either/index.js

"use strict";

// TODO: Rename this to something more appropriate, like any/anyOf? How to make sure that doesn't cause confusion with `oneOf`?

const ValidationError = require("@validatem/error");
const combinator = require("@validatem/combinator");

module.exports = function (alternatives) {
	if (!Array.isArray(alternatives)) {
		throw new Error(`Must specify an array of alternatives`);
	} else if (alternatives.length < 2) {
		// This doesn't interfere with conditionally-specified alternatives using ternary expressions, because in those cases there is still *some* item specified, it's just going to have a value of `undefined` (and will subsequently be filtered out)
		throw new Error("Must specify at least two alternatives");
	} else if (arguments.length > 1) {
		throw new Error(`Only one argument is accepted; maybe you forgot to wrap the different alternatives into an array?`);
	} else {
		return combinator((value, applyValidators) => {
			let allErrors = [];
	
			for (let alternative of alternatives) {
				let { errors, newValue } = applyValidators(value, alternative);

				if (errors.length === 0) {
					return newValue;
				} else {
					allErrors.push(...errors);
				}
			}

			let errorList = allErrors
				.map((error) => {
					return `"${error.message}"`;
				})
				.join(", ");

			throw new ValidationError(`Must satisfy at least one of: ${errorList}`, { errors: allErrors });
		});
	}
};