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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
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package javafx.scene.control;

import javafx.scene.control.cell.CheckBoxTreeCell;
import javafx.beans.property.BooleanProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.beans.value.ChangeListener;
import javafx.event.Event;
import javafx.event.EventType;
import javafx.scene.Node;

/**
 * TreeItem subclass that adds support for being in selected, unselected, and
 * indeterminate states. This is useful when used in conjunction with a TreeView
 * which has a {@link CheckBoxTreeCell} installed.
 *
 * <p>A CheckBoxTreeItem can be {@link #independentProperty() independent} or
 * dependent. By default, CheckBoxTreeItem instances are dependent, which means
 * that any changes to the selection state of a TreeItem will have an impact on
 * parent and children CheckBoxTreeItem instances. If a CheckBoxTreeItem is
 * set to be independent, this means that any changes to that CheckBoxTreeItem
 * will not directly impact the state of parent and children CheckBoxTreeItem
 * instances.
 *
 * <p>The {@link #indeterminateProperty() indeterminate} property is used to
 * represent the same concept as that in {@link CheckBox#indeterminateProperty()},
 * namely, that the CheckBox is neither selected or unselected. This is commonly
 * used inside a TreeView when some, but not all, of a branches children are
 * selected.
 *
 * <p>A simple example of using the CheckBoxTreeItem class, in conjunction with
 * {@link CheckBoxTreeCell} is shown below:
 *
 * <pre><code>// create the tree model
 * CheckBoxTreeItem&lt;String&gt; jonathanGiles = new CheckBoxTreeItem&lt;&gt;("Jonathan");
 * CheckBoxTreeItem&lt;String&gt; juliaGiles = new CheckBoxTreeItem&lt;&gt;("Julia");
 * CheckBoxTreeItem&lt;String&gt; mattGiles = new CheckBoxTreeItem&lt;&gt;("Matt");
 * CheckBoxTreeItem&lt;String&gt; sueGiles = new CheckBoxTreeItem&lt;&gt;("Sue");
 * CheckBoxTreeItem&lt;String&gt; ianGiles = new CheckBoxTreeItem&lt;&gt;("Ian");
 *
 * CheckBoxTreeItem&lt;String&gt; gilesFamily = new CheckBoxTreeItem&lt;&gt;("Giles Family");
 * gilesFamily.setExpanded(true);
 * gilesFamily.getChildren().addAll(jonathanGiles, juliaGiles, mattGiles, sueGiles, ianGiles);
 *
 * // create the treeView
 * final TreeView&lt;String&gt; treeView = new TreeView&lt;&gt;();
 * treeView.setRoot(gilesFamily);
 *
 * // set the cell factory
 * treeView.setCellFactory(CheckBoxTreeCell.&lt;String&gt;forTreeView());</code></pre>
 *
 * <img src="doc-files/CheckBoxTreeItem.png" alt="Image of the CheckBoxTreeItem control">
 *
 * @param <T> The type of the value contained within the TreeItem
 * @see CheckBoxTreeCell
 * @see TreeItem
 * @see CheckBox
 * @since JavaFX 2.2
 */
// TODO the TreeModificationEvent doesn't actually bubble in the same way as
// TreeItem - it just looks that way as the 'bubbling' is done via changing the
// state of all parent items.
public class CheckBoxTreeItem<T> extends TreeItem<T> {

    /**
     * An EventType used when the CheckBoxTreeItem selection / indeterminate
     * state changes. To use this, it is recommended that you use code along the
     * lines of the following:
     *
     *<pre>
     * {@code
     * child1.addEventHandler(CheckBoxTreeItem.<String>checkBoxSelectionChangedEvent(), new EventHandler<TreeModificationEvent<String>>() {
     *     public void handle(TreeModificationEvent<String> event) {
     *          ...
     *     }
     * });}
     * </pre>
     *
     * @param <T> The type of the value contained within the TreeItem.
     * @return the EventType used when the CheckBoxTreeItem selection / indeterminate
     * state changes
     */
    @SuppressWarnings("unchecked")
    public static <T> EventType<TreeModificationEvent<T>> checkBoxSelectionChangedEvent() {
        return (EventType<TreeModificationEvent<T>>) CHECK_BOX_SELECTION_CHANGED_EVENT;
    }
    private static final EventType<? extends Event> CHECK_BOX_SELECTION_CHANGED_EVENT
            = new EventType<Event>(TreeModificationEvent.ANY, "checkBoxSelectionChangedEvent");

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

    /**
     * Creates an empty CheckBoxTreeItem.
     */
    public CheckBoxTreeItem() {
        this(null);
    }

