Validation.elm

type alias Fields =
    { data1 : Maybe String 
    , data2 : Maybe Int
    , data3 : Maybe Bool
    }


type alias Submission =
    { data1 : String
    , data2 : Int
    , data3 : Bool
    }


type Error 
    = Error


validate : Fields -> Result Error Submission
validate fields =
    Submission
        |> Ok
        |> give fields.data1
        |> give fields.data2
        |> give fields.data3


give : Maybe a -> Result Error (a -> b) -> Result Error b
give maybeValue result =
    case maybeValue of
        Just value ->
            case result of
                Ok ctor ->
                    Ok (ctor value)

                Err err ->
                    Err err

        Nothing ->
            Err Error