Do the appropriate number of tests.
      for (int test = 0; test < TESTS; test++) {
        pen.print("  Test " + test + ": ");
        System.gc();
        sorter.reset();
        boolean result = onetest(sorter, i, pen);
        pen.println(sorter.steps() + " steps.");
        // Give up for bad results
        if (!result) { return; }
      } // for (test)
    } // for
  } // main(String[])

  // +----------------+------------------------------------------
  // | Helper Methods |
  // +----------------+

  /**
   * Run a test with a vector of size n on sorter, using log to report 
   * errors.  Returns true if the test succeeded and false otherwise.
   */

  static boolean onetest(OutOfPlaceVectorSorter<BigInteger> sorter, 
                         int n, 
                         PrintWriter log)
  {
    // Problems encountered
    String problem = null;
    // Build a sorted vector (which makes it easy to check whether the
    // result is correct).
    Vector<BigInteger> original = VectorUtils.randomSortedVector(n);
    Vector<BigInteger> sortme = VectorUtils.duplicate(original);
    VectorUtils.permute(sortme);
    // Try to sort it
    sortme = sorter.sort(sortme, new BigIntegerComparator());
    // Make sure the sorted thing is the right size.
    if (sortme.size() != n) {
      problem = "result vector has incorrect size";
    }
    int i = 0;
    while ((problem == null) && (i < n)) {
      if (!original.get(i).equals(sortme.get(i))) {
        problem = "mismatch in position " + Integer.toString(i);
      } // if
      ++i;
    }
    if (problem == null) {
      return true;
    }
    else {
      log.println("Failed to correctly sort a vector of size " + n
                  + " because " + problem + ".");
      log.println("  Original: " + original);
      log.println("  'Sorted': " + sortme);
      return false;
    }
  } // onetest(OutOfPlaceVectorSorter<BigInteger>, int, PrintWriter)

} // MSTester