1 files changed, 37 insertions, 0 deletions
diff --git a/src/Storage/WatchList.hs b/src/Storage/WatchList.hs
new file mode 100644
index 0000000..11ca3e1
--- /dev/null
+++ b/src/Storage/WatchList.hs
@@ -0,0 +1,37 @@
+module Storage.WatchList (
+    WatchList(..),
+    WatchListItem(..),
+    watchListAdd,
+    watchListDel,
+) where
+
+import Erebos.Object
+import Erebos.Storage.Backend
+import Erebos.Storage.Head
+
+
+data WatchList = WatchList
+    { wlNext :: WatchID
+    , wlList :: [ WatchListItem ]
+    }
+
+data WatchListItem = WatchListItem
+    { wlID :: WatchID
+    , wlHead :: ( HeadTypeID, HeadID )
+    , wlFun :: RefDigest -> IO ()
+    }
+
+watchListAdd :: HeadTypeID -> HeadID -> (RefDigest -> IO ()) -> WatchList -> ( WatchList, WatchID )
+watchListAdd tid hid cb wl = ( wl', wlNext wl )
+  where
+    wl' = wl
+        { wlNext = nextWatchID (wlNext wl)
+        , wlList = WatchListItem
+            { wlID = wlNext wl
+            , wlHead = (tid, hid)
+            , wlFun = cb
+            } : wlList wl
+        }
+
+watchListDel :: WatchID -> WatchList -> WatchList
+watchListDel wid wl = wl { wlList = filter ((/= wid) . wlID) $ wlList wl }