node-data-modeling/src/guard-function.js

"use strict";

const generateValidator = require("./generate-validator");

module.exports = function guardFunction(args, returnType, func) {
	let rules = args.map((arg) => {
		return generateValidator(arg);
	});

	let returnValueValidator = generateValidator(returnType);

	let guardedFunction = function (...params) {
		let paramsWithDefaults = new Array(params.length);

		/* TODO: Can this be made faster by manually incrementing the index outside of the loop, or even by using forEach? ref https://jsperf.com/for-of-vs-foreach-with-index */
		for (let [i, rule] of rules.entries()) {
			let validatorResult = rule.call(this, params[i]);

			if (validatorResult === true) {
				paramsWithDefaults[i] = params[i];
			} else if (validatorResult._default !== undefined) {
				paramsWithDefaults[i] = validatorResult._default;
			} else {
				throw validatorResult;
			}
		}

		let returnValue = func.apply(this, paramsWithDefaults);
		let returnValueValidatorResult = returnValueValidator.call(this, returnValue);

		if (returnValueValidatorResult === true) {
			return returnValue;
		} else if (returnValueValidatorResult._default !== undefined) {
			return returnValueValidatorResult.default;
		} else {
			throw returnValueValidatorResult;
		}
	};

	guardedFunction._guardedArgs = args;
	guardedFunction._guardedReturnType = returnType;
	guardedFunction._guardedFunction = func;

	return guardedFunction;
};