The PlayerFillBucket Event is fired whenever a player fills a bucket.

You will need to cast the event in the function header as this class:
crafttweaker.event.PlayerFillBucketEvent
You can, of course, also import the class before and use that name then.

PlayerFillBucket Events implement the following interfaces and are able to call all of their methods/getters/setters as well:

• IEventCancelable
• IPlayerEvent
• IProcessableEvent
• IEventPositionable

The following information can be retrieved from the event:

ZenGetter	ZenSetter	Type
ZenGetter ​	ZenSetter result	Type IItemStack
ZenGetter emptyBucket	ZenSetter ​	Type IItemStack
ZenGetter world	ZenSetter ​	Type IWorld
ZenGetter blockState	ZenSetter ​	Type IBlockState
ZenGetter block	ZenSetter ​	Type IBlock
ZenGetter dimension	ZenSetter ​	Type int
ZenGetter rayTraceResult	ZenSetter ​	Type IRayTraceResult

The following information can be retrieved from the event:

ZenGetter	ZenSetter	Type
ZenGetter world	ZenSetter ​	Type IWorld
ZenGetter blockState	ZenSetter ​	Type IBlockState
ZenGetter block	ZenSetter ​	Type IBlock
ZenGetter player	ZenSetter ​	Type IPlayer
ZenGetter result	ZenSetter ​	Type string with value of default, deny or allow
ZenGetter canceled	ZenSetter canceled	Type bool

ZenMethods

• event.deny() Method, sets the event's result to deny
• event.allow() Method, sets the event's result to allow
• event.default() Method, sets the event's result to default
• event.cancel(); Method, returns void (nothing). Can cancel the event and stop something from happening

ZenGetter	ZenSetter	Type
ZenGetter position	ZenSetter ​	Type IBlockPos
ZenGetter x	ZenSetter ​	Type int
ZenGetter y	ZenSetter ​	Type int
ZenGetter z	ZenSetter ​	Type int
ZenGetter entityLivingBase	ZenSetter ​	Type IEntityLivingBase

Because this event extends IProcessableEvent, we have the getter result, but this event also has the setter result. Dont mix them up! You can print(event.result) and will get the string value from above, but if you use event.result = <minecraft:stick> the player will hold a stick in their hand after finishing the event and the bucket "vanishes"