Create project

src/Profold/LineTree.hs

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+module Profold.LineTree
+  ( LineNode(..)
+  , Path
+  , onlyUnfolded
+  , flatten
+  , modify
+  , toggleFold
+  ) where
+
+import qualified Data.Text    as T
+import qualified Data.Vector  as V
+
+import           Profold.Util
+
+data LineNode = LineNode
+  { lineText     :: T.Text
+  , lineChildren :: V.Vector LineNode
+  , lineFolded   :: Bool
+  } deriving (Show)
+
+type Path = [Int]
+
+onlyUnfolded :: LineNode -> LineNode
+onlyUnfolded ln
+  | lineFolded ln = ln{lineChildren = V.empty}
+  | otherwise     = ln
+
+flatten :: LineNode -> V.Vector (Path, T.Text)
+flatten ln =
+  V.cons ([], lineText ln) $
+  V.imap (\i (is, t) -> (i : is, t)) $
+  V.concatMap flatten $
+  lineChildren ln
+
+modify :: (LineNode -> LineNode) -> Path -> LineNode -> LineNode
+modify f [] ln = f ln
+modify f (i:is) ln = ln{lineChildren = modifyAtIndex i (modify f is) $ lineChildren ln}
+
+toggleFold :: Path -> LineNode -> LineNode
+toggleFold = modify $ \ln -> ln{lineFolded = not $ lineFolded ln}

src/Profold/Util.hs

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+module Profold.Util
+  ( modifyAtIndex
+  ) where
+
+import qualified Data.Vector as V
+
+modifyAtIndex :: Int -> (a -> a) -> V.Vector a -> V.Vector a
+-- Yes, this function looks ugly, but it's short enough that I don't care.
+modifyAtIndex i f v = maybe v (\a -> v V.// [(i, f a)]) (v V.!? i)