/**
* https://unicode.org/reports/tr35/tr35-dates.html#Date_Field_Symbol_Table
* Credit: https://github.com/caridy/intl-datetimeformat-pattern/blob/master/index.js
* with some tweaks
*/
const DATE_TIME_REGEX = /(?:[Eec]{1,6}|G{1,5}|[Qq]{1,5}|(?:[yYur]+|U{1,5})|[ML]{1,5}|d{1,2}|D{1,3}|F{1}|[abB]{1,5}|[hkHK]{1,2}|w{1,2}|W{1}|m{1,2}|s{1,2}|[zZOvVxX]{1,4})(?=([^']*'[^']*')*[^']*$)/g;
/**
* Parse Date time skeleton into Intl.DateTimeFormatOptions
* Ref: https://unicode.org/reports/tr35/tr35-dates.html#Date_Field_Symbol_Table
* @public
* @param skeleton skeleton string
*/
export function parseDateTimeSkeleton(skeleton) {
	const result = {};
	skeleton.replace(DATE_TIME_REGEX, (match) => {
		const len = match.length;
		switch (match[0]) {
			case "G":
				result.era = len === 4 ? "long" : len === 5 ? "narrow" : "short";
				break;
			case "y":
				result.year = len === 2 ? "2-digit" : "numeric";
				break;
			case "Y":
			case "u":
			case "U":
			case "r": throw new RangeError("`Y/u/U/r` (year) patterns are not supported, use `y` instead");
			case "q":
			case "Q": throw new RangeError("`q/Q` (quarter) patterns are not supported");
			case "M":
			case "L":
				result.month = [
					"numeric",
					"2-digit",
					"short",
					"long",
					"narrow"
				][len - 1];
				break;
			case "w":
			case "W": throw new RangeError("`w/W` (week) patterns are not supported");
			case "d":
				result.day = ["numeric", "2-digit"][len - 1];
				break;
			case "D":
			case "F":
			case "g": throw new RangeError("`D/F/g` (day) patterns are not supported, use `d` instead");
			case "E":
				result.weekday = len === 4 ? "long" : len === 5 ? "narrow" : "short";
				break;
			case "e":
				if (len < 4) {
					throw new RangeError("`e..eee` (weekday) patterns are not supported");
				}
				result.weekday = [
					"short",
					"long",
					"narrow",
					"short"
				][len - 4];
				break;
			case "c":
				if (len < 4) {
					throw new RangeError("`c..ccc` (weekday) patterns are not supported");
				}
				result.weekday = [
					"short",
					"long",
					"narrow",
					"short"
				][len - 4];
				break;
			case "a":
				result.hour12 = true;
				break;
			case "b":
			case "B": throw new RangeError("`b/B` (period) patterns are not supported, use `a` instead");
			case "h":
				result.hourCycle = "h12";
				result.hour = ["numeric", "2-digit"][len - 1];
				break;
			case "H":
				result.hourCycle = "h23";
				result.hour = ["numeric", "2-digit"][len - 1];
				break;
			case "K":
				result.hourCycle = "h11";
				result.hour = ["numeric", "2-digit"][len - 1];
				break;
			case "k":
				result.hourCycle = "h24";
				result.hour = ["numeric", "2-digit"][len - 1];
				break;
			case "j":
			case "J":
			case "C": throw new RangeError("`j/J/C` (hour) patterns are not supported, use `h/H/K/k` instead");
			case "m":
				result.minute = ["numeric", "2-digit"][len - 1];
				break;
			case "s":
				result.second = ["numeric", "2-digit"][len - 1];
				break;
			case "S":
			case "A": throw new RangeError("`S/A` (second) patterns are not supported, use `s` instead");
			case "z":
				result.timeZoneName = len < 4 ? "short" : "long";
				break;
			case "Z":
			case "O":
			case "v":
			case "V":
			case "X":
			case "x": throw new RangeError("`Z/O/v/V/X/x` (timeZone) patterns are not supported, use `z` instead");
		}
		return "";
	});
	return result;
}