Introduce unzipping and use it

byg/src/DependencyGenerator.hs

@@ -9,8 +9,12 @@ module DependencyGenerator
   , mapDepGenM
   , mapDepGenM_
   , filterDepGenM
+  , unzipFstDepGenM
+  , unzipSndDepGenM
+  , unzipDepGenM
 
   , joinPaths
+  , fileComponents
   , isImageFilename
   , convertedImageFilename
   , applyTemplate
@@ -98,6 +102,27 @@ filterDepGenM f input = do
   conds <- mapDepGenM f input
   genDependency (makeDependency (TupleToken (input, conds)) FilterComp)
 
+unzipFstDepGenM :: TokenableTo [(a, b)] t => t -> DepGenM (Token [a])
+unzipFstDepGenM t = do
+  t' <- toToken t
+  case t' of
+    ZipToken (a, _) -> pure a
+    Token _ -> genDependency (makeDependency t' UnzipFst)
+
+unzipSndDepGenM :: TokenableTo [(a, b)] t => t -> DepGenM (Token [b])
+unzipSndDepGenM t = do
+  t' <- toToken t
+  case t' of
+    ZipToken (_, b) -> pure b
+    Token _ -> genDependency (makeDependency t' UnzipSnd)
+
+unzipDepGenM :: TokenableTo [(a, b)] t => t -> DepGenM (Token [a], Token [b])
+unzipDepGenM t = do
+  t' <- toToken t
+  a <- unzipFstDepGenM t'
+  b <- unzipSndDepGenM t'
+  pure (a, b)
+
 class TokenableTo t s | s -> t where
   toToken :: s -> DepGenM' t
 
@@ -113,6 +138,9 @@ joinPaths (a, b) = do
   b' <- toToken b
   runFunction JoinPaths $ TupleToken (a', b')
 
+fileComponents :: TokenableTo FilePath a => a -> DepGenM' (String, String)
+fileComponents a = runFunction FileComponents =<< toToken a
+
 isImageFilename :: TokenableTo FilePath a => a -> DepGenM' Bool
 isImageFilename a = runFunction IsImageFilename =<< toToken a
 

byg/src/SiteGenerator.hs

@@ -6,6 +6,7 @@ import DependencyGenerator
 handleRecipeDir :: Token FilePath -> Token Template -> Token FilePath -> DepGenM ()
 handleRecipeDir outputDir template dir = do
   dirContents <- listDirectory dir
+  (bases, exts) <- unzipDepGenM (mapDepGenM fileComponents dirContents)
   imageFilenames <- filterDepGenM isImageFilename dirContents
   convertedImageFilenames <- mapDepGenM convertedImageFilename imageFilenames
   mapDepGenM_

byg/src/Types/Dependency.hs

@@ -23,6 +23,8 @@ data Action = Function Function
             | FilterComp
             | GetListElem
             | SetListElem
+            | UnzipFst
+            | UnzipSnd
             | MapComp [Dependency]
   deriving (Show, Lift)
 

byg/src/Types/Function.hs

@@ -5,6 +5,7 @@ module Types.Function
 import Language.Haskell.TH.Syntax (Lift)
 
 data Function = JoinPaths
+              | FileComponents
               | IsImageFilename
               | ConvertedImageFilename
               | ApplyTemplate