import java.awt.EventQueue;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JTextField;

public class AutoSuggest<E> extends JComboBox<E> {

    private final JComboBox<E> comboBox = this;
    private final JTextField textField = (JTextField) getEditor().getEditorComponent();
    private final List<String> suggestions = new LinkedList<>();
    private boolean hide_flag = false;

    public AutoSuggest() {
        super();

        setEditable(true);

        textField.addKeyListener(new KeyAdapter() {
            @Override
            public void keyTyped(KeyEvent e) {
                EventQueue.invokeLater(() -> {
                    String text = textField.getText();
                    if (text.length() == 0) {
                        comboBox.hidePopup();
                        setModel(new DefaultComboBoxModel(suggestions.toArray()), "");
                    } else {
                        DefaultComboBoxModel m = getSuggestedModel(suggestions, text);
                        if (m.getSize() == 0 || hide_flag) {
                            comboBox.hidePopup();
                            hide_flag = false;
                        } else {
                            setModel(m, text);
                            comboBox.showPopup();
                        }
                    }
                });
            }

            @Override
            public void keyPressed(KeyEvent e) {
                String text = textField.getText();
                int code = e.getKeyCode();
                switch (code) {
                    case KeyEvent.VK_ENTER:
                        if (!suggestions.contains(text)) {
                            suggestions.add(text);
                            Collections.sort(suggestions);
                            setModel(getSuggestedModel(suggestions, text), text);
                        }
                        hide_flag = true;
                        break;
                    case KeyEvent.VK_ESCAPE:
                        hide_flag = true;
                        break;
                    case KeyEvent.VK_RIGHT:
                        for (int i = 0; i < suggestions.size(); i++) {
                            String str = suggestions.get(i);
                            if (str.startsWith(text)) {
                                comboBox.setSelectedIndex(-1);
                                textField.setText(str);
                                return;
                            }
                        }
                        break;
                    default:
                        break;
                }
            }
        });

        setModel(new DefaultComboBoxModel(suggestions.toArray()), "");
    }

    public void update(Set<String> terms) {
        textField.setText("");

        suggestions.clear();
        suggestions.addAll(terms);

        setModel(new DefaultComboBoxModel(suggestions.toArray()), "");
    }

    private void setModel(DefaultComboBoxModel defaultComboBoxModel, String text) {
        comboBox.setModel(defaultComboBoxModel);
        comboBox.setSelectedIndex(-1);
        textField.setText(text);
    }

    private static DefaultComboBoxModel getSuggestedModel(List<String> list, String text) {
        DefaultComboBoxModel m = new DefaultComboBoxModel();
        list.stream().filter((s) -> (s.toLowerCase().startsWith(text.toLowerCase()))).forEach((s) -> {
            m.addElement(s);
        });
        return m;
    }

    public JTextField getTextField() {
        return textField;
    }

    public String getText() {
        return textField.getText();
    }

}