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|
module Resource
( Resource
, createdAt
, editedAt
, deletedAt
, Status(..)
, statuses
, groupByStatus
, statusDuring
) where
import Data.Maybe (fromMaybe)
import Data.Map (Map)
import qualified Data.Map as M
import Data.Time.Clock (UTCTime)
class Resource a where
createdAt :: a -> UTCTime
editedAt :: a -> Maybe UTCTime
deletedAt :: a -> Maybe UTCTime
data Status =
Created
| Edited
| Deleted
deriving (Eq, Show, Read, Ord, Enum, Bounded)
statuses :: [Status]
statuses = [minBound..]
groupByStatus :: Resource a => UTCTime -> UTCTime -> [a] -> Map Status [a]
groupByStatus start end resources =
foldl
(\m resource ->
case statusDuring start end resource of
Just status -> M.insertWith (++) status [resource] m
Nothing -> m
)
M.empty
resources
statusDuring :: Resource a => UTCTime -> UTCTime -> a -> Maybe Status
statusDuring start end resource
| created && not deleted = Just Created
| not created && edited && not deleted = Just Edited
| not created && deleted = Just Deleted
| otherwise = Nothing
where
created = belongs (createdAt resource) start end
edited = fromMaybe False (fmap (\t -> belongs t start end) $ editedAt resource)
deleted = fromMaybe False (fmap (\t -> belongs t start end) $ deletedAt resource)
belongs :: UTCTime -> UTCTime -> UTCTime -> Bool
belongs time start end = time >= start && time < end
|
