// A string localized into multiple locales.
export type string = [](locale, str);

// -------------------------------------------------------------------------- //
// The matching is done as follows. If LC_MESSAGES is of the form
// lang_COUNTRY.ENCODING@MODIFIER, then it will match a key of the form
// lang_COUNTRY@MODIFIER. If such a key does not exist, it will attempt to match
// lang_COUNTRY followed by lang@MODIFIER. Then, a match against lang by itself
// will be attempted. Finally, if no matching key is found the required key
// without a locale specified is used. The encoding from the LC_MESSAGES value
// is ignored when matching.
// 
// If LC_MESSAGES does not have a MODIFIER field, then no key with a modifier
// will be matched. Similarly, if LC_MESSAGES does not have a COUNTRY field,
// then no key with a country specified will be matched. If LC_MESSAGES just has
// a lang field, then it will do a straight match to a key with a similar value.
// -------------------------------------------------------------------------- //

// Selects the most appropriate localized version of a [[string]] given a
// [[locale]]. The matching algorithm used is the one specified by the
// XDG Desktop Entry Specification, §5, with the addition of a preliminary step
// where a match against the exact locale is attempted. If no suitable version
// is found, an exact match with the C locale will be attempted. If there are
// none, void will be returned. Memory is borrowed from the input.
export fn string_resolve(strin: string, local: locale) (str | void) = {
	// lang_COUNTRY@MODIFIER.ENCODING
	match (string_resolve_exact(strin, local)) {
	case let result: str => return result;
	case                 => void;
	};
	
	// lang_COUNTRY@MODIFIER
	let lang_country_modifier = local;
	lang_country_modifier.encoding = "";
	match (string_resolve_exact(strin, lang_country_modifier)) {
	case let result: str => return result;
	case                 => void;
	};
	
	// lang_COUNTRY
	let lang_country = local;
	lang_country.modifier = "";
	match (string_resolve_exact(strin, lang_country)) {
	case let result: str => return result;
	case                 => void;
	};
	
	// lang@MODIFIER
	let lang_modifier = lang_country_modifier;
	lang_modifier.country = "";
	match (string_resolve_exact(strin, lang_modifier)) {
	case let result: str => return result;
	case                 => void;
	};

	// lang
	let lang = lang_modifier;
	lang.modifier = "";
	match (string_resolve_exact(strin, lang)) {
	case let result: str => return result;
	case                 => void;
	};

	// fallback to c locale
	match (string_resolve_exact(strin, c)) {
	case let result: str => return result;
	case                 => void;
	};
	
	return void;
};

fn string_resolve_exact(strin: string, local: locale) (str | void) = {
	for (let pair .. strin) if(equal(pair.0, local)) return pair.1;
};

// A list of strings localized into multiple locales.
export type strings = [](locale, []str);

// Selects the most appropriate localized version of a [[string]] given a
// [[locale]]. See the documentation for [[string_resolve]] for more
// information.
export fn strings_resolve(strins: strings, local: locale) ([]str | void) = {
	// lang_COUNTRY@MODIFIER.ENCODING
	match (strings_resolve_exact(strins, local)) {
	case let result: []str => return result;
	case                   => void;
	};
	
	// lang_COUNTRY@MODIFIER
	let lang_country_modifier = local;
	lang_country_modifier.encoding = "";
	match (strings_resolve_exact(strins, lang_country_modifier)) {
	case let result: []str => return result;
	case                   => void;
	};
	
	// lang_COUNTRY
	let lang_country = local;
	lang_country.modifier = "";
	match (strings_resolve_exact(strins, lang_country)) {
	case let result: []str => return result;
	case                   => void;
	};
	
	// lang@MODIFIER
	let lang_modifier = lang_country_modifier;
	lang_modifier.country = "";
	match (strings_resolve_exact(strins, lang_modifier)) {
	case let result: []str => return result;
	case                   => void;
	};

	// lang
	let lang = lang_modifier;
	lang.modifier = "";
	match (strings_resolve_exact(strins, lang)) {
	case let result: []str => return result;
	case                   => void;
	};

	// fallback to c locale
	match (strings_resolve_exact(strins, c)) {
	case let result: []str => return result;
	case                   => void;
	};
	
	return void;
};

fn strings_resolve_exact(strins: strings, local: locale) ([]str | void) = {
	for (let pair .. strins) if(equal(pair.0, local)) return pair.1;
};