diff --git a/adiff.cabal b/adiff.cabal
index 4d9120f..38c1de1 100644
--- a/adiff.cabal
+++ b/adiff.cabal
@@ -40,22 +40,31 @@ build-type: Simple
 
 executable adiff
   -- .hs or .lhs file containing the Main module.
-  main-is: MainDiff.hs
+  main-is: Main.hs
 
   -- Modules included in this executable, other than Main.
-  other-modules: Redfa, Version, Diff, Merge
+  other-modules: Diff,
+                 Diff3,
+                 Format,
+                 Merge,
+                 Patch,
+                 Redfa,
+                 Substr,
+                 Types,
+                 Version
 
   -- LANGUAGE extensions used by modules in this package.
   other-extensions: CPP
 
   -- Other library packages from which modules are imported.
   build-depends: base ^>=4.13.0.0,
+                 extra ^>= 1.7,
                  mmap ^>=0.5,
                  regex-tdfa ^>= 1.3,
                  optparse-applicative ^>=0.16,
                  bytestring ^>= 0.10.12,
                  vector ^>=0.12,
-		 utf8-string ^>=1.0
+                 utf8-string ^>=1.0
 
   -- Directories containing source files.
   hs-source-dirs: src
diff --git a/src/Diff.hs b/src/Diff.hs
index e4344c1..dbc2379 100644
--- a/src/Diff.hs
+++ b/src/Diff.hs
@@ -3,10 +3,6 @@ module Diff
   , Op
   , diffToks
   , hunks
-  , pprDiff
-  , pprDiff1
-  , pprHunk
-  , pprHunks
   ) where
 
 import Control.Monad
@@ -16,31 +12,17 @@ import qualified Data.ByteString.Internal as BI
 import qualified Data.ByteString.Lazy as BL
 import Data.ByteString.UTF8 (fromString)
 import Data.Function (on)
-import Data.List (groupBy)
+import Data.List (groupBy, mapAccumL)
+import Data.List.Extra (split, takeEnd)
 import qualified Data.Vector as V
 import qualified Data.Vector.Unboxed.Mutable as M
-
-type Tok = (Bool, (Int, Int))
-
-type Diff = [(Op, Tok)]
-
-type Hunk = ((Int, Int), [(Op, Tok)])
-
-type BS = B.ByteString
-
-type TV = V.Vector Tok
-
-data Op
-  = Remove
-  | Keep
-  | Add
-  deriving (Show, Eq)
+import Debug.Trace
+import Substr
+import Types
 
 data DiffEnv =
   DiffEnv
-    { deD1 :: BS
-    , deD2 :: BS
-    , deT1 :: TV
+    { deT1 :: TV
     , deT2 :: TV
     , deS :: Int
     , deE :: Int
@@ -54,28 +36,21 @@ data DiffEnv =
     }
   deriving (Show)
 
-substr b e = B.take (e - b) . B.drop b
+toksMatch x y DiffEnv {deT1 = t1, deT2 = t2} =
+  t1 V.! x == t2 V.! y
 
-toksMatch x y DiffEnv {deT1 = t1, deT2 = t2, deD1 = d1, deD2 = d2} =
-  toksMatch' x y d1 d2 t1 t2
-
-toksMatch' x y d1 d2 t1 t2 =
-  let (isTok1, (b1, e1)) = t1 V.! x
-      (isTok2, (b2, e2)) = t2 V.! y
-   in isTok1 == isTok2 && substr b1 e1 d1 == substr b2 e2 d2
-
-stripEqToks :: BS -> BS -> TV -> TV -> (Diff, Diff, TV, TV)
-stripEqToks d1 d2 t1 t2 = (pre, post, t1', t2')
+stripEqToks :: TV -> TV -> (Diff, Diff, TV, TV)
+stripEqToks t1 t2 = (pre, post, t1', t2')
   where
     l1 = V.length t1
     l2 = V.length t2
     firstDiff i
-      | i < l1 && i < l2 && toksMatch' i i d1 d2 t1 t2 = firstDiff (i + 1)
+      | i < l1 && i < l2 && (t1 V.! i == t2 V.! i) = firstDiff (i + 1)
       | otherwise = i
     b = firstDiff 0
     lastDiff i
       | l1 - i - 1 >= b &&
-          l2 - i - 1 >= b && toksMatch' (l1 - i - 1) (l2 - i - 1) d1 d2 t1 t2 =
+          l2 - i - 1 >= b && t1 V.! (l1 - i - 1) == t2 V.! (l2 - i - 1)=
         lastDiff (i + 1)
       | otherwise = i
     e = lastDiff 0
@@ -84,19 +59,17 @@ stripEqToks d1 d2 t1 t2 = (pre, post, t1', t2')
     t1' = V.slice b (l1 - e - b) t1
     t2' = V.slice b (l2 - e - b) t2
 
