/*
    Archimedes experiment
 */

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

public class archi extends Applet {
    public MediaTracker tracker, trackerBg;
	public Image offScreenImage;
	public Image lWater, lAlcohol, theBack;
	public boolean copyRight = false, glasup = false, dragSlider = false;
	public boolean water = true;
	public int thex = 290, they = 115, xdist = 0;
	public double force = 2.0;
	public int substance = 1;  //  (1: titanium, or 2: tungsten)
	
	public void init() {
		super.init();		
		offScreenImage = createImage(500,360);

		//{{INIT_CONTROLS
		setLayout(null);
		resize(500,350);
		//}}
		
		trackerBg = new MediaTracker(this);
		theBack = this.getImage(getCodeBase(),"bg.jpg");
		trackerBg.addImage(theBack,0);
		try {
	    	trackerBg.waitForID(0);
		} catch (InterruptedException e) {
		}
		
		lWater = this.getImage(getCodeBase(),"glaspurple.jpg");
		trackerBg.addImage(lWater,0);
		try {
	    	trackerBg.waitForID(0);
		} catch (InterruptedException e) {
		}
		
		lAlcohol = this.getImage(getCodeBase(),"glasblue2.jpg");
		trackerBg.addImage(lAlcohol,0);
		try {
	    	trackerBg.waitForID(0);
		} catch (InterruptedException e) {
		}
		
		repaint();
	}

	public void update(Graphics g){
		Graphics offg = offScreenImage.getGraphics();
		paint(offg);
		g.drawImage(offScreenImage, 0, 0, this);
	}

	public void paint(Graphics g){
		g.setColor(Color.white);
		g.fillRect(0,0,500,350);
		g.drawImage(theBack,0,0,theBack.getWidth(this),theBack.getHeight(this),this);
		if (water) {
			if (glasup) {
				g.drawImage(lWater,34,140,lWater.getWidth(this),lWater.getHeight(this),this);
			} else {
				g.drawImage(lWater,34,235,lWater.getWidth(this),lWater.getHeight(this),this);
			}
		} else {
			if (glasup) {
				g.drawImage(lAlcohol,34,140,lAlcohol.getWidth(this),lAlcohol.getHeight(this),this);
			} else {
				g.drawImage(lAlcohol,34,235,lAlcohol.getWidth(this),lAlcohol.getHeight(this),this);
			}
		}
		
		// Physics section:
		double Volume = 75.8; // cm^3   =  assumed volume of object
		double rho_liquid = 1.0; // g/cm^3  if water
		if (!water) rho_liquid = 0.7;  // if alcohol
		double rho_metal = 4.54; // g/cm^3  if titanium
		if (substance == 2) rho_metal = 19.3;  // if tungsten
		double weight = 0.001 * rho_metal * Volume * 9.81;  // in N
		if (glasup) weight = weight - 0.001 * rho_liquid * Volume * 9.81;
		g.drawString("Weight = "+weight,200,30);
		
		g.setColor(Color.blue);
		double needleL = 23;
		double needleT = (weight - force) * Math.PI / 3.;
		if (needleT < -0.8*Math.PI) needleT = -0.8*Math.PI;
		if (needleT >  0.8*Math.PI) needleT =  0.8*Math.PI;
		int endx = 65 + (int)(needleL * Math.sin(needleT));
		int endy = 63 - (int)(needleL * Math.cos(needleT));
		g.drawLine(65,63,endx,endy);
		g.drawLine(64,63,endx-1,endy);
		g.drawLine(66,63,endx+1,endy);

		// sliding weight
		g.setColor(Color.black);
		g.fillRect(thex-15,they,31,21);
		g.setColor(Color.lightGray);
		g.fillRect(thex-2,they+1,5,19);
		g.setColor(Color.green);
		g.drawLine(thex,they+2,thex,they+17);
		
		// rope and object
		if (!glasup) {
			g.setColor(Color.black);
			g.fillOval(45,215,40,18);
			g.fillRect(45,209,40,15);
			g.setColor(Color.darkGray);
			g.fillOval(45,200,40,18);
		} else {
			g.setColor(Color.darkGray);
			g.fillOval(45,215,40,18);
			g.fillRect(45,209,40,15);
			g.setColor(Color.gray);
			g.fillOval(45,200,40,18);
		}
		g.setFont(new Font("Helvetica", Font.BOLD, 14));
		g.setColor(Color.red);
		if (glasup) g.setColor(Color.pink);
		g.drawString(""+substance,62,230);
		
		g.setColor(Color.gray);
		g.fillRect(64,136,3,73);
		if (glasup) {
			g.setColor(Color.lightGray);
			g.fillRect(64,186,3,23);
		}

