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package javafx.scene.control.cell;

import javafx.beans.property.BooleanProperty;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.beans.value.ObservableValue;
import javafx.geometry.Pos;
import javafx.scene.control.CheckBox;
import javafx.scene.control.ContentDisplay;
import javafx.scene.control.ListCell;
import javafx.scene.control.ListView;
import javafx.util.Callback;
import javafx.util.StringConverter;

/**
 * A class containing a {@link ListCell} implementation that draws a
 * {@link CheckBox} node inside the cell, optionally with a label to indicate
 * what the checkbox represents.
 *
 * <p>The CheckBoxListCell is rendered with a CheckBox on the left-hand side of
 * the {@link ListView}, and the text related to the list item taking up all
 * remaining horizontal space.
 *
 * <p>To construct an instance of this class, it is necessary to provide a
 * {@link Callback} that, given an object of type T, will return a
 * {@code ObservableValue<Boolean>} that represents whether the given item is
 * selected or not. This ObservableValue will be bound bidirectionally (meaning
 * that the CheckBox in the cell will set/unset this property based on user
 * interactions, and the CheckBox will reflect the state of the
 * ObservableValue<Boolean>, if it changes externally).
 *
 * <p>Note that the CheckBoxListCell renders the CheckBox 'live', meaning that
 * the CheckBox is always interactive and can be directly toggled by the user.
 * This means that it is not necessary that the cell enter its
 * {@link #editingProperty() editing state} (usually by the user double-clicking
 * on the cell). A side-effect of this is that the usual editing callbacks
 * (such as {@link javafx.scene.control.ListView#onEditCommitProperty() on edit commit})
 * will <strong>not</strong> be called. If you want to be notified of changes,
 * it is recommended to directly observe the boolean properties that are
 * manipulated by the CheckBox.</p>
 *
 * @see CheckBox
 * @see ListCell
 * @param <T> The type of the elements contained within the ListView.
 * @since JavaFX 2.2
 */
public class CheckBoxListCell<T> extends ListCell<T> {

    /***************************************************************************
     *                                                                         *
     * Static cell factories                                                   *
     *                                                                         *
     **************************************************************************/

    /**
     * Creates a cell factory for use in ListView controls. When used in a
     * ListView, the {@link CheckBoxListCell} is rendered with a CheckBox on the
     * left-hand side of the ListView, with the text related to the list item
     * taking up all remaining horizontal space.
     *
     * @param <T> The type of the elements contained within the ListView.
     * @param getSelectedProperty A {@link Callback} that, given an object of
     *      type T (which is a value taken out of the
     *      {@code ListView<T>.items} list),
     *      will return an {@code ObservableValue<Boolean>} that represents
     *      whether the given item is selected or not. This ObservableValue will
     *      be bound bidirectionally (meaning that the CheckBox in the cell will
     *      set/unset this property based on user interactions, and the CheckBox
     *      will reflect the state of the ObservableValue, if it changes
     *      externally).
     * @return A {@link Callback} that will return a ListCell that is able to
     *      work on the type of element contained within the ListView items list.
     */
    public static <T> Callback<ListView<T>, ListCell<T>> forListView(
            final Callback<T, ObservableValue<Boolean>> getSelectedProperty) {
        return forListView(getSelectedProperty, CellUtils.<T>defaultStringConverter());
    }

    /**
     * Creates a cell factory for use in ListView controls. When used in a
     * ListView, the {@link CheckBoxListCell} is rendered with a CheckBox on the
     * left-hand side of the ListView, with the text related to the list item
     * taking up all remaining horizontal space.
     *
     * @param <T> The type of the elements contained within the ListView.
     * @param getSelectedProperty A {@link Callback} that, given an object
     *      of type T (which is a value taken out of the
     *      {@code ListView<T>.items} list),
     *      will return an {@code ObservableValue<Boolean>} that represents
     *      whether the given item is selected or not. This ObservableValue will
     *      be bound bidirectionally (meaning that the CheckBox in the cell will
     *      set/unset this property based on user interactions, and the CheckBox
     *      will reflect the state of the ObservableValue, if it changes
     *      externally).
     * @param converter A StringConverter that, give an object of type T, will
     *      return a String that can be used to represent the object visually.
     * @return A {@link Callback} that will return a ListCell that is able to
     *      work on the type of element contained within the ListView.
     */
    public static <T> Callback<ListView<T>, ListCell<T>> forListView(
            final Callback<T, ObservableValue<Boolean>> getSelectedProperty,
            final StringConverter<T> converter) {
        return list -> new CheckBoxListCell<T>(getSelectedProperty, converter);
    }

