Babylon.js/src/Tools/babylon.andOrNotEvaluator.ts

module BABYLON.Internals {
    export class AndOrNotEvaluator {
        public static Eval(query: string, evaluateCallback: (val: any) => boolean): boolean {
            if (!query.match(/\([^\(\)]*\)/g)) {
                query = AndOrNotEvaluator._HandleParenthesisContent(query, evaluateCallback);
            }
            else {
                query = query.replace(/\([^\(\)]*\)/g, r => {
                    // remove parenthesis
                    r = r.slice(1, r.length - 1);
                    return AndOrNotEvaluator._HandleParenthesisContent(r, evaluateCallback);
                });
            }

            if (query === "true") {
                return true;
            }

            if (query === "false") {
                return false;
            }

            return AndOrNotEvaluator.Eval(query, evaluateCallback);
        }

        private static _HandleParenthesisContent(parenthesisContent: string, evaluateCallback: (val) => boolean): string {
            evaluateCallback = evaluateCallback || ((r) => {
                return r === "true" ? true : false;
            });

            var result;
            var or = parenthesisContent.split("||");

            for (var i in or) {
                if (or.hasOwnProperty(i)) {
                    var ori = AndOrNotEvaluator._SimplifyNegation(or[i].trim());
                    var and = ori.split("&&");

                    if (and.length > 1) {
                        for (var j = 0; j < and.length; ++j) {
                            var andj = AndOrNotEvaluator._SimplifyNegation(and[j].trim());
                            if (andj !== "true" && andj !== "false") {
                                if (andj[0] === "!") {
                                    result = !evaluateCallback(andj.substring(1));
                                }
                                else {
                                    result = evaluateCallback(andj);
                                }
                            }
                            else {
                                result = andj === "true" ? true : false;
                            }
                            if (!result) { // no need to continue since 'false && ... && ...' will always return false
                                ori = "false";
                                break;
                            }
                        }
                    }

                    if (result || ori === "true") { // no need to continue since 'true || ... || ...' will always return true
                        result = true;
                        break;
                    }

                    // result equals false (or undefined)

                    if (ori !== "true" && ori !== "false") {
                        if (ori[0] === "!") {
                            result = !evaluateCallback(ori.substring(1));
                        }
                        else {
                            result = evaluateCallback(ori);
                        }
                    }
                    else {
                        result = ori === "true" ? true : false;
                    }
                }
            }

            // the whole parenthesis scope is replaced by 'true' or 'false'
            return result ? "true" : "false";
        }

        private static _SimplifyNegation(booleanString: string): string {
            booleanString = booleanString.replace(/^[\s!]+/, r => {
                // remove whitespaces
                r = r.replace(/[\s]/g, () => "");
                return r.length % 2 ? "!" : "";
            });

            booleanString = booleanString.trim();

            if (booleanString === "!true") {
                booleanString = "false";
            }
            else if (booleanString === "!false") {
                booleanString = "true";
            }

            return booleanString;
        }
    }
}