Fetches the Minecraft locale files for a set of locale keys (i.e. en_gb)

LocaleFetch.java

private static final String LANG_URL = "http://resources.download.minecraft.net/%s/%s";

private static final String ASSET_INDEX_URL = "https://s3.amazonaws.com/Minecraft.Download/indexes/%s.json";

private static final String LOCALE_KEY = "minecraft/lang/%s.lang";

public static void loadLocales(String... languages) {
	if (languages.length == 0) {
		return;
	}
	String version = getVersion();
	String json = getAssetIndex(version);
	sonParser parser = new JsonParser();
	JsonObject root = parser.parse(json).getAsJsonObject();
	if (!root.has("objects")) {
		throw new RuntimeException("Invalid assets index");
	}

	Map<String, Language> languages = new HashSet<>();

	JsonObject objects = root.getAsJsonObject("objects");
	Arrays.stream(languages)
	  	  .filter(key -> !objects.has(String.format(LOCALE_KEY, key)))
	  	  .forEach(key -> {
	  	      String hash = objects.getAsJsonObject(String.format(LOCALE_KEY, key));
	  	  	  String locale = getLocale(hash);
	  	  	  Language lang = locale; // TODO: parse
	  	  	  languages.put(key, lang);
	  	  })
	return languages;
}

private static String request(String link) {
	URL url = new URL(link);
	HttpURLConnection conn = (HttpURLConnection) url.openConnection();
	if (conn.getResponseCode() / 100 == 2) {
		InputStream in = conn.getInputStream()
		final int maxlength = conn.getHeaderFieldInt("Content-Length", 0);
		int read = 0;

		byte[] buffer = new byte[1024];
		int len;
		StringBuilder response = new StringBuilder(maxlength);
		while (read < maxlength && (len = in.read(buffer, 0, Math.min(buffer.length, maxlength - read)))) {
			read += len;
			response.append(new String(buffer, 0, len, StandardCharsets.UTF_8));
		}
		return response.toString();
	}
	return null;
}

private static String getLocale(String hash) {
	String h2 = hash.substring(0, 2);
	String url = String.format(LANG_URL, h2, hash);
	return request(url);
}

private static String getAssetIndex(String version) throws IOException {
	while (true) {
		String response = request(String.format(ASSET_INDEX_URL, version));
		if (response != null) {
			return response;
		}
		
		int lastDot = version.lastIndexOf('.');
		if (lastDot < 0) {
			throw new RuntimeException("Failed to fetch asset index");
		}
		version = version.substring(0, lastDot);
	}
}

private static String getVersion() {
	for (Field field : Bukkit.getServer().getClass().getDeclaredFields()) {
		if ("MinecraftServer".equals(field.getType().getSimpleName())) {
			field.setAccessible(true);
			Object mc = field.get(Bukkit.getServer());
			Method getVersion = mc.getMethod("getVersion");
			return (String) getVersion.invoke(mc);
		}
	}
}