let register = Toolkit => Toolkit.RadioGroup =

// Radio button group manager
class RadioGroup {

    ///////////////////////// Initialization Methods //////////////////////////

    constructor() {
        this._active = null;
        this.items   = [];
    }



    ///////////////////////////// Public Methods //////////////////////////////

    // The current active radio button
    get active() { return this._active; }
    set active(item) {

        // Error checking
        if (
            item == this.active ||
            item != null && this.items.indexOf(item) == -1
        ) return;

        // De-select the current active item
        if (this.active != null) {
            this.active.checked = false;
            this.active.element.setAttribute("tabindex", "-1");
        }

        // Select the new active item
        this._active = item ? item : null;
        if (item == null)
            return;
        if (!item.checked)
            item.checked = true;
        item.element.setAttribute("tabindex", "0");
    }

    // Add a radio button item
    add(item) {

        // Error checking
        if (
            item == null ||
            this.items.indexOf(item) != -1
        ) return;

        // Remove the item from its current group
        if (item.group != null)
            item.group.remove(item);

        // Add the item to this group
        this.items.push(item);
        item.group = this;
        item.element.setAttribute("tabindex",
            this.items.length == 0 ? "0" : "-1");
        return item;
    }

    // Check whether an element is contained in the radio group
    contains(element) {
        if (element instanceof Toolkit.Component)
            element = element.element;
        return !!this.items.find(i=>i.element.contains(element));
    }

    // Remove a radio button item
    remove(item) {
        let index = this.items.indexOf(item);

        // The item is not in the group
        if (index == -1)
            return null;

        // Remove the item from the group
        this.items.splice(index, 1);
        item.element.setAttribute("tabindex", "0");
        if (this.active == item) {
            this.active = null;
            if (this.items.length != 0)
                this.items[0].element.setAttribute("tabindex", "0");
        }
        return item;
    }



    ///////////////////////////// Package Methods /////////////////////////////

    // Determine the next radio button in the group
    next(item) {
        let index = this.items.indexOf(item);
        return index == -1 ? null :
            this.items[(index + 1) % this.items.length];
    }

    // Determine the previous radio button in the group
    previous(item) {
        let index = this.items.indexOf(item);
        return index == -1 ? null :
            this.items[(index + this.items.length - 1) % this.items.length];
    }

}

export { register };