"use strict";

const assureArray = require("assure-array");

const combinator = require("@validatem/combinator");
const allowExtraProperties = require("@validatem/allow-extra-properties");

// TODO: Document that this passes on context
// TODO: Clearly document that the predicate is ALSO called when the value is not specified!

module.exports = function (predicate, rules) {
	if (rules == null) {
		// User probably did `[ when(condition), [ rules ] ]` instead of `[ when(condition, [ rules ]) ]`
		throw new Error("No rules specified for a `when` validation clause; did you misplace a parenthese?");
	} else {
		let preparedRules = assureArray(rules).map((rule) => {
			/* We automatically allow extraneous properties in a `when` clause, because it'll generally be used as a partial addition to an otherwise-fully-specified object structure. This can be overridden by using `withContext` explicitly, wrapped directly around the hasShape or object literal. */
			// TODO: Document this.
			return allowExtraProperties(rule);
		});

		return combinator((value, applyValidators, context) => {
			let matches = predicate(value);
	
			if (matches) {
				// TODO: Translate this to a configuration wrapper approach, too?
				return applyValidators(value, preparedRules, context);
			} else {
				// noop
				return;
			}
		});
	}
};