//Here is my titration applet.  Eric Mechalke
//This program plots a tritration curve for a strong acid(HCl) being titrated with a strong base(NaOH).
// Two arrays are used to hold pH vs. volume data.
import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;
import java.awt.Graphics;
import java.awt.Color;

public class titration extends Applet implements ActionListener
{
	TextField textV=new TextField("   "); //Volume of HCl
	TextField textM=new TextField("   "); //molarity of HCL
	TextField textB=new TextField("   "); //molarity of NaOH

	Label labelY=new Label("Volume of HCl");
	Label labelA=new Label("Molarity of HCl");
	Label labelB=new Label("Molarity of NaOH");
	Button mybutton=new Button("Titrate");

	double V, M,BM;
	int beginX, beginY, endX, endY;
	double mypH[]=new double [100]; //Holds calculated pH values for plot
	double myVol[]=new double[100]; //Holds actual volume, in liters,for each point in the titrations(for molarity calc).
    boolean paintIt=false;
    double endpointx1, endpointx2, endpointy1, endpointy2;

	public void init()
	{
		textV.setText("25");
		textM.setText("0.1");
		textB.setText("0.1");
		add(labelY);
		add(textV);
		add(labelA);
		add(textM);
		add(labelB);
		add(textB);
		add(mybutton);
		mybutton.addActionListener(this);
	}
//====================================================================================================
	public void fillArray()
	{
		String textRead;
		String myV, myM, myC,myB;
		double  molA, molB, H_remaining, H_molarity, Fb, Vb, Vl;
		String backtoString;

		myV=textV.getText(); //Gets the volume of acid to be titrated
		myM=textM.getText(); //Gets the molarity of the acid to be titrated
		myB=textM.getText(); //Gets the molarity of the titrant(base).
		V=Double.parseDouble(myV);
		M=Double.parseDouble(myM);
		BM=Double.parseDouble(myB);
		Vl=V/1000; //Constant Initial volume in liter
		molA=(Vl*M); // Constant value Initial moles of H+ to titrate
		molB=1.2*molA;  //Constant value. Amount of base needed to titrate 120%
		Vb=molB/BM;     //Constant value. Volume of base to be added




		System.out.println("********************************************************************");
		for (int i=0; i<100; i++)
		{
			myVol[i]=Vl+Vb*((double)i/100.0); // Initial volume + fraction of total volume of base to add
			Fb=molB*((double)i/100.0);  // Fb is the fraction of moles base added
			H_remaining=molA-Fb; // H+ remaining after adding OH-

			if (H_remaining > 0) // Before equivalance point pH is calculate from pH= -log[H+]
				{
				 H_molarity= H_remaining/myVol[i]; // molarity, [H+], calc.
				 mypH[i]=-Math.log(H_molarity)/Math.log(10);
				 //System.out.println("pH ="+ mypH[i] + " here is the volume = "+ myVol[i]);
				}
			else
				{     // After equivalance point we are finding OH- molarity
			     H_molarity= -H_remaining/myVol[i];
			     mypH[i]=14.0 + Math.log(H_molarity)/Math.log(10); // pH=pKw-pOH
			    // System.out.println("PH ="+ mypH[i] + " here is the volume = "+ myVol[i]);
				}

		}
	}
//=============================================================================================================
	public void paint(Graphics screen)
	{

		beginX=50;
		beginY=50;
	    endX=500;
	    endY=300;
		setSize(600, 400);
		int x1=0;
		int y1=0;
		int x2=200;
		int y2=200;
		screen.setColor(Color.blue);
		screen.drawRect(beginX, beginY, endX, endY);
		//******************************
		//draw the xy chart:
		screen.setColor(Color.black);


		//******************************
	    screen.drawString("pH",10, 200);
	    int j=13;  //labels pH 13 to 1
				  String jbacktoString;

				  for (int i=21; i<=294; i=i+21) //d
		          {
					    jbacktoString = Integer.toString(j);
				  		screen.drawString(jbacktoString,35, 55+i);
				  		j=j-1;
		  		   }

	    screen.drawString("Volume NaOH Titrant",250, 395);
		//******************************

	//***************************


		double x,y,ml, transX, transY, oldTransX, oldTransY;
		transX=0;
		transY=0;
		oldTransX=0;
		oldTransY=0;
		screen.setColor(Color.blue);

		for (int yy=21; yy<294; yy=yy+21)
			screen.drawLine(50,(50+yy), 550, (50+yy)); // pH lines y-axis

        if(paintIt==true)
        {
		 for (int i=0; i<100; i++) //Loop to read array
			{
			 //x=0;

			transX =50.0+(500*((double)i/100.0));
			transY =350.0 -(21.0*mypH[i])-5;
			screen.setColor(Color.red);
			  if(oldTransX == 0.0)
			  	{
					System.out.println("No line to print with first data point");
					oldTransX=transX;
             		oldTransY=transY;
				}
			  else
			  	{
					screen.drawLine((int)oldTransX, (int)oldTransY, (int) transX, (int) transY);
					oldTransX=transX;
             		oldTransY=transY;
				}


			}
			screen.setColor(Color.black);
			screen.drawLine((int)endpointx1, (int)endpointy1, (int)endpointx2, (int)endpointy2);
			x=43.0+(500*(83.5/100.0));
			ml=(V*M)/BM;

			jbacktoString = Double.toString(ml);
			screen.drawString(jbacktoString, (int)x , 375);
			screen.drawString("end point.", (int)x , 395);

			paintIt=false;
		}

	}
//==================================================================================================================
	public void actionPerformed(ActionEvent event)
	{

		String mycaption=event.getActionCommand();
		fillArray();
		if (mycaption.equals("Titrate"))
		{
			String myV, myM, myB;
			double V, M, Vl, molB=0, molA=0, V_endpt;
			myV=textV.getText(); //Gets the volume of acid to be titrated
			myM=textM.getText(); //Gets the molarity of the acid to be titrated
			myB=textB.getText(); //Gets the molarity of the titrant(base).
			V=Double.parseDouble(myV);
			M=Double.parseDouble(myM);
			BM=Double.parseDouble(myB);
		    Vl=V/1000; //Constant Initial volume in liter
		    molB = molA;  //Constant value. Amount of base needed to titrate 120%
			V_endpt=molB/BM;     //Constant value. Volume of base to be added
			System.out.println("the endpoint volume = "+V_endpt);

			endpointx1=50.0+(500*(83.5/100.0));;
			endpointy1= 345;
			endpointx2=50.0+(500*(83.5/100.0));
			//endpointx2=50.0+(500*((double)V_endpt/100.0));
			endpointy2=355;

			paintIt=true;

		    repaint();  //calls the paint portion of our program to happen

		}

	}
}