    /**
     * Creates a CheckBoxTreeItem with the value property set to the provided
     * object.
     *
     * @param value The object to be stored as the value of this TreeItem.
     */
    public CheckBoxTreeItem(T value) {
        this(value, null, false);
    }

    /**
     * Creates a CheckBoxTreeItem with the value property set to the provided
     * object, and the graphic set to the provided Node.
     *
     * @param value The object to be stored as the value of this CheckBoxTreeItem.
     * @param graphic The Node to show in the TreeView next to this CheckBoxTreeItem.
     */
    public CheckBoxTreeItem(T value, Node graphic) {
        this(value, graphic, false);
    }

    /**
     * Creates a CheckBoxTreeItem with the value property set to the provided
     * object, the graphic set to the provided Node, and the initial state
     * of the {@link #selectedProperty()} set to the provided boolean value.
     *
     * @param value The object to be stored as the value of this CheckBoxTreeItem.
     * @param graphic The Node to show in the TreeView next to this CheckBoxTreeItem.
     * @param selected The initial value of the
     *            {@link #selectedProperty() selected} property.
     */
    public CheckBoxTreeItem(T value, Node graphic, boolean selected) {
        this(value, graphic, selected, false);
    }

    /**
     * Creates a CheckBoxTreeItem with the value property set to the provided
     * object, the graphic set to the provided Node, the initial state
     * of the {@link #selectedProperty()} set to the provided boolean value, and
     * the initial state of the {@link #independentProperty() independent}
     * property to the provided boolean value.
     *
     * @param value The object to be stored as the value of this CheckBoxTreeItem.
     * @param graphic The Node to show in the TreeView next to this CheckBoxTreeItem.
     * @param selected The initial value of the
     *            {@link #selectedProperty() selected} property.
     * @param independent The initial value of the
     *            {@link #independentProperty() independent} property
     */
    public CheckBoxTreeItem(T value, Node graphic, boolean selected, boolean independent) {
        super(value, graphic);
        setSelected(selected);
        setIndependent(independent);

        selectedProperty().addListener(stateChangeListener);
        indeterminateProperty().addListener(stateChangeListener);
    }



    /* *************************************************************************
     *                                                                         *
     * Callbacks                                                               *
     *                                                                         *
     **************************************************************************/
    private final ChangeListener<Boolean> stateChangeListener = (ov, oldVal, newVal) -> {
        updateState();
    };


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

    // --- Selected
    private final BooleanProperty selected = new SimpleBooleanProperty(this, "selected", false) {
        @Override protected void invalidated() {
            super.invalidated();
            fireEvent(CheckBoxTreeItem.this, true);
        }
    };

    /**
     * Sets the selected state of this CheckBoxTreeItem.
     * @param value the selected state of this CheckBoxTreeItem
     */
    public final void setSelected(boolean value) { selectedProperty().setValue(value); }

    /**
     * Returns the selected state of this CheckBoxTreeItem.
     * @return true if CheckBoxTreeItem is selected
     */
    public final boolean isSelected() { return selected.getValue(); }

    /**
     * A {@link BooleanProperty} used to represent the selected state of this CheckBoxTreeItem.
     * @return the selected state property of this CheckBoxTreeItem
     */
    public final BooleanProperty selectedProperty() { return selected; }


    // --- Indeterminate
    private final BooleanProperty indeterminate = new SimpleBooleanProperty(this, "indeterminate", false) {
        @Override protected void invalidated() {
            super.invalidated();
            fireEvent(CheckBoxTreeItem.this, false);
        }
    };

    /**
     * Sets the indeterminate state of this CheckBoxTreeItem.
     * @param value the indeterminate state of this CheckBoxTreeItem
     */
    public final void setIndeterminate(boolean value) { indeterminateProperty().setValue(value); }

    /**
     * Returns the indeterminate state of this CheckBoxTreeItem.
     * @return true if CheckBoxTreeItem is indeterminate state
     */
    public final boolean isIndeterminate() { return indeterminate.getValue(); }

    /**
     * A {@link BooleanProperty} used to represent the indeterminate state of this CheckBoxTreeItem.
     * @return the indeterminate state property of this CheckBoxTreeItem
     */
    public final BooleanProperty indeterminateProperty() { return indeterminate; }


    // --- Independent
    /**
     * A {@link BooleanProperty} used to represent the independent state of this CheckBoxTreeItem.
     * The independent state is used to represent whether changes to a single
     * CheckBoxTreeItem should influence the state of its parent and children.
     *
     * <p>By default, the independent property is false, which means that when
     * a CheckBoxTreeItem has state changes to the selected or indeterminate
     * properties, the state of related CheckBoxTreeItems will possibly be changed.
     * If the independent property is set to true, the state of related CheckBoxTreeItems
     * will <b>never</b> change.
     * @return the independent state property of this CheckBoxTreeItem
     */
    public final BooleanProperty independentProperty() { return independent; }
    private final BooleanProperty independent = new SimpleBooleanProperty(this, "independent", false);
    public final void setIndependent(boolean value) { independentProperty().setValue(value); }
    public final boolean isIndependent() { return independent.getValue(); }



