import java.awt.*;

import java.awt.event.*;

import java.lang.*;

import java.lang.Math;

import java.text.*;



public class RelV2 extends java.applet.Applet 

  implements Runnable {



  Canvas oscillators;

  Label riverSpeedLabel, boatSpeedLabel, boatAngleLabel,

        riverSpeedS, boatSpeedS, boatAngleS;

  Button Start;

  Thread runner;

  Scrollbar riverSpeedscroll, boatSpeedscroll, boatAnglescroll;

  int riverSpeed, boatSpeed, boatAngle, ballDiameter, index;

  int[] xpos = new int[11];

  double[] x = new double[11];

  int[] ypos = new int[11];

  double[] y = new double[11];

  double[] vectorX = new double[7];

  int[] vectorXpos = new int[7];

  double[] vectorY = new double[7];

  int[] vectorYpos = new int[7];

  int[] floaterX = new int[5];

  int[] floaterY = new int[5];

  double riverV, boatV, boatA, vRSX, vRSY, vBRX, vBRY, vBSX, vBSY,

          crossTime, xDistance;

  double pi = 3.141592653589793238468;



  Image offscreenImg;

  Graphics offscreenG;



  boolean startFlag;



  void buildConstraints(GridBagConstraints gbc, int gx, int gy, 

      int gw, int gh,

      int wx, int wy) {

	gbc.gridx = gx;

	gbc.gridy = gy;

	gbc.gridwidth = gw;

	gbc.gridheight = gh;

	gbc.weightx = wx;

	gbc.weighty = wy;

  }



  public void init() {

    GridBagLayout gridbag = new GridBagLayout();

    GridBagConstraints constraints = new GridBagConstraints();

    setLayout(gridbag);





    // River speed text

    buildConstraints(constraints, 0, 0, 1, 1, 20, 5);

    constraints.fill = GridBagConstraints.NONE;

    constraints.anchor = GridBagConstraints.EAST;

    Label riverSpeedLabel = new Label("Speed of the river (m/s):", Label.CENTER);

    gridbag.setConstraints (riverSpeedLabel, constraints);

    add(riverSpeedLabel);



    // River speed scrollbar label

    buildConstraints(constraints, 2, 0, 1, 1, 20, 0);

    constraints.fill = GridBagConstraints.HORIZONTAL;

    riverSpeedS = new Label("2", Label.LEFT);

    riverSpeed = 2;

    gridbag.setConstraints (riverSpeedS, constraints);

    add(riverSpeedS);



    // River speed scrollbar

    buildConstraints(constraints, 1, 0, 1, 1, 20, 0);

    constraints.fill = GridBagConstraints.HORIZONTAL;

    constraints.anchor = GridBagConstraints.WEST;

    riverSpeedscroll = new Scrollbar(Scrollbar.HORIZONTAL, 2, 1, 0, 5);

    gridbag.setConstraints (riverSpeedscroll, constraints);

    add(riverSpeedscroll);



    // boat speed text

    buildConstraints(constraints, 0, 1, 1, 1, 20, 5);

    constraints.fill = GridBagConstraints.NONE;

    constraints.anchor = GridBagConstraints.EAST;

    Label boatSpeedLabel = new Label("Speed of the boat (m/s):", Label.CENTER);

    gridbag.setConstraints (boatSpeedLabel, constraints);

    add(boatSpeedLabel);



    // boat speed scrollbar label

    buildConstraints(constraints, 2, 1, 1, 1, 20, 0);

    constraints.fill = GridBagConstraints.HORIZONTAL;

    boatSpeedS = new Label("5", Label.LEFT);

    boatSpeed = 5;

    gridbag.setConstraints (boatSpeedS, constraints);

    add(boatSpeedS);



    // boat speed scrollbar

    buildConstraints(constraints, 1, 1, 1, 1, 20, 0);

    constraints.fill = GridBagConstraints.HORIZONTAL;

    constraints.anchor = GridBagConstraints.WEST;

    boatSpeedscroll = new Scrollbar(Scrollbar.HORIZONTAL, 5, 1, 1, 12);

    gridbag.setConstraints (boatSpeedscroll, constraints);

    add(boatSpeedscroll);



    // boat angle text

    buildConstraints(constraints, 0, 2, 1, 1, 20, 5);

    constraints.fill = GridBagConstraints.NONE;

    constraints.anchor = GridBagConstraints.EAST;

    Label boatAngleLabel = new Label("Boat angle (degrees):", Label.CENTER);

    gridbag.setConstraints (boatAngleLabel, constraints);

    add(boatAngleLabel);



    // boat angle scrollbar label

    buildConstraints(constraints, 2, 2, 1, 1, 20, 0);

    constraints.fill = GridBagConstraints.HORIZONTAL;

    boatAngleS = new Label("0", Label.LEFT);

    boatAngle = 0;

    gridbag.setConstraints (boatAngleS, constraints);

    add(boatAngleS);



