"use strict";

const isArguments = require("is-arguments");
const flat = require("array.prototype.flat");

const ValidationError = require("@validatem/error");
const annotateErrors = require("@validatem/annotate-errors");

const applyValidators = require("../apply-validators");
const createValidationMethod = require("./validation-method");

// TODO: Simplify below by treating it like an array or object? Or would that introduce too much complexity through specialcasing?
// TODO: Find a way to produce validatem-style errors for the below invocation errors, without introducing recursion

module.exports = createValidationMethod((args, argumentDefinitions) => {
	if (!isArguments(args)) {
		throw new Error(`First argument is not an 'arguments' object; maybe you forgot to put it before the validation rules?`);
	} else if (argumentDefinitions == null) {
		throw new Error(`Validation rules (second argument) are missing; maybe you forgot to specify them?`);
	} else if (args.length > argumentDefinitions.length) {
		return {
			errors: [ new ValidationError(`Got ${args.length} arguments, but only expected ${argumentDefinitions.length}`) ],
			// Cast the below to an array, for consistency with *success* output, in case we ever want to expose the new values to the user in an error case too.
			newValue: Array.from(args)
		};
	} else {
		let results = argumentDefinitions.map((definition, i) => {
			let argument = args[i];
			let [ argumentName, ...argumentRules ] = definition;

			if (typeof argumentName !== "string") {
				throw new Error("First item in the argument rules list must be the argument name");
			} else {
				let validatorResult = applyValidators(argument, argumentRules);

				return {
					errors: annotateErrors({
						pathSegments: [ argumentName ],
						errors: validatorResult.errors
					}),
					newValue: (validatorResult.newValue !== undefined)
						? validatorResult.newValue
						: argument
				};
			}
		});

		let combinedErrors = results.map((result) => result.errors);
		let flattenedErrors = flat(combinedErrors);

		let newValues = results.map((result) => result.newValue);

		return {
			errors: flattenedErrors,
			newValue: newValues
		};
	}
});