Kyori Adventure complex localization with arguments (e.g. plural, grammar)

Example.kt

@Suppress("UNUSED")
class MyPlugin : JavaPlugin(), Listener {
	override fun onEnable() {
		super.onEnable()
		server.pluginManager.registerEvents(this, this)
	}

	@EventHandler
	fun onPlayerJoin(event: PlayerJoinEvent) {
		for (i in 1..5) {
			event.player.sendMessage(
				Localization.translatable("welcome", i).args(Component.text(i)).color(NamedTextColor.GREEN)
			)
		}
	}
}

Localization.kt

private data class LocalizationContext(val key: String, val args: Array<out Any>) {
	override fun equals(other: Any?): Boolean {
		if (this === other) return true
		if (javaClass != other?.javaClass) return false

		other as LocalizationContext

		if (key != other.key) return false
		if (!args.contentEquals(other.args)) return false

		return true
	}

	override fun hashCode(): Int {
		var result = key.hashCode()
		result = 31 * result + args.contentHashCode()
		return result
	}
}

object Localization {
	private val localizationCache = mutableMapOf<String, LocalizationContext>()

	fun register() {
		val name = Key.key("network", "translations")
		val registry = TranslationRegistry.create(name)
		registry.register(
			"welcome",
			Locale.ENGLISH,
			MessageFormat("There {0,choice,1#is|1<are} {0,number,integer} {0,choice,1#player|1<players} connected to the network.")
		)
		GlobalTranslator.get().addSource(registry)
		GlobalTranslator.get().addSource(object : Translator {
			override fun name() = name

			override fun translate(key: String, locale: Locale): MessageFormat? {
				val context = localizationCache[key] ?: return null
				val format = GlobalTranslator.get().translate(context.key, locale) ?: return null
				return MessageFormat(format.format(context.args))
			}
		})
	}

	/**
	 * Creates a translatable component with a translation key and arguments.
	 *
	 * @param key the translation key
	 * @param args arguments to use with message format
	 * @return a translatable component
	 */
	fun translatable(key: String, vararg args: Any): TranslatableComponent {
		val context = LocalizationContext(key, args)
		val cacheKey = context.hashCode().toString()
		localizationCache[cacheKey] = context
		return Component.translatable(cacheKey)
	}
}

output.txt

There is 1 player connected to the network.
There are 2 players connected to the network.
There are 3 players connected to the network.
There are 4 players connected to the network.
There are 5 players connected to the network.