-diffToks :: BS -> BS -> TV -> TV -> Diff
-diffToks d1 d2 t1' t2' = pre ++ res ++ post
+diffToks :: TV -> TV -> Diff
+diffToks t1' t2' = pre ++ res ++ post
   where
-    (pre, post, t1, t2) = stripEqToks d1 d2 t1' t2'
+    (pre, post, t1, t2) = stripEqToks t1' t2'
     res
       | V.null t1 = map (\t -> (Add, t)) (V.toList t2)
       | V.null t2 = map (\t -> (Remove, t)) (V.toList t1)
       | V.length t1 >= V.length t2 =
         diffToks' $
         DiffEnv
-          { deD1 = d1
-          , deD2 = d2
-          , deT1 = t1
+          { deT1 = t1
           , deT2 = t2
           , deS = 0
           , deE = V.length t1
@@ -111,9 +84,7 @@ diffToks d1 d2 t1' t2' = pre ++ res ++ post
       | otherwise =
         diffToks' $
         DiffEnv
-          { deD1 = d2
-          , deD2 = d1
-          , deT1 = t2
+          { deT1 = t2
           , deT2 = t1
           , deS = 0
           , deE = V.length t2
@@ -151,10 +122,10 @@ diffToks' de@DiffEnv {deS = s, deE = e, deA = a, deB = b, deTrans = trans} =
     vecEmid = vecE mid
     extraScore i =
       if isToken
-        then -(tokEnd - tokBegin)
+        then -(B.length s)
         else 0
       where
-        (isToken, (tokBegin, tokEnd)) = deT1 de V.! i
+        (isToken, s) = deT1 de V.! i
     vecS = vec -- "forward" operation
       where
         vec i
@@ -291,70 +262,31 @@ diffToks' de@DiffEnv {deS = s, deE = e, deA = a, deB = b, deTrans = trans} =
         diffToks' de {deE = mid, deVE = vecEmid, deB = opt} ++
         diffToks' de {deS = mid, deVS = vecSmid, deA = opt}
 
