"luck" as a countable noun?

[Nessie]

1/ Is "luck" ever used as a countable noun? I remember vaguely seeing people use "a bad luck" or "a good luck"

2/ He invited me a glass of fruit juice
=> I think the use of "invited" here is wrong, isn't it?

(By the way, is my tag question above grammatically right?)
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... something we never have again, I know... I guess I really really know..

Sorry seems to be the hardest word...

[Yankee]