    // boat angle scrollbar

    buildConstraints(constraints, 1, 2, 1, 1, 20, 0);

    constraints.fill = GridBagConstraints.HORIZONTAL;

    constraints.anchor = GridBagConstraints.WEST;

    boatAnglescroll = new Scrollbar(Scrollbar.HORIZONTAL, 0, 2, -30, 30);

    gridbag.setConstraints (boatAnglescroll, constraints);

    add(boatAnglescroll);



    // Start button

    buildConstraints(constraints, 1, 3 , 1, 1, 0, 10);

    constraints.fill = GridBagConstraints.HORIZONTAL;

    constraints.anchor = GridBagConstraints.WEST;

    Start = new Button("Start");

    gridbag.setConstraints (Start, constraints);

    add(Start);



    // canvas

    buildConstraints(constraints, 0, 4, 3, 1, 0, 80);

    constraints.fill = GridBagConstraints.HORIZONTAL;

    oscillators = new Canvas();

    gridbag.setConstraints (oscillators, constraints);

    add(oscillators);



    offscreenImg = createImage(this.size().width, this.size().height);

    offscreenG = offscreenImg.getGraphics();

  }



  public void start() {

    if (runner == null); {

      runner = new Thread(this);

      runner.start();

    }

  }



  public void stop() {

    if (runner != null) {

      runner.stop();

      runner = null;

    }

  }



  public void run() {



    int i, temp;

    double xOrigin, yOrigin, kAngle, scale, tempA, arrowScale, riverScale;

    ballDiameter = 16;

    kAngle = pi/180.0;

    yOrigin = 380.0;

    xOrigin = 150.0;

    scale = 10.0;

    arrowScale = 1.2*scale;

    startFlag = false;



    for (i=0; i<=4; i++) {

     floaterX[i] = (int)(10+250*Math.random());

     floaterY[i] = (int)(yOrigin - 10 - 140*Math.random());

    }



    while (true) {

      index = 0;

      riverV = riverSpeed;

      boatV = boatSpeed;

      boatA = kAngle*boatAngle;



	vRSX = riverV;

      vRSY = 0.0;

      vBRX = boatV*Math.sin(boatA);

      vBRY = boatV*Math.cos(boatA);

      vBSX = vBRX + vRSX;

      vBSY = vBRY + vRSY;

      if (Math.abs(vBSX) < 0.000001) vBSX = 0.0;



      x[0] = xOrigin-(ballDiameter/2);

      xpos[0] = (int)(x[0]);



      vectorX[0] = xOrigin;

      vectorX[1] = vectorX[0]+scale*vBRX;

	temp=270-boatAngle-30;

      tempA = kAngle*temp;

      vectorX[2] = vectorX[1]+arrowScale*Math.cos(tempA);

	temp=270-boatAngle+30;

      tempA = kAngle*temp;

      vectorX[3] = vectorX[1]+arrowScale*Math.cos(tempA);

      vectorX[4] = vectorX[1]+scale*vRSX;

	temp=180-30;

      tempA = kAngle*temp;

      vectorX[5] = vectorX[4]+arrowScale*Math.cos(tempA);

	temp=180+30;

      tempA = kAngle*temp;

      vectorX[6] = vectorX[4]+arrowScale*Math.cos(tempA);



      y[0] = yOrigin-ballDiameter;

      ypos[0] = (int)(y[0]);



      vectorY[0] = yOrigin-(ballDiameter/2);

      vectorY[1] = vectorY[0]-scale*vBRY;

	temp=270-boatAngle-30;

      tempA = kAngle*temp;

      vectorY[2] = vectorY[1]-arrowScale*Math.sin(tempA);

	temp=270-boatAngle+30;

      tempA = kAngle*temp;

      vectorY[3] = vectorY[1]-arrowScale*Math.sin(tempA);

      vectorY[4] = vectorY[1]-scale*vRSY;

	temp=180-30;

      tempA = kAngle*temp;

      vectorY[5] = vectorY[4]+arrowScale*Math.sin(tempA);

	temp=180+30;

      tempA = kAngle*temp;

      vectorY[6] = vectorY[4]+arrowScale*Math.sin(tempA);



      for (i=0; i <=6; i++) {

           vectorXpos[i] = (int)(vectorX[i]);

           vectorYpos[i] = (int)(vectorY[i]);

      }



      for (i=0; i<=4; i++) {

        floaterX[i] = floaterX[i]+riverSpeed;

        if (floaterX[i] > 290) {

         floaterX[i] = 10;

         floaterY[i] = (int)(yOrigin - 10 - 140*Math.random());

        }

      }



      crossTime = 50.0/vBSY;

      xDistance = vBSX*crossTime;



      riverScale = (160 - ballDiameter)/10.0;

      

      while (startFlag) {



        while (startFlag) { 

          index = index +1;

          if (index > 10 ) {

            index = 10;

          }

          x[index] = x[0]+riverScale*index*vBSX/vBSY;

          y[index] = y[0]-riverScale*index;



          xpos[index] = (int)(x[index]);

          ypos[index] = (int)(y[index]);



          for (i=0; i<=4; i++) {

           floaterX[i] = floaterX[i]+riverSpeed;

           if (floaterX[i] > 290) {

            floaterX[i] = 10;

            floaterY[i] = (int)(yOrigin - 10 - 140*Math.random());

