"use strict";

const defaultValue = require("default-value");
const escapeStringRegexp = require("escape-string-regexp");

const isString = require("@validatem/is-string");
const matchesFormat = require("@validatem/matches-format");
const wrapError = require("@validatem/wrap-error");

function replaceAll(string, search, replace) {
	let regex = new RegExp(escapeStringRegexp(search), "g");

	return string.replace(regex, replace);
}

function generateRequirementsList(requirements) {
	return Object.entries(requirements)
		.filter(([ _key, value ]) => value === true)
		.map(([ key, _value]) => key);
}

module.exports = function makeIsNumericValidator(options = {}) {
	let decimalSeparator = defaultValue(options.decimalSeparator, ".");
	let groupSeparator = defaultValue(options.groupSeparator, ",");
	let allowDecimal = defaultValue(options.allowDecimal, false);
	let allowGroups = defaultValue(options.allowGroups, false);
	let allowNegative = defaultValue(options.allowNegative, false);
	let parse = defaultValue(options.parse, false);

	function parseNumber(value, context) {
		// Automatically avoid parsing if `ignoreResult` has been used
		if (context.parseIntoResult !== false) {
			let strippedValue = (allowGroups)
				? replaceAll(value, groupSeparator, "")
				: value;

			let normalizedValue = (decimalSeparator !== ".")
				? replaceAll(strippedValue, decimalSeparator, ".")
				: strippedValue;

			if (allowDecimal) {
				return parseFloat(normalizedValue);
			} else {
				return parseInt(normalizedValue);
			}
		}
	}

	let integerPartRegex = (allowGroups)
		? `\\d+(${escapeStringRegexp(groupSeparator)}\\d+)*`
		: "\\d+";

	let negativePrefixRegex = (allowNegative)
		? "-?"
		: "";

	let fractionalPartRegex = (allowDecimal)
		? `(${escapeStringRegexp(decimalSeparator)}\\d+)?`
		: "";
	
	let parser = (parse)
		? parseNumber
		: undefined;

	let requirements = generateRequirementsList({
		"whole": !allowDecimal,
		"positive": !allowNegative,
		"ungrouped": !allowGroups
	});

	let requirementsString = (requirements.length > 0)
		? `string representing a ${requirements.join(", ")} number`
		: "numeric string";

	return wrapError(`Must be a ${requirementsString}`, [
		isString,
		matchesFormat(new RegExp(`^${negativePrefixRegex}${integerPartRegex}${fractionalPartRegex}$`)),
		parser
	]);
};