//FileOrganizer.java

import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;
import java.awt.Color;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class FileOrganizer
    extends JFrame
    implements ActionListener
{
    public static final int WIDTH = 400;
    public static final int HEIGHT = 300;
    public static final int NUMBER_OF_CHAR = 30;
    private JTextField fileNameField;
    private JTextField firstLineField;

    public FileOrganizer()
    {
        setSize(WIDTH, HEIGHT);
        WindowDestroyer listener = new WindowDestroyer();
        addWindowListener(listener);

        Container contentPane = getContentPane();
        contentPane.setLayout(new FlowLayout());

        JButton showButton = new JButton("Show first line");
        showButton.addActionListener(this);
        contentPane.add(showButton);

        JButton removeButton = new JButton("Remove file");
        removeButton.addActionListener(this);
        contentPane.add(removeButton);

        JButton resetButton = new JButton("Reset");
        resetButton.addActionListener(this);
        contentPane.add(resetButton);

        fileNameField = new JTextField(NUMBER_OF_CHAR);
        contentPane.add(fileNameField);

        fileNameField.setText("Enter file name here.");
        firstLineField = new JTextField(NUMBER_OF_CHAR);
        contentPane.add(firstLineField);
    }

    public void actionPerformed
    (
        ActionEvent e
    )
    {
        String actionCommand = e.getActionCommand();
        if (actionCommand.equals("Show first line"))
            showFirstLine();
        else if (actionCommand.equals("Remove file"))
            removeFile();
        else if (actionCommand.equals("Reset"))
            resetFields();
        else
            firstLineField.setText("Unexpected error.");
    }

    private void showFirstLine()
    {
        Scanner fileInput = null;
        String fileName = fileNameField.getText();
        File fileObject = new File(fileName);

        if (!fileObject.exists())
            firstLineField.setText("No such file");
        else if (!fileObject.canRead())
            firstLineField.setText("That file is not readable.");
        else
        {
            try
            {
                fileInput = new Scanner(fileObject);
            }
            catch (FileNotFoundException e)
            {
                firstLineField.setText("Error opening the file " + fileName);
            }
            String firstLine = fileInput.nextLine();
            firstLineField.setText(firstLine);
            fileInput.close();
        }
    }

    private void resetFields()
    {
        fileNameField.setText("Enter file name here.");
        firstLineField.setText("");
    }

    private void removeFile()
    {
        Scanner fileInput = null;
        String firstLine;
        String fileName = fileNameField.getText();
        File fileObject = new File(fileName);

        if (!fileObject.exists())
            firstLineField.setText("No such file");
        else if (!fileObject.canWrite())
            firstLineField.setText("Permission denied.");
        else
        {
            if (fileObject.delete())
                firstLineField.setText("File deleted.");
            else
                firstLineField.setText("Could not delete file.");
        }
    }

    public static void main(String[] args)
    {
        FileOrganizer gui = new FileOrganizer();
        gui.setVisible(true);
    }
}