Maybe.Extra

{-| Takes two maybe values and maybe test. Returns first maybe value if test is just true.
Otherwise returns second maybe value if test is just false.
-}
maybeAndWhenOrHelper : Maybe a -> Maybe a -> Maybe Bool -> Maybe a
maybeAndWhenOrHelper maybeValueWhen maybeValueWhenNot =
    let
        doTest test =
            if test then
                maybeValueWhen
            else
                maybeValueWhenNot
    in
    Maybe.andThen doTest


{-| Takes two values and maybe test. Returns just first value if test is just true.
Otherwise returns just second value if test is just false.

    maybeAndWhenOr 42 24 (Just True)  == Just 42
    maybeAndWhenOr 42 24 (Just False) == Just 24
    maybeAndWhenOr 42 24 Nothing      == Nothing
-}
maybeAndWhenOr : a -> a -> Maybe Bool -> Maybe a
maybeAndWhenOr valueWhen valueWhenNot =
    maybeAndWhenOrHelper (Just valueWhen) (Just valueWhenNot)


{-| Takes some value and maybe test. Returns just value if test is just true.
Otherwise returns nothing.

    maybeAndWhen 42 (Just True)  == Just 42
    maybeAndWhen 42 (Just False) == Nothing
    maybeAndWhen 42 Nothing      == Nothing
-}
maybeAndWhen : a -> Maybe Bool -> Maybe a
maybeAndWhen value =
    maybeAndWhenOrHelper (Just value) Nothing


{-| Takes some value and maybe test. Returns just value if test is just false.
Otherwise returns nothing.

    maybeAndWhenNot 42 (Just True)  == Nothing
    maybeAndWhenNot 42 (Just False) == Just 42
    maybeAndWhenNot 42 Nothing      == Nothing
-}
maybeAndWhenNot : a -> Maybe Bool -> Maybe a
maybeAndWhenNot value =
    maybeAndWhenOrHelper Nothing (Just value)