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

public class osc extends Applet implements Runnable{	
	Thread moveThread;
	private static final int MOVEPAUSE = 40;
	public boolean myGo=false;
	public boolean myReset=true;
	mycan c;
	public Image offScreenImage;
	double kSpring = 16.0;
	double mSpring =  1.0;
	
	public void start()  {
		// Start up a thread
		if(myGo) {
			if(moveThread == null){
				moveThread = new Thread(this);
				moveThread.start();
			}
		}
	}
	
	public void stop()  {
		// Stop the thread we started
		if(moveThread != null){
			moveThread.stop();
			try {
				moveThread.join();
			}
			catch (InterruptedException e) { }
		}
		moveThread=null;
	}
		
	public void run() {
		while (true){
			try {
				moveThread.sleep(MOVEPAUSE);
			}catch(InterruptedException e) {
			}
			c.repaint();
		}
	}
	
	public void setMyLogicals(boolean goButton,boolean reset){
		myGo=goButton;
		myReset=reset;
		if(myGo){
			if(moveThread == null) {
				moveThread = new Thread(this);
				moveThread.start();
			}
		} else {
			if(moveThread != null) {
				moveThread.stop();
				try {
					moveThread.join();
				}
				catch (InterruptedException e) { }
			}
			moveThread = null;
		}
		if(myReset){
			c.repaint();
		}
	}
	
	public void init() {
		super.init();
		int i,j,x;
		setBackground(Color.white);
		offScreenImage = createImage(500,300);
		c = new mycan(this,offScreenImage);
		
		//{{INIT_CONTROLS
		setLayout(new BorderLayout(0,0));
		resize(500,350);
		p1 = new java.awt.Panel();
		p1.setLayout(new GridLayout(0,5,3,3));
		p1.reshape(0,0,500,50);
		p1.setBackground(new Color(16777215));
		add("North", p1);
		goButton = new java.awt.Button("Start");
		goButton.setFont(new Font("TimesRoman", Font.BOLD, 14));
		goButton.setBackground(new Color(65280));
		p1.add(goButton);
		stopButton = new java.awt.Button("Stop");
		stopButton.setFont(new Font("TimesRoman", Font.BOLD, 14));
		stopButton.setBackground(new Color(16711680));
		p1.add(stopButton);
		resetButton = new java.awt.Button("Reset");
		resetButton.setFont(new Font("TimesRoman", Font.BOLD, 14));
		resetButton.setBackground(new Color(16762880));
		p1.add(resetButton);
		kLabel = new java.awt.Label("k=16 N/m",Label.CENTER);
		kLabel.setFont(new Font("TimesRoman", Font.PLAIN, 12));
		p1.add(kLabel);
		mLabel = new java.awt.Label("m=1 kg",Label.CENTER);
		mLabel.setFont(new Font("TimesRoman", Font.PLAIN, 12));
		p1.add(mLabel);
		label1 = new java.awt.Label("");
		p1.add(label1);
		label2 = new java.awt.Label("");
		p1.add(label2);
		label3 = new java.awt.Label("");
		p1.add(label3);
		kScroll = new java.awt.Scrollbar(Scrollbar.HORIZONTAL,16,16,1,100);
		p1.add(kScroll);
		mScroll = new java.awt.Scrollbar(Scrollbar.HORIZONTAL,10,10,1,100);
		p1.add(mScroll);
		
		add("Center",c);
		//}
}
		
	public boolean handleEvent(Event evt){
		String label;
		// Scrollbar
		if(evt.target == kScroll){
			kSpring = Math.round(kScroll.getValue());
			kLabel.setText("k="+kSpring+" N/m");
			c.omega = (double)Math.sqrt(kSpring/mSpring);
			c.it = 0;
			return true;
		} else if (evt.target == mScroll){
			mSpring = 0.1*Math.round(mScroll.getValue());
			mLabel.setText("m="+mSpring+" kg");
			c.omega = (double)Math.sqrt(kSpring/mSpring);
			c.it = 0;
			return true;
		// Read the four buttons and set the scenario
		} else if ((evt.target instanceof Button) && (evt.id == Event.ACTION_EVENT)){
			label=((Button) evt.target).getLabel();
		// Buttons
			if(label.equals("Start")){
				c.theColor++;
				if (c.theColor == 6) c.theColor = 1;
				setMyLogicals(true,false);
			}
			if(label.equals("Stop")){
				setMyLogicals(false,false);
			}
			if(label.equals("Reset")){
				setMyLogicals(false,true);
			}
			return true;
		} 
		return false;
	}

