#format java
/**
 * MediatorPattern example
 * GUI Login
 */

import java.awt.*;
import java.awt.event.*;

interface Mediator {
    public abstract void createColleagues();
    public abstract void colleagueChanged(Colleague colleague);
}

interface Colleague {
    public abstract void setMediator(Mediator mediator);
    public abstract void setColleagueEnabled(boolean enabled);
}

class ColleagueButton extends Button implements Colleague {
    private Mediator mediator;
    public ColleagueButton(String caption) {
        super(caption);
    }
    public void setMediator(Mediator mediator) {
        this.mediator = mediator;
    }
    public void setColleagueEnabled(boolean enabled) {
        setEnabled(enabled);
    }
}

class ColleagueTextField extends TextField implements TextListener, Colleague {
    private Mediator mediator;
    public ColleagueTextField(String text, int columns) {
        super(text, columns);
    }
    public void setMediator(Mediator mediator) {
        this.mediator = mediator;
    }
    public void setColleagueEnabled(boolean enabled) {
        setEnabled(enabled);
        setBackground(enabled ? Color.white : Color.lightGray);
    }
    public void textValueChanged(TextEvent e) {
        mediator.colleagueChanged(this);
    }
}

class ColleagueCheckbox extends Checkbox implements ItemListener, Colleague {
    private Mediator mediator;
    public ColleagueCheckbox(String caption, 
                             CheckboxGroup group, boolean state) {
        super(caption, group, state);
    }
    public void setMediator(Mediator mediator) {
        this.mediator = mediator;
    }
    public void setColleagueEnabled(boolean enabled) {
        setEnabled(enabled);
    }
    public void itemStateChanged(ItemEvent e) {
        mediator.colleagueChanged(this);
    }
}

class LoginFrame extends Frame implements ActionListener, Mediator {
    private ColleagueCheckbox checkGuest;
    private ColleagueCheckbox checkLogin;
    private ColleagueTextField textUser;
    private ColleagueTextField textPass;
    private ColleagueButton buttonOk;
    private ColleagueButton buttonCancel;

    // Constructor: create Colleagues, position, display
    public LoginFrame(String title) {
        super(title);
        setBackground(Color.lightGray);
        setLayout(new GridLayout(4,2));

        // create and position
        createColleagues();
        add(checkGuest);
        add(checkLogin);
        add(new Label("Username:"));
        add(textUser);
        add(new Label("Password:"));
        add(textPass);
        add(buttonOk);
        add(buttonCancel);

        // enabled initial setting and display
        colleagueChanged(checkGuest);
        pack();
        show();
    }

    public void createColleagues() {
        CheckboxGroup g = new CheckboxGroup();
        checkGuest = new ColleagueCheckbox("Guest",g,true);
        checkLogin = new ColleagueCheckbox("Login",g,false);
        textUser = new ColleagueTextField("",10);
        textPass = new ColleagueTextField("",10);
        textPass.setEchoChar('*');
        buttonOk = new ColleagueButton("OK");
        buttonCancel = new ColleagueButton("Cancel");

        // Mediator setting
        checkGuest.setMediator(this);
        checkLogin.setMediator(this);
        textUser.setMediator(this);
        textPass.setMediator(this);
        buttonOk.setMediator(this);
        buttonCancel.setMediator(this);

        // Listener setting
        checkGuest.addItemListener(checkGuest);
        checkLogin.addItemListener(checkLogin);
        textUser.addTextListener(textUser);
        textPass.addTextListener(textPass);
        buttonOk.addActionListener(this);
        buttonCancel.addActionListener(this);
    }

    public void colleagueChanged(Colleague c) {
        if(c == checkGuest || c == checkLogin) {
            if(checkGuest.getState()) {   // Guest mode
                textUser.setColleagueEnabled(false);
                textPass.setColleagueEnabled(false);
                buttonOk.setColleagueEnabled(true);
            } else {
                textUser.setColleagueEnabled(true);
                userpassChanged();
            } 
        } else if(c == textUser || c == textPass) {
            userpassChanged();
        } else {
            System.out.println("colleagueChanged:unknown colleague ="+c);
        }
    }

    private void userpassChanged() {
        if(textUser.getText().length() > 0) {
            textPass.setColleagueEnabled(true);
            if(textPass.getText().length() > 0) {
                buttonOk.setColleagueEnabled(true);
            } else {
                buttonOk.setColleagueEnabled(false);
            }
        } else {
            textPass.setColleagueEnabled(false);
            buttonOk.setColleagueEnabled(false);
        }
    }
    public void actionPerformed(ActionEvent e) {
        System.out.println(""+e);
        System.exit(0);
    }
}

public class MediatorGuiLogin {
    public static void main(String[] args) {
        new LoginFrame("Mediator Sample");
    }
}