Validation system for cerebral actions using tcomb

action-validator.js

function checkValue (msg, value, type) {
	const check = t.validate(value, type);
	if (!check.isValid()) {
		console.error(msg + ' ' + check.firstError().message);
	}
	return value;
}

// This method accepts an object and returns a function that 
// wraps the actual action functions
t.action = function t$action ({ fn, inputs, outputs, resolves, rejects }) {
	if (__DEV__) {
		/* eslint no-new-func: 0 */

		const namedFunction = (name, func) => new Function('fn',
			`return function ${name} (){ return fn.apply(this,arguments)}`
		)(func);

		const Inputs = t.struct(inputs);

		// Async actions
		if (fn.length > 2 || resolves || rejects) {
			const Resolved = !resolves ? t.Nil : t.struct(resolves);
			const Rejected = !rejects ? t.Nil : t.struct(rejects);

			return namedFunction(fn.name, (args, state, promise) => {
				checkValue(`[${fn.name}:inputs]`, args, Inputs);

				fn(args, state, {
					resolve (obj) {
						checkValue(`[${fn.name}:resolves]`, obj, Resolved);
						promise.resolve(obj);
					},
					reject (obj) {
						checkValue(`[${fn.name}:rejects]`, obj, Rejected);
						promise.reject(obj);
					}
				});
			});

		}

		// Sync actions
		const Returned = !outputs ? t.Nil : t.struct(outputs);
		return namedFunction(fn.name, (args, state) => {
			checkValue(`[${fn.name}:inputs]`, args, Inputs);
			const result = fn(args, state);
			checkValue(`[${fn.name}:outputs]`, result, Returned);
			return result;
		});
	}

	return fn;
};