From ba1f7d1fb5c8d02a8a07fc05cf7bd5ce722cffb9 Mon Sep 17 00:00:00 2001
From: EncodePanda <paul.szulc@gmail.com>
Date: Fri, 5 Feb 2021 12:51:59 +0100
Subject: [PATCH] Modify Signature to look top level func signatures and
 prepare for formatting

---
 .../Haskell/Stylish/Step/Signature.hs         | 40 ++++++++++++++++++-
 .../Haskell/Stylish/Step/Signature/Tests.hs   |  4 +-
 2 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/lib/Language/Haskell/Stylish/Step/Signature.hs b/lib/Language/Haskell/Stylish/Step/Signature.hs
index 6b1124ce..b4b067a5 100644
--- a/lib/Language/Haskell/Stylish/Step/Signature.hs
+++ b/lib/Language/Haskell/Stylish/Step/Signature.hs
@@ -1,10 +1,46 @@
+{-# LANGUAGE BlockArguments  #-}
+{-# LANGUAGE LambdaCase      #-}
+{-# LANGUAGE TypeApplications #-}
 module Language.Haskell.Stylish.Step.Signature where
 
+import           RdrName                          (RdrName)
+import           SrcLoc                           (GenLocated (..), Located)
+import GHC.Hs.Decls (HsDecl(..))
+import GHC.Hs.Binds (Sig(..))
+import           GHC.Hs.Extension                 (GhcPs)
+
+--------------------------------------------------------------------------------
+import           Language.Haskell.Stylish.Block
 import           Language.Haskell.Stylish.Step
+import           Language.Haskell.Stylish.Module
+import Language.Haskell.Stylish.Editor (change)
+import           Language.Haskell.Stylish.GHC (getStartLineUnsafe, getEndLineUnsafe)
+import           Language.Haskell.Stylish.Editor (Change, applyChanges)
+
+-- TODO unify with type alias from Data.hs
+type ChangeLine = Change String
 
 data Config = Config
-  { maxColumnLength :: Int
+  { cMaxColumns :: Int
   }
 
 step :: Config -> Step
-step _ = makeStep "Signature" (\ls _ -> ls)
+step cfg = makeStep "Signature" (\ls m -> applyChanges (changes cfg m) ls)
+
+changes :: Config -> Module -> [ChangeLine]
+changes cfg m = fmap (formatSignatureDecl cfg m) (topLevelFunctionSignatures m)
+
+topLevelFunctionSignatures :: Module -> [Located SignatureDecl]
+topLevelFunctionSignatures = queryModule @(Located (HsDecl GhcPs)) \case
+  L pos (SigD _ (TypeSig _ [name] _)) -> [L pos $ MkSignatureDecl name]
+  _ -> []
+
+data SignatureDecl = MkSignatureDecl
+  { sigName :: Located RdrName
+  }
+
+formatSignatureDecl :: Config -> Module -> Located SignatureDecl -> ChangeLine
+formatSignatureDecl _cfg _m ldecl = change originalDeclBlock id
+  where
+    originalDeclBlock =
+      Block (getStartLineUnsafe ldecl) (getEndLineUnsafe ldecl)
diff --git a/tests/Language/Haskell/Stylish/Step/Signature/Tests.hs b/tests/Language/Haskell/Stylish/Step/Signature/Tests.hs
index b2a8edbf..267c6ea0 100644
--- a/tests/Language/Haskell/Stylish/Step/Signature/Tests.hs
+++ b/tests/Language/Haskell/Stylish/Step/Signature/Tests.hs
@@ -21,8 +21,8 @@ tests = testGroup "Language.Haskell.Stylish.Step.Signature.Tests"
     ]
 
 config :: Int -> Config
-config maxColumnLength = Config
-  { maxColumnLength = maxColumnLength
+config cMaxColumns = Config
+  { cMaxColumns = cMaxColumns
   }
 
 case00 :: Assertion