		// labels:  active ones are red, passive are gray
		g.setFont(new Font("Helvetica", Font.BOLD, 14));
		
		if (glasup) {
			g.setColor(Color.red);
			g.drawString("Up",453,306);
			g.setColor(Color.black);
			g.drawString("Down",440,340);
		} else {
			g.setColor(Color.black);
			g.drawString("Up",453,306);
			g.setColor(Color.red);
			g.drawString("Down",440,340);
		}		
		if (water) {
			g.setColor(Color.red);
			g.drawString("Water",356,306);
			g.setColor(Color.black);
			g.drawString("Alcohol",356,340);
		} else {
			g.setColor(Color.black);
			g.drawString("Water",366,306);
			g.setColor(Color.red);
			g.drawString("Alcohol",352,340);
		}
		
		// select the substance labels
		g.setColor(Color.gray);
		g.fillOval(347,239,12,12);
		g.fillOval(347,259,12,12);
		g.setColor(Color.black);
		g.drawOval(347,239,12,12);
		g.drawOval(347,259,12,12);
		if (substance == 1) {
			g.setColor(Color.red);
			g.fillOval(349,241,9,9);
			g.drawString("Substance 1",375,250);
			g.setColor(Color.black);
			g.drawString("Substance 2",375,270);
		} else {
			g.setColor(Color.red);
			g.fillOval(349,261,9,9);
			g.drawString("Substance 2",375,270);
			g.setColor(Color.black);
			g.drawString("Substance 1",375,250);
		}
				
		g.setColor(Color.yellow);
		g.setFont(new Font("Helvetica", Font.BOLD, 18));
		g.drawString("F = "+outString(""+force,5)+" N",380,30);
				
		// copyright notice:
		if (copyRight) {
			g.setColor(Color.green);
			g.fillRect(100,100,240,70);
			g.setColor(Color.white);
			g.setFont(new Font("Helvetica", Font.PLAIN, 18));
			g.drawString("This applet was written by:",110,120);
			g.drawString("Wolfgang Bauer",110,140);
			g.drawString("Copyright: WB 1999",110,160);
		}
	}

	public boolean handleEvent(Event event) {
		if (event.id == Event.KEY_PRESS){
			String thePressedKey = ""+(char)event.key;
			if (thePressedKey.equalsIgnoreCase("w")) {
				copyRight = !copyRight;
	            repaint();
			}
		}
		if (event.key == Event.DOWN || event.key == Event.LEFT){
			if (event.shiftDown()){
				if (force > 0.0) force = force - 0.02;
				thex = (int)(10*force+270.5);
			} else {
				if (thex > 270) thex--;
				force = 0.1 * (thex - 270);
			}
			repaint();
		}
		if (event.key == Event.UP || event.key == Event.RIGHT){
			if (event.shiftDown()){
				force = force + 0.02;
				thex = (int)(10*force+270.5);
			} else {
				if (thex < 440) thex++;
				force = 0.1 * (thex - 270);
			}
			repaint();
		}

		if (event.target == this && event.id == Event.MOUSE_UP) {
			a_MouseUp(event);
			return true;
		}
		if (event.target == this && event.id == Event.MOUSE_DOWN) {
			a_MouseDown(event);
			return true;
		}
		if (event.target == this && event.id == Event.MOUSE_DRAG) {
			a_MouseDrag(event);
			return true;
		}
		return super.handleEvent(event);
	}

	public String outString(String inString, int l){    // returns the first l chars of string
		int ls = (int)Math.min(inString.length(),l);
		return inString.substring(0,ls);
	}

	void a_MouseDown(Event event) {
		int xx = event.x;
		int yy = event.y;
		xdist = xx-thex;
		if (Math.abs(xdist) < 10 && yy > they && yy < they + 22) {
			dragSlider = true;
		}
		repaint();
	}

	void a_MouseDrag(Event event) {
		int xx = event.x;
		int yy = event.y;
		if (dragSlider) thex = Math.min(440,Math.max(270,xx - xdist));
		force = 0.1 * (thex - 270);
		repaint();
	}

	void a_MouseUp(Event event) {
		int xx = event.x;
		int yy = event.y;
		dragSlider = false;
		if (xx > 345 && xx < 360) {
			if (yy > 237 && yy < 252) {
				substance = 1;
			} else if (yy > 257 && yy < 272) {
				substance = 2;
			}
		}
		if (xx > 423) {
			if (yy > 285 && yy < 316) glasup = true;
			if (yy > 319) glasup = false;
		} else if (xx > 347) {
			if (yy > 285 && yy < 316) water = true;
			if (yy > 319) water = false;
		}
		repaint();
	}

	//{{DECLARE_CONTROLS
	//}}
}