    /* *************************************************************************
     *                                                                         *
     * Private Implementation                                                  *
     *                                                                         *
     **************************************************************************/

    private static boolean updateLock = false;

    private void updateState() {
        if (isIndependent()) return;

        boolean firstLock = ! updateLock;

        // toggle parent (recursively up to root)
        updateLock = true;
        updateUpwards();

        if (firstLock) updateLock = false;

        // toggle children
        if (updateLock) return;
        updateDownwards();
    }

    private void updateUpwards() {
        if (! (getParent() instanceof CheckBoxTreeItem)) return;

        CheckBoxTreeItem<?> parent = (CheckBoxTreeItem<?>) getParent();
        int selectCount = 0;
        int indeterminateCount = 0;
        for (TreeItem<?> child : parent.getChildren()) {
            if (! (child instanceof CheckBoxTreeItem)) continue;

            CheckBoxTreeItem<?> cbti = (CheckBoxTreeItem<?>) child;

            selectCount += cbti.isSelected() && ! cbti.isIndeterminate() ? 1 : 0;
            indeterminateCount += cbti.isIndeterminate() ? 1 : 0;
        }

        if (selectCount == parent.getChildren().size()) {
            parent.setSelected(true);
            parent.setIndeterminate(false);
        } else if (selectCount == 0 && indeterminateCount == 0) {
            parent.setSelected(false);
            parent.setIndeterminate(false);
        } else {
            parent.setIndeterminate(true);
        }
    }

    private void updateDownwards() {
        // If this node is not a leaf, we also put all
        // children into the same state as this branch
        if (! isLeaf()) {
            for (TreeItem<T> child : getChildren()) {
                if (child instanceof CheckBoxTreeItem) {
                    CheckBoxTreeItem<T> cbti = ((CheckBoxTreeItem<T>) child);
                    cbti.setSelected(isSelected());
                }
            }
        }
    }

    private void fireEvent(CheckBoxTreeItem<T> item, boolean selectionChanged) {
        Event evt = new CheckBoxTreeItem.TreeModificationEvent<T>(CHECK_BOX_SELECTION_CHANGED_EVENT, item, selectionChanged);
        Event.fireEvent(this, evt);
    }


    /**
     * A TreeModificationEvent class that works in a similar vein to the
     * {@link javafx.scene.control.TreeItem.TreeModificationEvent} class, in that
     * this event will bubble up the CheckBoxTreeItem hierarchy, until the parent
     * node is null.
     *
     * @param <T> The type of the value contained within the
     *      {@link CheckBoxTreeItem#valueProperty() value} property.
     * @since JavaFX 2.2
     */
    public static class TreeModificationEvent<T> extends Event {
        private static final long serialVersionUID = -8445355590698862999L;

        private transient final CheckBoxTreeItem<T> treeItem;
        private final boolean selectionChanged;

        /**
         * Common supertype for all tree modification event types.
         */
        public static final EventType<Event> ANY =
                new EventType<Event> (Event.ANY, "TREE_MODIFICATION");

        /**
         * Creates a default TreeModificationEvent instance to represent the
         * change in selection/indeterminate states for the given CheckBoxTreeItem
         * instance.
         * @param eventType the eventType
         * @param treeItem the treeItem
         * @param selectionChanged represents whether the selection has changed
         */
        public TreeModificationEvent(EventType<? extends Event> eventType, CheckBoxTreeItem<T> treeItem, boolean selectionChanged) {
            super(eventType);
            this.treeItem = treeItem;
            this.selectionChanged = selectionChanged;
        }

        /**
         * Returns the CheckBoxTreeItem that this event occurred upon.
         * @return The CheckBoxTreeItem that this event occurred upon.
         */
        public CheckBoxTreeItem<T> getTreeItem() {
            return treeItem;
        }

        /**
         * Indicates the reason for this event is that the selection on the
         * CheckBoxTreeItem changed (as opposed to it becoming indeterminate).
         * @return has the CheckBoxTreeItem's selection changed
         */
        public boolean wasSelectionChanged() {
            return selectionChanged;
        }

        /**
         * Indicates the reason for this event is that the indeterminate
         * state on the CheckBoxTreeItem changed (as opposed to it becoming
         * selected or unselected).
         * @return has the CheckBoxTreeItem's indeterminate changed
         */
        public boolean wasIndeterminateChanged() {
            return ! selectionChanged;
        }
    }
}
