// Exercise 2.2.2 (Solution published at http://algs4.cs.princeton.edu/)
package algs22;
import stdlib.*;
import java.awt.Font;
/* ***********************************************************************
 *  Compilation:  javac TraceMerge.java
 *  Execution:    java  TraceMerge input
 *
 *  Mergesort the sequence of strings specified as the command-line
 *  arguments and show the detailed trace.
 *
 *  % java TraceMerge MERGESORTEXAMPLE
 *
 *************************************************************************/

public class XTraceMerge {
  private static int line = 0;

  private static void merge(String[] a, String[] aux, int lo, int m, int hi) {

    // copy to aux[]
    for (int k = lo; k <= hi; k++) {
      aux[k] = a[k];
    }

    // merge back to a[]
    int i = lo, j = m+1;
    for (int k = lo; k <= hi; k++) {
      if      (i > m)                a[k] = aux[j++];
      else if (j > hi)               a[k] = aux[i++];
      else if (less(aux[j], aux[i])) a[k] = aux[j++];
      else                           a[k] = aux[i++];
    }

  }

  // mergesort a[lo..hi] using auxiliary array aux[lo..hi]
  private static void sort(String[] a, String[] aux, int lo, int hi) {
    if (hi <= lo) return;
    int m = lo + (hi - lo) / 2;
    sort(a, aux, lo, m);
    sort(a, aux, m + 1, hi);
    merge(a, aux, lo, m, hi);
    draw(a, lo, m, hi);
    line++;
  }

  public static void sort(String[] a) {
    String[] aux = new String[a.length];
    sort(a, aux, 0, a.length-1);
  }

  // exchange a[i] and a[j]
  private static void exch(String[] a, int i, int j) {
    String swap = a[i];
    a[i] = a[j];
    a[j] = swap;
  }

  // is v < w ?
  private static boolean less(String v, String w) {
    return (v.compareTo(w) < 0);
  }


  // draw the contents of the array, with a[lo] to a[hi] in black
  private static void draw(String[] a, int lo, int m, int hi) {
    StdDraw.setPenColor(StdDraw.BLACK);
    StdDraw.text(-2.50, line, m  + "");
    StdDraw.setPenColor(StdDraw.BOOK_RED);
    StdDraw.text(-3.75, line, lo + "");
    StdDraw.text(-1.25, line, hi + "");
    for (int i = 0; i < a.length; i++) {
      if (i >= lo && i <= hi) StdDraw.setPenColor(StdDraw.BLACK);
      else                    StdDraw.setPenColor(StdDraw.LIGHT_GRAY);
      StdDraw.text(i, line, a[i]);
    }
  }

  // display header
  private static void header(String[] a) {
    int N = a.length;
    StdDraw.setPenColor(StdDraw.BLACK);
    StdDraw.text(N/2, -3, "a[ ]");
    for (int i = 0; i < N; i++)
      StdDraw.text(i, -2, i + "");
    StdDraw.text(-3.75, -2, "lo");
    StdDraw.text(-2.50, -2, "m");
    StdDraw.text(-1.25, -2, "hi");
    StdDraw.setPenColor(StdDraw.BOOK_RED);
    StdDraw.line(-4, -1.65, N-.5, -1.65);
    StdDraw.setPenColor(StdDraw.BLACK);
    for (int i = 0; i < a.length; i++)
      StdDraw.text(i, -1, a[i]);
  }

  // display footer
  private static void footer(String[] a) {
    int N = a.length;
    StdDraw.setPenColor(StdDraw.BLACK);
    for (int i = 0; i < a.length; i++)
      StdDraw.text(i, N-1, a[i]);
  }


  // test client
  public static void main(String[] args) {
    args = new String[] { "EASYQUESTION" };

    // parse command-line argument as an array of 1-character strings
    String s = args[0];
    int N = s.length();
    String[] a = new String[N];
    for (int i = 0; i < N; i++)
      a[i] = s.substring(i, i+1);

    // set canvas size
    StdDraw.setCanvasSize(30*(N+3), 30*(N+3));
    StdDraw.setXscale(-4, N+1);
    StdDraw.setYscale(N+1, -4);
    StdDraw.setFont(new Font("SansSerif", Font.PLAIN, 13));

    // display the header
    header(a);

    // sort the array and display trace
    sort(a);

    // display the footer
    footer(a);
  }

}