           }

         }



         repaint();

          try { Thread.sleep(150); }

          catch (InterruptedException e) { }

       } 

    }



     repaint();

     try { Thread.sleep(150); }

     catch (InterruptedException e) { }

     }

  }



  public void update(Graphics g) {

    paint(g);

  }

     

  public void paint(Graphics g) {



    int i;



     // Draw background

   offscreenG.setColor(Color.lightGray);

   offscreenG.fillRect(0,0,560,200);

   offscreenG.setColor(Color.white);

   offscreenG.fillRect(0,200,560,430);



   // Draw mass

    NumberFormat nf = NumberFormat.getInstance();

    nf.setMaximumFractionDigits(4);

    offscreenG.setColor(Color.black);

    offscreenG.drawLine(10, 220, 290, 220);

    offscreenG.drawLine(10, 380, 290, 380);

    offscreenG.drawLine(150, 210, 150, 220);

    offscreenG.drawLine(150, 380, 150, 390);

    offscreenG.setColor(Color.blue);

    for (i=0; i<=4; i++) {

    offscreenG.drawOval(floaterX[i],floaterY[i],2,2);

    }

    offscreenG.drawLine(vectorXpos[1],vectorYpos[1],vectorXpos[4],vectorYpos[4]);

    if (riverSpeed > 0) {

      offscreenG.drawLine(vectorXpos[4],vectorYpos[4],vectorXpos[5],vectorYpos[5]);

      offscreenG.drawLine(vectorXpos[4],vectorYpos[4],vectorXpos[6],vectorYpos[6]);

    }

    offscreenG.drawString("Velocity of the river relative to the shore", 300, 210);

    offscreenG.drawString("X component : Vrsx = " + nf.format(vRSX) + " m/s", 310, 228);

    offscreenG.drawString("Y component : Vrsy = " + nf.format(vRSY) + " m/s", 310, 246);

    offscreenG.setColor(Color.red);

    if (xpos[index]< 285)

       offscreenG.drawOval(xpos[index],ypos[index],ballDiameter,ballDiameter);

    offscreenG.drawLine(vectorXpos[0],vectorYpos[0],vectorXpos[1],vectorYpos[1]);

    offscreenG.drawLine(vectorXpos[1],vectorYpos[1],vectorXpos[2],vectorYpos[2]);

    offscreenG.drawLine(vectorXpos[1],vectorYpos[1],vectorXpos[3],vectorYpos[3]);

    offscreenG.drawString("Velocity of the boat relative to the river", 300, 266);

    offscreenG.drawString("X component : Vbrx = " + nf.format(vBRX) + " m/s", 310, 284);

    offscreenG.drawString("Y component : Vbry = " + nf.format(vBRY) + " m/s", 310, 302);

    offscreenG.setColor(Color.black);

    offscreenG.drawLine(vectorXpos[0],vectorYpos[0],vectorXpos[4],vectorYpos[4]);

    offscreenG.drawString("Velocity of the boat relative to the shore", 300, 322);

    offscreenG.drawString("X component : Vbsx = " + nf.format(vBSX) + " m/s", 310, 340);

    offscreenG.drawString("Y component : Vbsy = " + nf.format(vBSY) + " m/s", 310, 358);

    offscreenG.drawString("Time to cross river = " + nf.format(crossTime) + " s", 300, 378);

    offscreenG.drawString("Distance traveled in x direction = " + nf.format(xDistance) + " m", 300, 396);

    offscreenG.drawString("(when the boat reaches the far shore) ", 310, 414);

    g.drawImage(offscreenImg,0,0,this);

  }



  public void destroy() {

     offscreenG.dispose();

  }



  public boolean action (Event evt, Object arg) {



    if (evt.target instanceof Button) {



      if ((Button)evt.target == Start) {



        if (Start.getLabel().equals("Start")) {

          startFlag = true;

          Start.setLabel("Reset");

        }



        else {

          startFlag = false;

          Start.setLabel("Start");

        }

      }

    }

    else return super.action(evt, arg);

    return true;

  }



  public boolean handleEvent(Event evt) {



    if (evt.target instanceof Scrollbar) {

      if ((Scrollbar)evt.target == riverSpeedscroll) {

        riverSpeed = ((Scrollbar)evt.target).getValue();

        riverSpeedS.setText(String.valueOf(riverSpeed));

      }

      else if ((Scrollbar)evt.target == boatSpeedscroll) {

        boatSpeed = ((Scrollbar)evt.target).getValue();

        boatSpeedS.setText(String.valueOf(boatSpeed));

      }

      else if ((Scrollbar)evt.target == boatAnglescroll) {

        boatAngle = ((Scrollbar)evt.target).getValue();

        boatAngleS.setText(String.valueOf(boatAngle));

      }

	repaint();

    }

    else return super.handleEvent(evt);

    return true;

  }

}