import java.awt.*;
import java.applet.*;
import java.io.*;
import java.net.*;
import java.awt.event.*;


public class localFileWrite extends Applet implements ActionListener {

Button button;
boolean macOS;
boolean windowsOS;
String userHome;
URL rootOnClientURL;
String reportString;
	
public void init()
{
	setBackground(new Color(255, 240, 200));
	button = new Button("Write file");  // file creation doesn't work from init, so a button and actionPerformed are used	
	button.addActionListener(this);
	add(button);	
	macOS = (System.getProperty("os.name").startsWith("Mac"));
	windowsOS = (System.getProperty("os.name").startsWith("Win"));
	userHome = System.getProperty("user.home");
	try
	{
		if (macOS) rootOnClientURL = new URL("file", "", "//" + System.getProperty("user.home") + "/");
		else if (windowsOS) rootOnClientURL = new URL("file:/" + userHome.replace('\\', '/')  + "/AppData/LocalLow/");
	}
	catch (Exception e)
	{
		System.out.println("Couldn't form URL");
		rootOnClientURL = null;
	}
}

public void actionPerformed(ActionEvent ae)
{
	if (ae.getSource() == button) 
	{
		try
		{
			String fileString = new URL(rootOnClientURL + "localFile.txt").getFile();
			fileString = getLocalFileForm(fileString);
			FileOutputStream fos = 	new FileOutputStream(fileString);  
			BufferedOutputStream bos = new BufferedOutputStream(fos, 32768);
			DataOutputStream dos = new DataOutputStream(bos);
			dos.writeUTF("Test file contents");
			dos.close();
			bos.close();
			fos.close();
			reportString = "Writing a local file worked.";
		}
		catch (Exception e)
		{
			reportString = "Writing a local file didn't work.  The Exception is: " + e.getMessage();
		}
		repaint();
	}
}

final String getLocalFileForm(String string)
{
	if (!macOS) while (string.startsWith("/")) string = string.substring(1);
	string = string.replace ('/', File.separatorChar); 
	StringBuffer out = new StringBuffer(string.length());  
	for (int i=0; i<string.length(); i++)
	{
		char c = string.charAt(i);
		if (c == '+') out.append(' ');  // + is a space
		else if (c == '%')  // e.g. %20 is a space
		{
			int c1 = Character.digit(string.charAt(++i), 16);
			int c2 = Character.digit(string.charAt(++i), 16);
			out.append((char) (c1*16 + c2));
		}
		else out.append(c);
	}
	return (out.toString());
}

public void paint(Graphics g)
{
	g.drawString("rootOnClientURL = " + rootOnClientURL, 10, 40);
	g.drawString(reportString, 10, 70);
}
}  // END OF Class localFileWrite