-pprDiff :: BS -> BS -> Diff -> [BS]
-pprDiff d1 d2 = map (pprDiff1 d1 d2)
-
-pprDiff1 d1 d2 (op, (tok, (i, j))) =
-  fromString pfx <> escNewlines (substr i j s)
-  where
-    pfx =
-      case (op, tok) of
-        (Add, True) -> "+|"
-        (Remove, True) -> "-|"
-        (Keep, True) -> " |"
-        (Add, False) -> "+."
-        (Remove, False) -> "-."
-        (Keep, False) -> " ."
-    s =
-      case op of
-        Add -> d2
-        _ -> d1
-
-escNewlines = BL.toStrict . BB.toLazyByteString . escNewlines'
-
-escNewlines' s
-  | B.null s = mempty
-  | B.head s == BI.c2w '\n' = BB.stringUtf8 "\\n" <> escNewlines' (B.tail s)
-  | B.head s == BI.c2w '\\' = BB.stringUtf8 "\\\\" <> escNewlines' (B.tail s)
-  | otherwise = BB.word8 (B.head s) <> escNewlines' (B.tail s)
-
 hunks :: Int -> Diff -> [Hunk]
-hunks ctxt = go 0 0 0 0 [] . groupBy ((==) `on` fst)
+hunks ctxt =
+  map (stripNums . concat) .
+  split null .
+  concat . check . map breakKeeps . groupBy ((==) `on` fst . snd) . addNums
   where
-    go _ _ bi bj backlog [] =
-      if null backlog
-        then []
-        else [((bi, bj), backlog)]
-    go i j bi bj backlog (g:gs) =
-      case fst (head g) of
-        Remove -> go (i + length g) j bi bj (backlog ++ g) gs
-        Add -> go i (j + length g) bi bj (backlog ++ g) gs
-        Keep ->
-          let lg = length g
-           in if lg <=
-                 (if null backlog || null g
-                    then ctxt
-                    else 2 * ctxt)
-                then go (i + lg) (j + lg) bi bj (backlog ++ g) gs
-                else (if null backlog
-                        then id
-                        else (:) ((bi, bj), backlog ++ take ctxt g)) $
-                     go
-                       (i + lg)
-                       (j + lg)
-                       (i + lg - ctxt)
-                       (j + lg - ctxt)
-                       (if null gs
-                          then []
-                          else drop (lg - ctxt) g)
-                       gs
-
-hunkHdr i j = fromString $ "@@ -" ++ show i ++ " +" ++ show j ++ " @@"
-
-lineSep = fromString "\n"
-
-pprHunk :: BS -> BS -> Hunk -> BS
-pprHunk d1 d2 ((i, j), toks) =
-  B.intercalate lineSep (hunkHdr i j : pprDiff d1 d2 toks)
-
-pprHunks d1 d2 = B.intercalate lineSep . map (pprHunk d1 d2)
+    addNums = snd . mapAccumL countTok (0, 0)
+    countTok x@(i, j) d@(op, _) =
+      (,)
+        (case op of
+           Remove -> (i + 1, j)
+           Keep -> (i + 1, j + 1)
+           Add -> (i, j + 1))
+        (x, d)
+    stripNums = (,) <$> fst . head <*> map snd
+    breakKeeps ks@((_, (Keep, _)):_) =
+      let (a, b') = splitAt ctxt ks
+          (b, c) = splitAt ctxt b'
+       in if null c
+            then [ks]
+            else [a, [], takeEnd ctxt b']
+    breakKeeps a = [a]
+    check ([_, [], _]:[]) = []
+    check ([_, [], a]:xs) = [a] : checkLast xs
+    check a = checkLast a
+    checkLast [] = []
+    checkLast ([a, [], _]:[]) = [[a]]
+    checkLast (a:xs) = a:checkLast xs
diff --git a/src/Diff3.hs b/src/Diff3.hs
new file mode 100644
index 0000000..b6c2092
--- /dev/null
+++ b/src/Diff3.hs
@@ -0,0 +1,7 @@
+
+module Diff3 where
+
+import Types
+
+diff3Toks :: BS -> BS -> BS -> TV -> TV -> TV -> a
+diff3Toks = undefined
diff --git a/src/Format.hs b/src/Format.hs
new file mode 100644
index 0000000..d4f4308
--- /dev/null
+++ b/src/Format.hs
@@ -0,0 +1,45 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module Format where
+
+import Types
+
+import qualified Data.ByteString as B
+import qualified Data.ByteString.Builder as BB
+import qualified Data.ByteString.Internal as BI
+import qualified Data.ByteString.Lazy as BL
+import Data.String
+import Substr
+
+pprHunkHdr i j = fromString $ "@@ -" ++ show i ++ " +" ++ show j ++ " @@"
+
+lineSep = fromString "\n"
+
+pprHunk :: Hunk -> BS
+pprHunk ((i, j), toks) =
+  B.intercalate lineSep (pprHunkHdr i j : pprDiff toks)
+
+pprHunks = B.intercalate lineSep . map pprHunk
+
+pprDiff :: Diff -> [BS]
+pprDiff = map pprDiff1
+
+pprDiff1 (op, (tok, s)) =
+  fromString pfx <> escNewlines s
+  where
+    pfx =
+      case (op, tok) of
+        (Add, True) -> "+|"
+        (Remove, True) -> "-|"
+        (Keep, True) -> " |"
+        (Add, False) -> "+."
+        (Remove, False) -> "-."
+        (Keep, False) -> " ."
+
+escNewlines = BL.toStrict . BB.toLazyByteString . escNewlines'
+
+escNewlines' s
+  | B.null s = mempty
+  | B.head s == BI.c2w '\n' = BB.stringUtf8 "\\n" <> escNewlines' (B.tail s)
+  | B.head s == BI.c2w '\\' = BB.stringUtf8 "\\\\" <> escNewlines' (B.tail s)
+  | otherwise = BB.word8 (B.head s) <> escNewlines' (B.tail s)
diff --git a/src/MainDiff.hs b/src/Main.hs
similarity index 96%
rename from src/MainDiff.hs
rename to src/Main.hs
index ea60c54..c561a35 100644
--- a/src/MainDiff.hs
+++ b/src/Main.hs
@@ -4,6 +4,7 @@ import qualified Data.ByteString as B
 import qualified Data.ByteString.Char8 as B8
 import Data.ByteString.UTF8 (fromString)
 import qualified Data.Vector as V
+import Format
 import Diff
 import Merge
 import Options.Applicative
@@ -112,6 +113,6 @@ main =
              data2 <- mmapFileByteString f2 Nothing
              toks1 <- V.fromList <$> redfaTokenize redfa data1
              toks2 <- V.fromList <$> redfaTokenize redfa data2
-             let hs = hunks (max 0 ctxt) $ diffToks data1 data2 toks1 toks2
-             B8.putStrLn $ pprHunks data1 data2 hs
+             let hs = hunks (max 0 ctxt) $ diffToks toks1 toks2
+             B8.putStrLn $ pprHunks hs
            CmdPatch {} -> putStrLn "not supported yet"
diff --git a/src/Merge.hs b/src/Merge.hs
new file mode 100644
index 0000000..674d508
--- /dev/null
+++ b/src/Merge.hs
@@ -0,0 +1,67 @@
+module Merge
+  ( MergeOpts
+  , mergeOption
+  ) where
+
+import qualified Data.ByteString as B
+import Data.String
+import Options.Applicative
+import Types
+
+data MergeOpts =
+  MergeOpts
+    { mergeDoMerge :: Bool
+    , mergeForceWhitespace :: Bool
+    , mergeKeepWhitespace :: Bool
+    , mergeCStartStr :: BS
+    , mergeMineSepStr :: BS
+    , mergeYourSepStr :: BS
+    , mergeEndStr :: BS
+    }
+  deriving (Show)
+
+marker = fromString . replicate 7
+
+mergeOption forPatch =
+  MergeOpts <$>
+  switch
+    (short 'm' <>
+     long "merge" <>
+     help
+       (if forPatch
+          then "Merge using conflict markers instead of printing the rejected hunks"
+          else "Output the merged file instead of the patch")) <*>
+  switch
+    (short 'w' <>
+     long "whitespace" <>
+     help
+       ((if forPatch
+           then "Force rejecting a thunk"
+           else "Force a merge conflict") ++
+        " on whitespace mismatch")) <*>
+  switch
+    (short 'k' <>
+     long "keep-whitespace" <>
+     help
+       ("On whitespace mismatch, default to the version from " ++
+        (if forPatch
+           then "original file"
+           else "MYFILE") ++
+        " instead of the one from " ++
+        (if forPatch
+           then "patch"
+           else "YOURFILE"))) <*>
+  strOption
+    (long "merge-start" <>
+     value (marker '<') <> help "Marker for the beginning of a conflict") <*>
+  strOption
+    (long "merge-mine" <>
+     value (marker '|') <>
+     help "Marker that separates `mine' from `original' part of the conflict") <*>
+  strOption
+    (long "merge-your" <>
+     value (marker '=') <>
+     help "Marker that separates `original' from `your' part of the conflict") <*>
+  strOption
+    (long "merge-end" <>
+     value (marker '>') <> help "Marker for the end of a conflict")
diff --git a/src/Patch.hs b/src/Patch.hs
new file mode 100644
index 0000000..08b324f
--- /dev/null
+++ b/src/Patch.hs
@@ -0,0 +1,4 @@
+module Patch where
+
+patchToks :: a
+patchToks = undefined
diff --git a/src/Redfa.hs b/src/Redfa.hs
index 42b1db2..5cccdf0 100644
--- a/src/Redfa.hs
+++ b/src/Redfa.hs
@@ -16,6 +16,7 @@ import qualified Data.Vector as V
 import Options.Applicative
 import Text.Regex.TDFA
 import Diff
+import Substr
 
