/**
 * Usage:
 * import i18n from './i18n.js'
 *
 * console.log( i18n('parentcontext.childcontext.key', {user: username}) );
 *
 * language is loaded from cookie: lang=XX
 * translations are loaded from /public/i18n/XX.txt
 *
 */

const default_lang = "EN";
let langs;


/**
 * Fetch the translation from a key using the current language.
 * could also replace certain value of the form `$variable` by providing an object
 * with { variable: "value" }
 * @param key :string translation key (can be null)
 * @param options: Object element to replace in the translation
 *
 * @return :string The translated text
 */
function i18n(key, options) {
	let ret = langs[key];
	if(options != null){
		for (let key in options) {
			ret = ret.replaceAll("$" + key, options[key]);
		}
	}
	return ret;
}

async function reloadLang(){
	langs = await loadLangs();
}
reloadLang();

export default i18n;


//
// Those functions are utility functions use by previous exported functions.
//

/**
 * Return the content of a cookie with specified key
 * @param key cookie name
 */
function getCookie(key){
	key = key + "="
	let cookies = decodeURIComponent(document.cookie).split(";");
	for (let el of cookies) {
		el = el.trimStart();
		if(el.indexOf(key) == 0){
			return el.substr(key.length, el.length);
		}
	}
	return "";
}

/**
 * Function that load the file with translation from the specified lang and return a dictionnary
 * @param select the language to load. could be null to fetch the cookies for an answer
 * if nothing is found. default to EN.txt
 */
async function loadLangs(lang){
	lang = lang != null ? lang : getCookie("lang");
	lang = lang != "" ? lang : default_lang;

	const filename = "./i18n/" + lang.toUpperCase() + ".txt";
	const content = await (await fetch(filename)).text();
	const lines = content.split("\n");

	let filteredLines = {};
	for (let line of lines) {
		if(!line.trim().startsWith("#") && line.trim() != ""){
			let split = line.indexOf("=")
			filteredLines[line.substr(0, split)] = line.substr(split+1, line.length);
		};
	}
	return filteredLines;
}