import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;

public class DiskWaste extends Panel
                    implements ActionListener, ItemListener {

// GUI elements
protected TextArea reportScreen;
protected Choice blockSizeChoice;
protected Button resetButton;

// statistics
protected int  numFiles        = 0;
protected long effectivelyUsed = 0;
protected long allocatedUsed   = 0;

protected int blockSizes[] = {512, 1024, 2048, 4096, 8192, 16384, 32768, 65536};
protected int blockSize, blockMask;

protected boolean newRun;

//-------------------------------------------------------------------
// DiskWaste constructor
//-------------------------------------------------------------------
public DiskWaste() {
	Label lbl = new Label("Disk Block Size:");

	blockSizeChoice = buildChoiceFromIntList(blockSizes);
	blockSizeChoice.addItemListener(this);

	resetButton = new Button("Reset Stats");
	resetButton.addActionListener(this);

	Panel controlPanel = new Panel();
	controlPanel.add(lbl);
	controlPanel.add(blockSizeChoice);
	controlPanel.add(resetButton);

	reportScreen = new TextArea("", 10, 80, TextArea.SCROLLBARS_NONE);
	reportScreen.setSize(300,200);
	reportScreen.setFont(new Font("Courier", Font.PLAIN, 12));

	setLayout(new BorderLayout());

	add("Center", reportScreen);
	add("South", controlPanel);

	itemStateChanged(null);		// force setting of block size & mask
	newRun = true;
}
//-------------------------------------------------------------------
// Utility function to create a Choice from a list of integers
//-------------------------------------------------------------------
public static Choice buildChoiceFromIntList(int[] list) {
Choice choice = new Choice();

	for (int i=0; i < list.length; i++) {
		choice.add( String.valueOf(list[i]) );
	}
	return choice;
}
//-------------------------------------------------------------------
// Reset statistics
//-------------------------------------------------------------------
protected void resetStats() {

	numFiles        = 0;
	effectivelyUsed = 0;
	allocatedUsed   = 0;

	// wipe report screen
	reportScreen.setText("");
}
//-------------------------------------------------------------------
// ActionListener interface method
//-------------------------------------------------------------------
public void actionPerformed(ActionEvent actionEvent) {

	if ( actionEvent instanceof FilenameActionEvent ) {
		String filename = ((FilenameActionEvent) actionEvent).getFilename();
		accumulateStats(filename);
	} else {
		Object source = actionEvent.getSource();
		if ( source instanceof Button ) {
			if ( source == resetButton ) {
				resetStats();
			}
		}
	}
}
//-------------------------------------------------------------------
// Given a filename, locate file and calc real and imaginary resource usage
//-------------------------------------------------------------------
protected void accumulateStats(String filename) {
File file;
long bytes;

	if ( filename == null ) {
		produceDiskUsageReport();
		newRun = true;
		return;
	}

	if ( newRun ) {
		resetStats();
		reportScreen.setText("Scanning.. please wait.");
		newRun = false;
	}

	numFiles++;

	file = new File(filename);
	bytes = file.length();			// what is this file's length ?

	effectivelyUsed += bytes;

	// calculate how many bytes were actually allocated to store them
	bytes = (bytes + blockSize) & blockMask;
    allocatedUsed += bytes;
}
//-------------------------------------------------------------------
// Using the accumulated statistics, produce a report of how much disk
// space is wasted.
//-------------------------------------------------------------------
protected void produceDiskUsageReport() {
StringBuffer report = new StringBuffer();

    float wastage = 100.0F - 100.0F * (effectivelyUsed) / (float)(allocatedUsed);

    report.append("DiskWaste report:\n");
    report.append("-----------------\n");
    report.append("\n");
    report.append("Total number of files     : " + numFiles        +"\n");
    report.append("File storage requirement  : " + effectivelyUsed +"\n");
    report.append("Storage actually required : " + allocatedUsed   +"\n");
    report.append("Wastage : " + wastage + "%\n" );
    report.append("\n");

    if (wastage < 5.0F) {
        report.append("That's not bad at all.");
    } else
    if (wastage < 15.0F) {
        report.append("A bit of wastage there..");
    } else
    if (wastage < 33.3F) {
        report.append("That's a lot of wasted hard disk space, don't you think?");
    } else
    if (wastage < 50.0F) {
        report.append("Wow! More than a third of space totally wasted.");
    } else
    if (wastage < 75.0F) {
        report.append("Incredible! Over half of your disk is being wasted!");
    } else {
        report.append(
"Hey man, you've got a problem here. More than three quarters of your disk is being wasted.");
    }
	report.append("\n");
	reportScreen.setText(report.toString());
}
//-------------------------------------------------------------------
// ItemListener interface method
// This is where new disk block size selections arrive. Record selection.
//-------------------------------------------------------------------
public void itemStateChanged(ItemEvent itemEvent) {

	int selectedSize = blockSizeChoice.getSelectedIndex();
    blockSize = blockSizes[ selectedSize ];

    // calculate filesize rounding function (using AND)
    blockMask = ~(blockSize-1);
}
//-------------------------------------------------------------------
// Self-Test code
//-------------------------------------------------------------------
public static void main (String[] args) {

Frame window = new Frame("DiskWaste");
DirLister dirLister = new DirLister();
DiskWaste diskWaste = new DiskWaste();

	window.add("Center", diskWaste);
	window.add("South", dirLister);
	dirLister.addActionListener(diskWaste);
	window.pack();
	window.setVisible(true);
}
} // End of Class DiskWaste