package permutace;

import java.awt.*;
import java.awt.event.*;
import java.applet.*;

public class AppletPermutace extends Applet {

  // implementace GUI
  boolean isStandalone = false;
  private Label lable_velikost;
  private Label lable_index;
  private Label vysledekLB;
  private TextField velikost;
  private TextField index;
  private Button buttonGo;

  private GridBagLayout gbl;
  private GridBagConstraints gbc;

  private class ButtonGoClick implements ActionListener {
    public void actionPerformed(ActionEvent p) {
      String result =  countPerm(velikost.getText(),index.getText());
      vysledekLB.setText(result);
    }
  }

  private void vlozComponentu(Component c, int gridx, int gridy) {
    gbc.gridx = gridx;
    gbc.gridy = gridy;
    gbl.setConstraints(c,gbc);
    add(c);
  }

  private void initMetoda() {
    // implementace GUI
         lable_velikost = new Label("delka permutace N: ");
    lable_index = new Label("index permutace I: ");
    velikost = new TextField("");
    vysledekLB = new Label("");
    index = new TextField("");
    buttonGo = new Button("Spocti");
    buttonGo.addActionListener(new ButtonGoClick());
    gbl = new GridBagLayout();
    this.setLayout(gbl);
    this.setBackground(Color.white);
    gbc = new GridBagConstraints();
    gbc.insets = new Insets(2,2,2,2);
    gbc.anchor = gbc.WEST;
    vlozComponentu(lable_velikost,0,0);
    gbc.weightx = 1.0;
    gbc.fill = GridBagConstraints.HORIZONTAL;
    vlozComponentu(velikost,0,1);
    gbc.anchor = gbc.WEST;
    vlozComponentu(lable_index,0,2);
    gbc.weightx = 1.0;
    gbc.fill = GridBagConstraints.HORIZONTAL;
    vlozComponentu(index,0,3);
    gbc.fill = GridBagConstraints.NONE;
    gbc.weightx = 0.0;
    gbc.anchor = gbc.CENTER;
    vlozComponentu(buttonGo,0,4);
    gbc.anchor = gbc.CENTER;
    gbc.fill = GridBagConstraints.HORIZONTAL;
    vysledekLB.setSize(200,20);
    vlozComponentu(vysledekLB,0,5);
    }

  // Initialize appletu
  public void init() {
    try {
      initMetoda();
    }
    catch(Exception e) {
      e.printStackTrace();
    }
  }
    // funkce pro vypocet I-te permutace
    public static String countPerm(String NStr, String IStr) {
         int NValue = 0;   // N je delka permutace
         int IValue = 0;   // I je index hledane permutace
         try {             // pokus o prevedeni N na cislo 
           Integer N = new Integer(NStr);
           NValue = N.intValue();
         } catch(NumberFormatException ex) {
           return "CHYBA N neni cislo nebo je mimo rozsah";
         }
         // kontrola rozsahu N maximum je N = 12 protoze 13! = 6227020800 > integer.MAX_VALUE = 2147483647 
         if ((NValue > 12) || (NValue < 1)) { return "CHYBA N mimo rozsah <1,12>"; }

         try {            // pokus o prevedeni I na cislo 
           Integer I = new Integer(IStr);
           IValue = I.intValue();
         } catch(NumberFormatException ex) {
           return "CHYBA I neni cislo nebo je mimo rozsah";
         }

         int rad = 1;     // vypocet maximalniho radu permutace = N! 
         for (int x = NValue; x > 0; x--) {
           rad = rad * x;
         }
                          // overeni zda I je v intervalu <0 ; N!-1> 
         if ((IValue >= rad) || (IValue < 0)) { return "CHYBA I mimo rozsah <0,"+(new Long(rad-1)).toString()+">"; }
         rad = rad / NValue;

         String chars = new String("0123456789AB");  // pojmenovani jednotlivych dostupnych clenu premutace 
         String perm = new String("");               // inicializace vysledne premutace 

         while (NValue > 1) {                        // pres vsechny cleny permutace 
           NValue--;
           int divx = IValue / rad;                  // urci N-ty clen permutace
           IValue = IValue % rad;                    // urci zbytek po N-tem clenu permutace
           perm = perm + chars.charAt(divx);         // pridej N-ty clen permutace do vysledne permutace
           chars = chars.substring(0,divx) + chars.substring(divx+1);  // a odstran ho z dostupnych clenu
           rad = rad / NValue;                       // sniz rad permutace 
           }

         perm = "Permutace = "+ perm + chars.charAt(0); // pouzij posledni dostupny clen permutace
         return perm;                                // vrat vypoctenou permutaci
    }
}