Atlatl Kit! Help with projectile spawning

Hello! I am creating a new kit for my server! The name of the kit is Atlatl. Basically it allows the player to rightclick their arrows/spears and when they do, it shoots and arrow out directly in front of them. I want the arrow to give the player it hits a 33% chance of giving the Player slowness. Bad part is.... I have no idea how to do this. I dont know how to spawn an arrow and give it a velocity and how to make it so that it gives the potion effect to the enemy player (the player the arrow hit). Can anyone help me? This is all I have so far.

Code:java

@EventHandler
    public void onAtlatlThrow(PlayerInteractEvent e){
        Player player = e.getPlayer();
        if (e.getAction() == Action.RIGHT_CLICK_AIR && player.getItemInHand().getType() == Material.ARROW){
            if (player.getGameMode() != GameMode.CREATIVE){
                if (player.getItemInHand().getAmount() > 1){
                    player.getItemInHand().setAmount(player.getItemInHand().getAmount() - 1);
                }else{
                    player.setItemInHand(new ItemStack(Material.AIR));    }
            }
        }
    }
}

 

TCO_007
Something like this maybe...

Code:java

Arrow arrow = player.launchProjectile(Arrow.class);
 
arrow.setVelocity(player.getLocation().getDirection());