	//{{DECLARE_CONTROLS
	java.awt.Panel p1;
	java.awt.Label label1;
	java.awt.Label label2;
	java.awt.Label label3;
	java.awt.Label kLabel;
	java.awt.Label mLabel;
	java.awt.Scrollbar kScroll;
	java.awt.Scrollbar mScroll;
	java.awt.Button goButton;
	java.awt.Button stopButton;
	java.awt.Button resetButton;
	//}}
}

class mycan extends java.awt.Canvas
{
	boolean inTow=false;
	public int yMass = 250;
	public int xMass = 250;
	public int ytop = 240;
	public int y0 = 250;
	public int dy;
	public int it = 0;
	public int xMold, yMold;
	public double omega = 4.0;
	public int theColor = 1;
	Image offScreenImage;
	osc a;
	
	public mycan(osc myApplet, Image myImage) {
		offScreenImage = myImage;
		a = myApplet;
		resize(500,300);
		repaint();
	}

	public void update(Graphics g){
		Graphics offg = offScreenImage.getGraphics();
		//offg.setColor(getBackground());
		//offg.fillRect(0, 0, 500, 300);
		//offg.setColor(Color.white);
		paint(offg);
		g.drawImage(offScreenImage, 0, 0, this);
	}
	
	public void drawMass(Graphics g){
		g.setColor(Color.white);
		g.fillRect(0,0,50,300);
		g.setColor(Color.red);
		g.fillRect(2,ytop,46,20);
		g.setColor(Color.darkGray);
		g.fillRect(4,ytop+2,42,16);
		g.setColor(Color.black);
		g.fillOval(24,ytop+9,3,3);
		g.fillRect(0,0,50,10);
	}
	
	public void drawCoordinates(Graphics g){
		g.setColor(Color.white);   // white later
		g.fillRect(50,0,450,300);
		g.setColor(Color.black);
		g.drawLine(100,150,490,150);  // x-axis
		g.drawLine(200,148,200,152);
		g.drawLine(300,148,300,152);
		g.drawLine(400,148,400,152);
		g.drawString(" 5 s",190,165);
		g.drawString("10 s",290,165);
		g.drawString("15 s",390,165);
		g.drawString("t",490,145);
		g.drawLine(100,10,100,290);   // y-axis
		g.drawLine(98,50,102,50);
		g.drawLine(98,250,102,250);
		g.drawString(" 5 cm",55,50);		
		g.drawString("-5 cm",55,250);		
		g.drawString("x",105,10);		
	}

	public void drawSpring(int nt, int yhigh, int ylow, Graphics g){
		double denom = 2.0*nt + 1.0;
		g.drawLine(25,ylow,45,(int)(ylow+0.5*(yhigh-ylow)/denom));
		for (int i = 1; i < 2*nt; i=i+2){
			g.drawLine(45,(int)(ylow+(i-0.5)*(yhigh-ylow)/denom),
					    5,(int)(ylow+(i+0.5)*(yhigh-ylow)/denom));
			g.drawLine(45,(int)(ylow+(i+1.5)*(yhigh-ylow)/denom),
					    5,(int)(ylow+(i+0.5)*(yhigh-ylow)/denom));
		}
		g.drawLine(45,(int)(ylow+(2.*nt+0.5)*(yhigh-ylow)/denom),25,ytop);
	}	
	
	public void paint(Graphics g){
		// Draw everything
		if (a.myReset) {
			g.setColor(Color.white);
			g.fillRect(0, 0, 500, 300);
			drawCoordinates(g);  // makes new coordinate system
			it = 0;
			theColor = 1;
			a.myReset = false;
		}
		if (a.myGo && it < 400) {           // moving mass and plotting
			double t = (double)it/20.0;
			xMass = it + 100;
			yMass = 150 + (int)((y0-150)*Math.cos((double)(omega*t)));
			if (theColor == 1) g.setColor(Color.red);
			if (theColor == 2) g.setColor(Color.blue);
			if (theColor == 3) g.setColor(Color.green);
			if (theColor == 4) g.setColor(Color.cyan);
			if (theColor == 5) g.setColor(Color.magenta);
			if (it > 0) g.drawLine(xMass,yMass,xMold,yMold);
			xMold = xMass;
			yMold = yMass;
			ytop = yMass - 10;
			it++;
		}
		if (it == 400) a.myGo = false;
		drawMass(g);
		drawSpring(9,ytop-1,10,g);
		drawSpring(9,ytop,11,g);
	}
		
	public boolean handleEvent(Event evt){
		if (evt.target == this && evt.id == Event.MOUSE_DOWN) {
			osc_MouseDown(evt);
			return true;
		}
		if (evt.target == this && evt.id == Event.MOUSE_DRAG) {
			osc_MouseDrag(evt);
			return true;
		}
		if (evt.target == this && evt.id == Event.MOUSE_UP) {
			osc_MouseUp(evt);
			return true;
		}
		return false;
	}
	
	void osc_MouseDrag(Event event) {
		if (inTow) {
			yMass = event.y - dy;
			y0 = yMass;
			ytop = yMass - 10;
			repaint();
			it = 0;
		}
	}

	void osc_MouseDown(Event event) {
		dy = event.y - yMass;
		if (event.x < 50 && (int)Math.abs(dy) < 15) {
			inTow = true;
			a.myGo = false;
		}
	}

	void osc_MouseUp(Event event) {
		inTow = false;
	}
}