class Core : JavaPlugin() {

    override fun onEnable() {
        getCommand("fly").executor = FlyCommand
        server.pluginManager.registerEvents(EntityEvent, this)
    }
}


object FlyCommand : CommandExecutor {

    fun checkFlight(player: Player, b: Boolean, sender: Player) {
        if (player.isFlying) {
            player.isFlying = false
            player.sendMessage("You are no longer flying.")
            if (b) {
                sender.sendMessage(player.name + " is no longer flying.")
            }
        } else {
            player.isFlying = true
            player.sendMessage("You are now flying.")
            if (b) {
                sender.sendMessage(player.name + " is now flying.")
            }
        }
    }

    override fun onCommand(sender: CommandSender?, cmd: Command?, label: String?, args: Array<out String>?): Boolean {
        if (args!!.size < 2) {
            if (args.isEmpty()) {
                val player = sender as Player
                checkFlight(player, false, player)
                return true
            }

            try {
                val target = Bukkit.getPlayer(args[0])
                checkFlight(target, true, sender as Player);
            } catch (e: Exception) {
                sender?.sendMessage("&cPlayer can't be found.")
            }

        } else {
            sender?.sendMessage("&cUsage: /fly Optional : <player>")
        }
        return false
    }
}