ts3java/ts3-client/swing/src/main/java/com/ts3client/ui/ReasonDialog.java

package com.ts3client.ui;

import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JComponent;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.event.AncestorEvent;
import javax.swing.event.AncestorListener;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;
import java.awt.Component;
import java.awt.Dimension;

/**
 * Asks for the reason text that goes with a moderation action. The server caps
 * such messages, so the field refuses anything longer.
 */
final class ReasonDialog {

    /** The longest reason the protocol carries with a kick. */
    static final int KICK_REASON_LIMIT = 40;

    private ReasonDialog() {
    }

    /** @return the reason (possibly empty), or {@code null} when the dialog was cancelled */
    static String prompt(Component owner, String title, String message, int maxLength) {
        JTextField field = reasonField(maxLength);
        focusWhenShown(field);

        JPanel panel = new JPanel();
        panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
        panel.add(label(message));
        panel.add(field);

        int result = JOptionPane.showConfirmDialog(owner, panel, title,
                JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE);
        return result == JOptionPane.OK_OPTION ? field.getText().trim() : null;
    }

    static JTextField reasonField(int maxLength) {
        JTextField field = new JTextField(24);
        field.setDocument(new LimitedDocument(maxLength));
        field.setAlignmentX(Component.LEFT_ALIGNMENT);
        fixHeight(field);
        return field;
    }

    /** A left-aligned label with a little air below it, for use in a box layout. */
    static JLabel label(String text) {
        JLabel label = new JLabel(text);
        label.setAlignmentX(Component.LEFT_ALIGNMENT);
        label.setBorder(BorderFactory.createEmptyBorder(0, 0, 4, 0));
        return label;
    }

    /** Keeps a component from stretching taller than it needs in a box layout. */
    static void fixHeight(Component c) {
        c.setMaximumSize(new Dimension(Integer.MAX_VALUE, c.getPreferredSize().height));
    }

    /** Puts the caret in a field as soon as its dialog appears. */
    static void focusWhenShown(JComponent field) {
        field.addAncestorListener(new AncestorListener() {
            @Override
            public void ancestorAdded(AncestorEvent event) {
                field.requestFocusInWindow();
            }

            @Override
            public void ancestorRemoved(AncestorEvent event) {
            }

            @Override
            public void ancestorMoved(AncestorEvent event) {
            }
        });
    }

    /** A document that silently drops anything past its length limit. */
    private static final class LimitedDocument extends PlainDocument {

        private final int limit;

        LimitedDocument(int limit) {
            this.limit = limit;
        }

        @Override
        public void insertString(int offset, String text, AttributeSet attrs) throws BadLocationException {
            if (text == null) return;
            int room = limit - getLength();
            if (room <= 0) return;
            super.insertString(offset, text.length() > room ? text.substring(0, room) : text, attrs);
        }
    }
}