/**
 * @param filesize - In bytes.
 * @return Object with quantized filesize and suitable unit of size.
 */
function filesizeToObj(filesize)
{
	// We are unlikely to download files measured in units greater than GiB.
	let units = [
		translateWithContext("filesize unit", "B"),
		translateWithContext("filesize unit", "KiB"),
		translateWithContext("filesize unit", "MiB"),
		translateWithContext("filesize unit", "GiB")
	];

	let i = 0;
	while (i < units.length - 1)
	{
		if (filesize < 1024)
			break;
		filesize /= 1024;
		++i;
	}

	return {
		"filesize": filesize.toFixed(i == 0 ? 0 : 1),
		"unit": units[i]
	};
}

function filesizeToString(filesize)
{
	// Translation: For example: 123.4 KiB
	return sprintf(translate("%(filesize)s %(unit)s"), filesizeToObj(filesize));
}

/**
 * Convert time in milliseconds to [HH:]mm:ss string representation.
 *
 * @param time Time period in milliseconds (integer)
 * @return String representing time period
 */
function timeToString(time)
{
	return Engine.FormatMillisecondsIntoDateStringGMT(time, time < 1000 * 60 * 60 ?
		// Translation: Time-format string. See http://userguide.icu-project.org/formatparse/datetime for a guide to the meaning of the letters.
		translate("mm:ss") : translate("HH:mm:ss"));
}

/**
 * These functions rely on the JS cache where possible and
 * should be prefered over the Engine.Translate ones to optimize the performance.
 */
var g_Translations = {};
var g_PluralTranslations = {};
var g_TranslationsWithContext = {};
var g_PluralTranslationsWithContext = {};

function isTranslatableString(message)
{
	return typeof message == "string" && !!message.trim();
}

/**
 * Translates the specified English message into the current language.
 */
function translate(message)
{
	if (!g_Translations[message])
		g_Translations[message] = Engine.Translate(message);

	return g_Translations[message];
}

/**
 * Translates the specified English message into the current language for the specified number.
 */
function translatePlural(singularMessage, pluralMessage, number)
{
	if (!g_PluralTranslations[singularMessage])
		g_PluralTranslations[singularMessage] = {};

	if (!g_PluralTranslations[singularMessage][number])
		g_PluralTranslations[singularMessage][number] = Engine.TranslatePlural(singularMessage, pluralMessage, number);

	return g_PluralTranslations[singularMessage][number];
}


/**
 * Translates the specified English message into the current language for the specified context.
 */
function translateWithContext(context, message)
{
	if (!g_TranslationsWithContext[context])
		g_TranslationsWithContext[context] = {};

	if (!g_TranslationsWithContext[context][message])
		g_TranslationsWithContext[context][message] = Engine.TranslateWithContext(context, message);

	return g_TranslationsWithContext[context][message];
}


/**
 * Translates the specified English message into the current language for the specified context and number.
 */
function translatePluralWithContext(context, singularMessage, pluralMessage, number)
{
	if (!g_PluralTranslationsWithContext[context])
		g_PluralTranslationsWithContext[context] = {};

	if (!g_PluralTranslationsWithContext[context][singularMessage])
		g_PluralTranslationsWithContext[context][singularMessage] = {};

	if (!g_PluralTranslationsWithContext[context][singularMessage][number])
		g_PluralTranslationsWithContext[context][singularMessage][number] =
			Engine.TranslatePluralWithContext(context, singularMessage, pluralMessage, number);

	return g_PluralTranslationsWithContext[context][singularMessage][number];
}

/**
 * The input object should contain either of the following properties:
 *
 *     • A ‘_string’ property that contains a message to translate.
 *
 *     • A ‘list’ property that contains a list of messages to translate as a
 *     comma-separated list of translated.
 *
 * Optionally, the input object may contain a ‘context’ property. In that case,
 * the value of this property is used as translation context, that is, passed to
 * the translateWithContext(context, message) function.
 */
function translateMessageObject(object)
{
	let trans = translate;
	if (object.context)
		trans = msg => translateWithContext(object.context, msg);

	if (object._string)
		object = trans(object._string);
	else if (object.list)
		object = object.list.map(trans).join(translateWithContext("enumeration", ", "));

	return object;
}

/**
 * Translates any string value in the specified JavaScript object
 * that is associated with a key included in the specified keys array.
 *
 * it accepts an object in the form of
 *
 * {
 *   "translatedString1": "my first message",
 *   "unTranslatedString1": "some English string",
 *   "ignoredObject": {
 *     "translatedString2": "my second message",
 *     "unTranslatedString2": "some English string"
 *   },
 *   "translatedObject1": {
 *     "_string": "my third singular message",
 *     "context": "message context",
 *   },
 *   translatedObject2: {
 *     "list": ["list", "of", "strings"],
 *     "context": "message context",
 *   },
 * }
 *
 * Together with a keys list to translate the strings and objects
 * ["translatedString1", "translatedString2", "translatedObject1",
 * "translatedObject2"]
 *
 * The result will be (f.e. in Dutch)
 * {
 *  "translatedString1": "mijn eerste bericht",
 *   "unTranslatedString1": "some English string",
 *   "ignoredObject": {
 *     "translatedString2": "mijn tweede bericht",
 *     "unTranslatedString2": "some English string"
 *   },
 *   "translatedObject1": "mijn derde bericht",
 *   "translatedObject2": "lijst, van, teksten",
 * }
 *
 * So you see that the keys array can also contain lower-level keys,
 * And that you can include objects in the keys array to translate
 * them with a context, or to join a list of translations.
 *
 * Also, the keys array may be an object where properties are keys to translate
 * and values are translation contexts to use for each key.
 */
function translateObjectKeys(object, keys)
{
	if (keys instanceof Array)
	{
		for (let property in object)
		{
			if (keys.indexOf(property) > -1)
			{
				if (isTranslatableString(object[property]))
					object[property] = translate(object[property]);
				else if (object[property] instanceof Object)
					object[property] = translateMessageObject(object[property]);
			}
			else if (object[property] instanceof Object)
				translateObjectKeys(object[property], keys);
		}
	}
	// If ‘keys’ is not an array, it is an object where keys are properties to
	// translate and values are translation contexts to use for each key.
	// An empty value means no context.
	else
	{
		for (let property in object)
		{
			if (property in keys)
			{
				if (isTranslatableString(object[property]))
					if (keys[property])
						object[property] = translateWithContext(keys[property], object[property]);
					else
						object[property] = translate(object[property]);
				else if (object[property] instanceof Object)
					object[property] = translateMessageObject(object[property]);
			}
			else if (object[property] instanceof Object)
				translateObjectKeys(object[property], keys);
		}
	}
}