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module Storage.Merge (
generations,
ancestors,
precedes,
) where
import qualified Data.ByteString.Char8 as BC
import Data.List
import Data.Maybe
import Data.Set (Set)
import qualified Data.Set as S
import Storage
import Storage.Internal
previous :: Storable a => Stored a -> [Stored a]
previous (Stored ref _) = case load ref of
Rec items | Just (RecRef dref) <- lookup (BC.pack "SDATA") items
, Rec ditems <- load dref ->
map wrappedLoad $ catMaybes $ map (\case RecRef r -> Just r; _ -> Nothing) $
map snd $ filter ((== BC.pack "SPREV") . fst) ditems
| otherwise ->
map wrappedLoad $ catMaybes $ map (\case RecRef r -> Just r; _ -> Nothing) $
map snd $ filter ((== BC.pack "PREV") . fst) items
_ -> []
generations :: Storable a => [Stored a] -> [Set (Stored a)]
generations = unfoldr gen . (,S.empty)
where gen (hs, cur) = case filter (`S.notMember` cur) $ previous =<< hs of
[] -> Nothing
added -> let next = foldr S.insert cur added
in Just (next, (added, next))
ancestors :: Storable a => [Stored a] -> Set (Stored a)
ancestors = last . (S.empty:) . generations
precedes :: Storable a => Stored a -> Stored a -> Bool
precedes x y = x `S.member` ancestors [y]
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