'use strict';

module.exports = class SymbolTreeNode {

constructor() {
        this.parent = null;
        this.previousSibling = null;
        this.nextSibling = null;

        this.firstChild = null;
        this.lastChild = null;

        /** This value is incremented anytime a children is added or removed */
        this.childrenVersion = 0;
        /** The last child object which has a cached index */
        this.childIndexCachedUpTo = null;

        /** This value represents the cached node index, as long as
         * cachedIndexVersion matches with the childrenVersion of the parent */
        this.cachedIndex = -1;
        this.cachedIndexVersion = NaN; // NaN is never equal to anything
}

get isAttached() {
        return Boolean(this.parent || this.previousSibling || this.nextSibling);
}

get hasChildren() {
        return Boolean(this.firstChild);
}

childrenChanged() {
        /* jshint -W016 */
        // integer wrap around
        this.childrenVersion = (this.childrenVersion + 1) & 0xFFFFFFFF;
        this.childIndexCachedUpTo = null;
}

getCachedIndex(parentNode) {
        // (assumes parentNode is actually the parent)
        if (this.cachedIndexVersion !== parentNode.childrenVersion) {
                this.cachedIndexVersion = NaN;
                // cachedIndex is no longer valid
                return -1;
        }

        return this.cachedIndex; // -1 if not cached
}

setCachedIndex(parentNode, index) {
        // (assumes parentNode is actually the parent)
        this.cachedIndexVersion = parentNode.childrenVersion;
        this.cachedIndex = index;
}

};