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@sjsyrek
Last active September 19, 2019 18:41
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import Data.Semigroup
import Data.Functor
import Control.Applicative
data Validation err a = Failure err | Success a
deriving Show
instance Functor (Validation err) where
fmap f (Success a) = Success (f a)
fmap _ (Failure e) = Failure e
instance Semigroup err => Applicative (Validation err) where
pure = Success
Success f <*> Success a = Success (f a)
Success _ <*> Failure e = Failure e
Failure e <*> Success _ = Failure e
Failure e <*> Failure e' = Failure (e <> e')
instance Foldable (Validation err) where
foldr f x (Success a) = f a x
foldr _ x (Failure _) = x
instance Traversable (Validation err) where
traverse f (Success a) = Success <$> f a
traverse _ (Failure e) = pure (Failure e)
data Form = Form {
email :: String
, password :: String
} deriving Show
data Error =
EmptyField
| NotMinLength
deriving Show
newtype Email = Email String
deriving Show
newtype Password = Password String
deriving Show
data ValidatedForm = ValidatedForm Email Password
deriving Show
type FormValidation = Validation [Error]
notEmpty :: String -> FormValidation String
notEmpty "" = Failure [EmptyField]
notEmpty str = Success str
minLength :: String -> Int -> FormValidation String
minLength str n
| length str >= n = Success str
| otherwise = Failure [NotMinLength]
minPasswordLength :: Int
minPasswordLength = 8
validateEmail :: String -> FormValidation Email
validateEmail input =
notEmpty input $>
Email input
validatePassword :: String -> FormValidation Password
validatePassword input =
notEmpty input *>
minLength input minPasswordLength $>
Password input
validateForm :: Form -> FormValidation ValidatedForm
validateForm (Form email password) =
ValidatedForm <$>
validateEmail email <*>
validatePassword password
mkForm :: String -> String -> FormValidation ValidatedForm
mkForm email password = validateForm $ Form email password
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