1 files changed, 200 insertions, 0 deletions
diff --git a/src/TextViewport/Render/Segmentation.hs b/src/TextViewport/Render/Segmentation.hs
new file mode 100644
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+++ b/src/TextViewport/Render/Segmentation.hs
@@ -0,0 +1,200 @@
+module TextViewport.Render.Segmentation where
+
+import Data.DList qualified as DL
+import Data.HashMap.Strict qualified as HM
+import Data.List (minimumBy)
+import Data.Ord (comparing)
+import Data.Text (Text)
+import Data.Text qualified as T
+import Data.Vector (Vector)
+import Data.Vector qualified as V
+import Text.Hyphenation qualified as H
+import TextViewport.Buffer.Item
+import TextViewport.Render.RenderedLine (RenderedLine(..)) -- TODO qualified
+
+applyStrategy :: SegmentStrategy -> Int -> Int -> Text -> Vector RenderedLine
+
+applyStrategy NoSegments width itemIx txt =
+  let rawLines = T.splitOn "\n" txt
+      chunks  = map (T.take width) rawLines -- crop
+      offsets = scanOffsetsWithNewlines chunks
+  in V.fromList
+       [ RenderedLine { rlText = chunk, rlItemIx = itemIx, rlLineIx = lineIx, rlCharStart = off }
+       | (lineIx, (off, chunk)) <- zip [0..] (zip offsets chunks)
+       ]
+
+applyStrategy FixedWidthSegments width itemIx txt =
+  let rawLines = T.splitOn "\n" txt
+      (dl, _) = foldl step (DL.empty, 0) rawLines
+      step (acc, off0) line =
+        let chunks   = chunkFixed width line
+            offsets  = scanOffsetsFrom off0 chunks
+            offNext  = off0 + T.length line + 1
+            acc'     = acc `DL.append` DL.fromList (zip offsets chunks)
+        in (acc', offNext)
+      allChunks = DL.toList dl
+  in V.fromList
+       [ RenderedLine { rlText = chunk, rlItemIx = itemIx, rlLineIx = lineIx, rlCharStart = off }
+       | (lineIx, (off, chunk)) <- zip [0..] allChunks
+       ]
+
+applyStrategy (HyphenateSegments dict cache0) width itemIx txt =
+  let rawLines = T.splitOn "\n" txt
+
+      -- fold over each physical line, accumulating:
+      --   * all rendered (offset, chunk) pairs
+      --   * updated hyphenation cache (unused for now)
+      --   * running character offset across lines
+      (dl, _cache1, _) =
+        foldl segmentOneLine (DL.empty, cache0, 0) rawLines
+      allChunks = DL.toList dl
+  in V.fromList
+       [ RenderedLine { rlText = chunk, rlItemIx = itemIx, rlLineIx = lineIx, rlCharStart = off }
+       | (lineIx, (off, chunk)) <- zip [0..] allChunks
+       ]
+  where
+    -- Segment a single physical line using TeX‑lite hyphenation
+    --segmentOneLine
+    --  :: ([(Int, Text)], HM.HashMap Text [(Text, Text)], Int)
+    --  -> Text
+    --  -> ([(Int, Text)], HM.HashMap Text [(Text, Text)], Int)
+    segmentOneLine (acc, cache, off0) line =
+      let (chunks, cache1) = segmentWithHyphenationTeXLite dict width line cache
+          offsets          = scanOffsetsFrom off0 chunks
+          offNext          = off0 + T.length line + 1
+          acc'             = acc `DL.append` DL.fromList (zip offsets chunks)
+      in (acc', cache1, offNext)
+    --segmentOneLine (acc, cache, off0) line =
+    --  let chunks  = segmentWithHyphenationTeXLite dict width line
+    --      offsets = scanOffsetsFrom off0 chunks
+    --      offNext = off0 + T.length line + 1   -- +1 for newline
+    --      acc'    = acc ++ zip offsets chunks
+    --  in (acc', cache, offNext)
+
+-- | Compute running character offsets for a list of chunks.
+scanOffsetsWithNewlines :: [Text] -> [Int]
+scanOffsetsWithNewlines = go 0
+  where
+    go !_ []     = []
+    go !o (l:ls) =
+      let off = o
+          o'  = o + T.length l + 1   -- +1 for newline
+      in off : go o' ls
+
+-- | Chunk a single line into fixed-width pieces.
