-- | Module for the core result type, and related functions
--
module Text.Digestive.Result
( Result (..)
, FormId (..)
, FormRange (..)
, incrementFormId
, isInRange
, isSubRange
, retainErrors
, retainChildErrors
) where
import Control.Applicative (Applicative (..))
-- | Type for failing computations
--
data Result e ok = Error [(FormRange, e)]
| Ok ok
deriving (Show)
instance Functor (Result e) where
fmap _ (Error x) = Error x
fmap f (Ok x) = Ok (f x)
instance Monad (Result e) where
return = Ok
Error x >>= _ = Error x
Ok x >>= f = f x
instance Applicative (Result e) where
pure = Ok
Error x <*> Error y = Error $ x ++ y
Error x <*> Ok _ = Error x
Ok _ <*> Error y = Error y
Ok x <*> Ok y = Ok $ x y
-- | An ID used to identify forms
--
data FormId = FormId
{ formPrefix :: String
, formId :: Integer
} deriving (Eq, Ord)
instance Show FormId where
show (FormId p x) = p ++ "-f" ++ show x
-- | A range of ID's to specify a group of forms
--
data FormRange = FormRange FormId FormId
deriving (Eq, Show)
-- | Increment a form ID
--
incrementFormId :: FormId -> FormId
incrementFormId (FormId p x) = FormId p $ x + 1
-- | Check if a 'FormId' is contained in a 'FormRange'
--
isInRange :: FormId -- ^ Id to check for
-> FormRange -- ^ Range
-> Bool -- ^ If the range contains the id
isInRange (FormId _ a) (FormRange b c) = a >= formId b && a < formId c
-- | Check if a 'FormRange' is contained in another 'FormRange'
--
isSubRange :: FormRange -- ^ Sub-range
-> FormRange -- ^ Larger range
-> Bool -- ^ If the sub-range is contained in the larger range
isSubRange (FormRange a b) (FormRange c d) = formId a >= formId c
&& formId b <= formId d
-- | Select the errors for a certain range
--
retainErrors :: FormRange -> [(FormRange, e)] -> [e]
retainErrors range = map snd . filter ((== range) . fst)
-- | Select the errors originating from this form or from any of the children of
-- this form
--
retainChildErrors :: FormRange -> [(FormRange, e)] -> [e]
retainChildErrors range = map snd . filter ((`isSubRange` range) . fst)