 type BS = B.ByteString
 
@@ -143,7 +144,7 @@ redfaTokenize' ::
   -> Int
   -> Int
   -> [Int]
-  -> m [(Bool, (Int, Int))]
+  -> m [Tok]
 redfaTokenize' spec s state off visited
   | off >= B.length s = pure []
   | otherwise =
@@ -168,7 +169,7 @@ redfaTokenize' spec s state off visited
           ((rule, (_, len)):_) ->
             let matchLen = len - ooff
              in (if matchLen > 0
-                   then (:) (rrIsToken rule, (off, off + matchLen))
+                   then (:) (rrIsToken rule, substr off matchLen s)
                    else id) <$>
                 redfaTokenize'
                   spec
diff --git a/src/Substr.hs b/src/Substr.hs
new file mode 100644
index 0000000..87b8f1e
--- /dev/null
+++ b/src/Substr.hs
@@ -0,0 +1,7 @@
+module Substr where 
+
+import Types
+import qualified Data.ByteString as B
+
+substr :: Int -> Int -> BS -> BS
+substr b l = B.take l . B.drop b
diff --git a/src/Types.hs b/src/Types.hs
new file mode 100644
index 0000000..d8add21
--- /dev/null
+++ b/src/Types.hs
@@ -0,0 +1,20 @@
+module Types where
+
+import Data.ByteString
+import Data.Vector
+
+type BS = ByteString
+
+type Tok = (Bool, BS)
+
+type TV = Vector Tok
+
+type Diff = [(Op, Tok)]
+
+type Hunk = ((Int, Int), Diff)
+
+data Op
+  = Remove
+  | Keep
+  | Add
+  deriving (Show, Eq)