    /***************************************************************************
     *                                                                         *
     * Fields                                                                  *
     *                                                                         *
     **************************************************************************/

    private final CheckBox checkBox;

    private ObservableValue<Boolean> booleanProperty;



    /***************************************************************************
     *                                                                         *
     * Constructors                                                            *
     *                                                                         *
     **************************************************************************/

    /**
     * Creates a default CheckBoxListCell.
     */
    public CheckBoxListCell() {
        this(null);
    }

    /**
     * Creates a default CheckBoxListCell.
     *
     * @param getSelectedProperty A {@link Callback} that will return an
     *      {@code ObservableValue<Boolean>} given an item from the ListView.
     */
    public CheckBoxListCell(
            final Callback<T, ObservableValue<Boolean>> getSelectedProperty) {
        this(getSelectedProperty, CellUtils.<T>defaultStringConverter());
    }

    /**
     * Creates a CheckBoxListCell with a custom string converter.
     *
     * @param getSelectedProperty A {@link Callback} that will return an
     *      {@code ObservableValue<Boolean>} given an item from the ListView.
     * @param converter A StringConverter that, given an object of type T, will
     *      return a String that can be used to represent the object visually.
     */
    public CheckBoxListCell(
            final Callback<T, ObservableValue<Boolean>> getSelectedProperty,
            final StringConverter<T> converter) {
        this.getStyleClass().add("check-box-list-cell");
        setSelectedStateCallback(getSelectedProperty);
        setConverter(converter);

        this.checkBox = new CheckBox();

        setAlignment(Pos.CENTER_LEFT);
        setContentDisplay(ContentDisplay.LEFT);

        // by default the graphic is null until the cell stops being empty
        setGraphic(null);
    }


    /***************************************************************************
     *                                                                         *
     * Properties                                                              *
     *                                                                         *
     **************************************************************************/

    // --- converter
    private ObjectProperty<StringConverter<T>> converter =
            new SimpleObjectProperty<StringConverter<T>>(this, "converter");

    /**
     * The {@link StringConverter} property.
     */
    public final ObjectProperty<StringConverter<T>> converterProperty() {
        return converter;
    }

    /**
     * Sets the {@link StringConverter} to be used in this cell.
     */
    public final void setConverter(StringConverter<T> value) {
        converterProperty().set(value);
    }

    /**
     * Returns the {@link StringConverter} used in this cell.
     */
    public final StringConverter<T> getConverter() {
        return converterProperty().get();
    }


    // --- selected state callback property
    private ObjectProperty<Callback<T, ObservableValue<Boolean>>>
            selectedStateCallback =
            new SimpleObjectProperty<Callback<T, ObservableValue<Boolean>>>(
            this, "selectedStateCallback");

    /**
     * Property representing the {@link Callback} that is bound to by the
     * CheckBox shown on screen.
     */
    public final ObjectProperty<Callback<T, ObservableValue<Boolean>>> selectedStateCallbackProperty() {
        return selectedStateCallback;
    }

    /**
     * Sets the {@link Callback} that is bound to by the CheckBox shown on screen.
     */
    public final void setSelectedStateCallback(Callback<T, ObservableValue<Boolean>> value) {
        selectedStateCallbackProperty().set(value);
    }

    /**
     * Returns the {@link Callback} that is bound to by the CheckBox shown on screen.
     */
    public final Callback<T, ObservableValue<Boolean>> getSelectedStateCallback() {
        return selectedStateCallbackProperty().get();
    }



    /***************************************************************************
     *                                                                         *
     * Public API                                                              *
     *                                                                         *
     **************************************************************************/

    /** {@inheritDoc} */
    @Override public void updateItem(T item, boolean empty) {
        super.updateItem(item, empty);

        if (! empty) {
            StringConverter<T> c = getConverter();
            Callback<T, ObservableValue<Boolean>> callback = getSelectedStateCallback();
            if (callback == null) {
                throw new NullPointerException(
                        "The CheckBoxListCell selectedStateCallbackProperty can not be null");
            }

            setGraphic(checkBox);
            setText(c != null ? c.toString(item) : (item == null ? "" : item.toString()));

            if (booleanProperty != null) {
                checkBox.selectedProperty().unbindBidirectional((BooleanProperty)booleanProperty);
            }
            booleanProperty = callback.call(item);
            if (booleanProperty != null) {
                checkBox.selectedProperty().bindBidirectional((BooleanProperty)booleanProperty);
            }
        } else {
            setGraphic(null);
            setText(null);
        }
    }
}
