use errors;
use fmt;
use strings;

// A parsed locale name.
export type locale = struct {
	lang:     str,
	country:  str,
	encoding: str,
	modifier: str,
};

// The default locale. Stands for computer, the C language, etc.
export def c = locale {
	lang = "C",
	...
};

// Parses a [[locale]] name of the form:
// 
//   lang_COUNTRY.ENCODING@MODIFIER
// 
// Where _COUNTRY, .ENCODING, and @MODIFIER may be omitted. The function
// returns a [[locale]], or [[errors::invalid]] if the input cannot be parsed.
// All memory is borrowed from the input, so [[locale_finish]] should not be
// used to free it.
export fn parse_locale(in: str) (locale | errors::invalid) = {
	let (in, modifier) = strings::rcut(in, "@");
	if (strings::compare(in, "") == 0) return void: errors::invalid;
	let (in, encoding) = strings::rcut(in, ".");
	if (strings::compare(in, "") == 0) return void: errors::invalid;
	let (in, country) = strings::rcut(in, "_");
	if (strings::compare(in, "") == 0) return void: errors::invalid;
	return locale {
		lang     = in,
		country  = country,
		encoding = encoding,
		modifier = modifier,
	};
};

// Formats a [[locale]]. The caller must free the return value.
export fn format_locale(local: locale) str = {
	let output = strings::dup(local.lang);
	if (strings::compare(local.country, "") != 0) {
		let new_output = strings::join("_", output, local.country);
		free(output);
		output = new_output;
	};
	if (strings::compare(local.encoding, "") != 0) {
		let new_output = strings::join(".", output, local.encoding);
		free(output);
		output = new_output;
	};
	if (strings::compare(local.modifier, "") != 0) {
		let new_output = strings::join("@", output, local.modifier);
		free(output);
		output = new_output;
	};
	return output;
};

// Checks if two [[locale]]s are equal.
export fn locale_equal(a: locale, b: locale) bool =
	a.lang     == b.lang     &&
	a.country  == b.country  &&
	a.encoding == b.encoding &&
	a.modifier == b.modifier;

// Duplicates a [[locale]] structure. Use [[locale_finish]] to get rid of it.
export fn locale_dup(local: locale) locale = locale {
	lang     = strings::dup(local.lang),
	country  = strings::dup(local.country),
	encoding = strings::dup(local.encoding),
	modifier = strings::dup(local.modifier),
};

// Frees memory associated with a [[locale]] structure.
export fn locale_finish(local: locale) void = {
	free(local.lang);
	free(local.country);
	free(local.encoding);
	free(local.modifier);
};