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package javafx.scene;

import com.sun.javafx.collections.TrackableObservableList;
import javafx.beans.property.BooleanProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.collections.ListChangeListener;
import javafx.collections.ObservableList;
import java.util.ArrayList;
import java.util.List;
import java.util.ListIterator;

/**
 * Style triggers dynamically add or remove style classes from a {@link Node} depending on a user-specified condition.
 *
 * If the condition is true, the specified style classes are added to the {@link Node#getStyleClass()} list;
 * if it is false, the style classes are removed.
 *
 * Once a style trigger is added to {@link Node#getStyleTriggers()}, it is attached to the node and can not
 * be re-used for another node unless it is removed from the original node.
 */
public class StyleTrigger {

    private final BooleanProperty condition = new SimpleBooleanProperty(this, "condition") {
        @Override
        protected void invalidated() {
            boolean value = get();

            if (node == null) {
                return;
            }

            if (value) {
                addStyleClasses(styleClass);
            } else {
                removeStyleClasses(styleClass);
            }
        }
    };

    private final ObservableList styleClass = new TrackableObservableList<>(new ArrayList<>(2)) {
        @Override
        protected void onChanged(ListChangeListener.Change c) {
            if (node == null) {
                return;
            }

            while (c.next()) {
                if (c.getAddedSize() > 0 && isCondition()) {
                    addStyleClasses(c.getAddedSubList());
                }

                if (c.getRemovedSize() > 0) {
                    removeStyleClasses(c.getRemoved());
                }
            }
        }
    };

    private Node node;

    public StyleTrigger() {}

    public StyleTrigger(String... styleClass) {
        this.styleClass.addAll(styleClass);
    }

    /**
     * Gets the list of style classes that will be dynamically added to the {@link Node}'s style class list.
     *
     * @return an {@link ObservableList} of style classes
     */
    public ObservableList getStyleClass() {
        return styleClass;
    }

    /**
     * The condition that determines whether the style classes contained in {@link StyleTrigger#getStyleClass()}
     * are added to the {@link Node}'s style class list.
     */
    public BooleanProperty conditionProperty() {
        return condition;
    }

    public boolean isCondition() {
        return condition.get();
    }

    public void setCondition(boolean value) {
        condition.set(value);
    }

    void setNode(Node node) {
        if (this.node != null && node != null) {
            throw new RuntimeException("Cannot re-use a StyleTrigger that is attached to a Node.");
        }

        if (node == null && this.node != null) {
            removeStyleClasses(styleClass);
        }

        this.node = node;

        if (node != null && isCondition()) {
            addStyleClasses(styleClass);
        }
    }

    private void addStyleClasses(List added) {
        List nodeStyleClass = node.getStyleClass();

        for (String style : added) {
            if (!nodeStyleClass.contains(style)) {
                nodeStyleClass.add(style);
            }
        }
    }

    private void removeStyleClasses(List removed) {
        List nodeStyleClass = node.getStyleClass();

        outer:
        for (String style : removed) {
            ListIterator it = nodeStyleClass.listIterator(nodeStyleClass.size());

            while (it.hasPrevious()) {
                String value = it.previous();

                if (value != null && value.equals(style)) {
                    it.remove();
                    continue outer;
                }
            }
        }
    }

}