// mathGraph.java

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

public class mathGraph extends Applet implements ActionListener, ItemListener{
  private int     maxDim;                   // 次元最大値
  private int     width, height, dimension; // 横幅・縦幅・次元
  private boolean flag;                     // 再描画の為のフラグ

  private CheckboxGroup cbg; // チェックボックス群
  private Checkbox []   cb;

  private Label     mes; // エラーメッセージ用ラベル
  private TextField byT; // 倍率

  private TextField [] tfX;
  private Label     [] lX;  // dimensionによって大きさが変わる
  private TextField    tfS; // y切片用テキストフィールド

  private Button submit, clear; // paint／clear ボタン

  public void init(){
/* * * * * * * * パラメータ受け取り＆セット * * * * * * * */
    int tmp = Integer.parseInt(getParameter("dimension"));
    maxDim  = tmp >= 0 ? tmp : 4;

    int    bg         = Integer.parseInt(getParameter("bgcolor"), 16);
    int    fontSize   = Integer.parseInt(getParameter("fontSize"));
    String fontFamily = getParameter("family");
    String fontBold   = getParameter("font");

    setLayout(new BorderLayout());
    setBackground(new Color(bg));

         if(fontBold.toLowerCase().equals("bold"))       setFont(new Font(fontFamily, Font.BOLD, fontSize));
    else if(fontBold.toLowerCase().equals("italic"))     setFont(new Font(fontFamily, Font.ITALIC, fontSize));
    else if(fontBold.toLowerCase().equals("bolditalic")) setFont(new Font(fontFamily, Font.BOLD+Font.ITALIC, fontSize));
    else                                                 setFont(new Font(fontFamily, Font.PLAIN, fontSize));
/* * * * * * * * * * * * ここまで * * * * * * * * * * * * */

    width  = getSize().width;
    height = getSize().height;

    flag      = false;  // flag初期値はfalse
    dimension = maxDim; // dimensionの初期値は最大値

    tfX = new TextField[dimension];
    lX  = new Label[dimension];

    Panel byP = new Panel(new FlowLayout());
    byP.add(new Label("倍率ドン！"));
    byP.add(byT = new TextField("10", 3));
    byP.add(submit = new Button("更にドン！"));
    byP.add(clear  = new Button("竹下さんに全部"));

    Panel p1 = new Panel(new FlowLayout());
    p1.add(new Label("y ="));

    for(int i = dimension-1; i >= 0; i--){
      tfX[i] = new TextField("1", 2);
      lX[i]  = i != 0 ? new Label("x^" + Integer.toString(i+1) + " +") : new Label("x +");

      p1.add(tfX[i]);
      p1.add(lX[i]);
    }
    p1.add(tfS = new TextField("0", 3));

    Panel byP_p1 = new Panel(new GridLayout(2, 1));
    byP_p1.add(byP);
    byP_p1.add(p1);

    cbg = new CheckboxGroup();
    cb  = new Checkbox[dimension];

    Panel p3 = new Panel(new GridLayout(2, (int)Math.floor(dimension/2.0)));
    for(int i = 0; i < dimension; i++){
      p3.add(cb[i] = new Checkbox(i+1+"次",  cbg, true));
      cb[i].addItemListener(this); // 次元の数だけCheckboxとリスナの追加
    }

    Panel overPanel = new Panel(new FlowLayout());
    overPanel.add(byP_p1);
    overPanel.add(p3);

    Panel underPanel = new Panel(new BorderLayout());
    underPanel.add(mes = new Label());

    Panel finPanel = new Panel(new BorderLayout());
    finPanel.add(overPanel,  BorderLayout.NORTH);
    finPanel.add(underPanel, BorderLayout.SOUTH);

    add(finPanel, BorderLayout.SOUTH);

    submit.addActionListener(this);
    clear.addActionListener(this);
  }

  public void paint(Graphics g){
    mes.setText("");

    int xZero = width  / 2; // x軸の座標0
    int yZero = height / 2; // y軸の座標0

    if(!flag){
      g.clearRect(0, 0, width, height);

      g.setColor(Color.black);
      g.drawString("(0, 0)", xZero-35, yZero+15);

      for(int i = -1; i <= 1; i++){              // 太くするため三回描画
        g.drawLine(0, yZero+i, width, yZero+i);  // x軸
        g.drawLine(xZero+i, 0, xZero+i, height); // y軸
      }
    }
    else{
      double power = 1;
      try{ power = Math.abs(toDouble(byT.getText())); } // 倍率
      catch(NumberFormatException e){ errorMes("Input must be 'Hankaku' numbers."); }
      if(power == 0)      errorMes("Division by Zero.");

      double s = 0;
      try{ s = toDouble(tfS.getText()); }
      catch(NumberFormatException e){ errorMes("Input must be 'Hankaku' numbers."); }
      s *= power;
        // y切片取得

      double [] x = new double[dimension]; // 次元に合った大きさに

      for(int i = 0; i < dimension; i++){
        String tmp  = tfX[i].getText();
        try{ x[i] = tmp.equals("") ? 0 : toDouble(tmp); }
        catch(NumberFormatException e){ errorMes("Input must be 'Hankaku' numbers."); }
      }   // それぞれの次元の係数を取得

      double x1 = 65535, y1 = 65535; // あり得ない数字をフラグの代わりに
      double x2 = 0,     y2 = 0;

      g.setColor(new Color((int)(Math.random() * 0xFFFFFF)));
      for(double i = 0-xZero; i <= xZero; i+=power){ // xの増加量はpower（power pixelを１単位とする）
        x2 = xZero + i; // xの増加量は一定

        y2 = yZero - s; // まずy切片の計算
        for(int j = dimension; j >= 1; j--){
          double plus;
          if(j >= 2){
            double beki = Math.pow(i/power, j)/Math.pow(power, j-2);
            plus = x[j-1] > 0 ? beki : 0 - beki;
          }
          else plus = x[j-1] > 0 ? i : 0 - i;

          y2 -= plus * Math.abs(x[j-1]); // これで y＝（増加量×x）＾次元＋ｙ切片 となる
        }

        if(x1 != 65535 && y1 != 65535 && y2 >= 0-height && y2 <= height*2){
          // 座標が表示領域を大幅に超えていたりしたら描画しない

          g.drawLine((int)x1, (int)y1, (int)x2, (int)y2);
          try{ Thread.sleep(10); }
          catch(InterruptedException ie){ errorMes("割り込み発生？"); }
        }
        x1 = x2;
        y1 = y2;
      }
    }

    flag = false;
  }

  public void actionPerformed(ActionEvent e){
    if(e.getActionCommand().equals("更にドン！")){
      flag = true;
      repaint();
    }
    else{
      flag = false;
      repaint();
    }
  }

  public void itemStateChanged(ItemEvent e){
    for(int i = 1; i <= maxDim; i++){  // 何次方程式かを確かめて次元値に代入
      if(((String)e.getItem()).equals(i+"次")){
        dimension = i;
        break;
      }
    }

    for(int i = 0; i < maxDim; i++){
      if(i < dimension){
        tfX[i].setText("1");
        tfX[i].setVisible(true);
        lX[i].setVisible(true);
      }
      else{
        tfX[i].setText("0");
        tfX[i].setVisible(false);
        lX[i].setVisible(false);
      }
    }
  }

  private double toDouble(String val){
    return Double.valueOf(val).doubleValue();
  }

  public void update(Graphics g){
    paint(g);
  }

  private void errorMes(String s){
    mes.setText("Error: " + s);
    throw new IllegalArgumentException("Error message sent. At errorMes.");
  }
}