+chunkFixed :: Int -> Text -> [Text]
+chunkFixed w t
+  | w <= 0    = []
+  | T.null t  = [""]
+  | otherwise =
+      let (h, rest) = T.splitAt w t
+      in h : if T.null rest then [] else chunkFixed w rest
+
+--------------------------------------------------------------------------------
+-- Hyphenation-aware segmenting (TeX-lite)
+--------------------------------------------------------------------------------
+
+-- Compute offsets starting from a base offset
+scanOffsetsFrom :: Int -> [Text] -> [Int]
+scanOffsetsFrom start = go start
+  where
+    go !_ []     = []
+    go !o (t:ts) = o : go (o + T.length t) ts
+
+segmentWithHyphenationTeXLite
+  :: H.Hyphenator
+  -> Int
+  -> Text
+  -> HM.HashMap Text [(Text, Text)]
+  -> ([Text], HM.HashMap Text [(Text, Text)])
+segmentWithHyphenationTeXLite dict width txt cache0 =
+    go cache0 (T.words txt)
+  where
+    go cache [] = ([], cache)
+    go cache ws =
+      case lineCandidates dict width cache ws of
+        ([], cache1) ->
+          let chunks = breakWordSafe width ws
+          in (chunks, cache1)
+        (cs, cache1) ->
+          let (line, rest, _) =
+                minimumBy (comparing (scoreCandidate width)) cs
+              (more, cache2) = go cache1 rest
+          in (line : more, cache2)
+
+-- | Lossless fallback: treat remaining words as one long text and
+--   chunk it into width-sized pieces. Never truncates, never drops text.
+breakWordSafe :: Int -> [Text] -> [Text]
+breakWordSafe width ws =
+  chunk (T.unwords ws)
+  where
+    chunk t
+      | T.null t            = []
+      | T.length t <= width = [t]
+      | otherwise =
+          let (c, r) = T.splitAt width t
+          in c : chunk r
+
+type Candidate = (Text, [Text], Bool)
+
+lineCandidates
+  :: H.Hyphenator
+  -> Int
+  -> HM.HashMap Text [(Text, Text)]
+  -> [Text]
+  -> ([(Text, [Text], Bool)], HM.HashMap Text [(Text, Text)])
+lineCandidates dict width cache0 ws0 =
+  go [] [] cache0 ws0
+  where
+    go _    acc cache [] = (acc, cache)
+    go line acc cache (w:ws) =
+      let space   = if null line then "" else " "
+          baseTxt = T.unwords line
+          wholeTxt = baseTxt <> space <> w
+          wholeLen = T.length wholeTxt
+
+          acc1 =
+            if wholeLen <= width && not (T.null wholeTxt)
+              then (wholeTxt, ws, False) : acc
+              else acc
+
+          (hyphs, cache1) =
+            case HM.lookup w cache of
+              Just hs -> (hs, cache)
+              Nothing ->
+                let hs = hyphenateWord dict w
+                in (hs, HM.insert w hs cache)
+
+          hyphCands =
+            [ (preTxt, suf : ws, True)
+            | (pre, suf) <- hyphs
+            , not (T.null pre)
+            , let preTxt = baseTxt <> space <> pre <> "-"
+            , T.length preTxt <= width
+            ]
+
+          acc2 = hyphCands ++ acc1
+      in if wholeLen <= width
+           then go (line ++ [w]) acc2 cache1 ws
+           else (acc2, cache1)
+
+hyphenateWord :: H.Hyphenator -> Text -> [(Text, Text)]
+hyphenateWord dict word =
+    let parts = H.hyphenate dict (T.unpack word)
+    in [ ( T.pack (concat (take i parts))
+         , T.pack (concat (drop i parts))
+         )
+       | i <- [1 .. length parts - 1]
+       ]
+
+scoreCandidate :: Int -> Candidate -> Int
+scoreCandidate width (line, _, endsWithHyphen) =
+    let len      = T.length line
+        remSpace = max 0 (width - len)
+        badness  = remSpace * remSpace * remSpace
+        hyphenPenalty =
+          if endsWithHyphen then 50 else 0
+        shortPenalty =
+          if len < width `div` 2 then 200 else 0
+    in badness + hyphenPenalty + shortPenalty
+