You don't need a stamina bar, just take str / 2 as stamina and reduce the weight of the weapon from that each swing, and use the remaining value to scale animation speed (0 stamina would make you swing half as fast as full). Then readd 2 or 3 to this value up to the limit of str / 2 each second a player is not swinging. Congrats, you have just removed spam from the game!