1 files changed, 47 insertions, 0 deletions
diff --git a/src/Erebos/Storage/Merge.hs b/src/Erebos/Storage/Merge.hs
new file mode 100644
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+++ b/src/Erebos/Storage/Merge.hs
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+module Erebos.Storage.Merge (
+    Mergeable(..),
+    merge, storeMerge,
+
+    Generation,
+    showGeneration,
+    compareGeneration, generationMax,
+    storedGeneration,
+
+    generations, generationsBy,
+    ancestors,
+    precedes,
+    precedesOrEquals,
+    filterAncestors,
+    storedRoots,
+    walkAncestors,
+
+    findProperty,
+    findPropertyFirst,
+
+    storedDifference,
+) where
+
+import Data.Kind
+
+import Erebos.Object
+import Erebos.Storable.Internal
+import Erebos.Storage.Graph
+
+
+class Storable (Component a) => Mergeable a where
+    type Component a :: Type
+    mergeSorted :: [Stored (Component a)] -> a
+    toComponents :: a -> [Stored (Component a)]
+
+instance Mergeable [Stored Object] where
+    type Component [Stored Object] = Object
+    mergeSorted = id
+    toComponents = id
+
+merge :: Mergeable a => [Stored (Component a)] -> a
+merge [] = error "merge: empty list"
+merge xs = mergeSorted $ filterAncestors xs
+
+storeMerge :: (Mergeable a, Storable a) => [Stored (Component a)] -> IO (Stored a)
+storeMerge [] = error "merge: empty list"
+storeMerge xs@(x : _) = wrappedStore (storedStorage x) $ mergeSorted $ filterAncestors xs