Add a script to split files on lines with a certain pattern

scripts/split.hs

+#!/usr/bin/env -S runhaskell --ghc-arg="-Wall" --ghc-arg="-i lib/haskell"
+
+import Control.Applicative ((<**>), (<|>))
+import Data.List (foldl')
+import Data.Text (Text)
+import Data.Text.IO as Text (getContents, writeFile)
+import Options.Applicative
+  ( Parser, execParser, flag', fullDesc, help, helper, info, long, metavar
+  , progDesc, short, strArgument, strOption)
+import System.Directory (createDirectoryIfMissing)
+import System.FilePath (takeDirectory)
+import Text.Filter (Editable(..))
+import Text.Printf (printf)
+import Text.Regex.TDFA ((=~))
+
+data Mode = Discard | StartWith | EndWith
+
+data Config = Config
+  { splitPattern :: String
+  , mode :: Mode
+  , outputPattern :: String }
+
+configParser :: Parser Config
+configParser = Config
+  <$> strOption on
+  <*> (flag' StartWith startWith <|> flag' EndWith endWith <|> pure Discard)
+  <*> strArgument outputPattern
+  where
+    on = short 'o' <> long "on" <> metavar "REGEX"
+      <> help "pattern of the lines on which to split"
+    outputPattern =
+      metavar "OUTPUT_PATTERN" <> help "pattern of the output files"
+    startWith =
+      short 's' <> long "start" <> help "a part begins with the pattern"
+    endWith = short 'e' <> long "end" <> help "a part ends with the pattern"
+
+getConfig :: IO Config
+getConfig = execParser
+  (info
+    (configParser <**> helper)
+    (fullDesc
+    <> progDesc "A tool to split a textual flow on a predefined line or prefix"))
+    
+split :: Config -> [Text] -> [[Text]]
+split (Config {splitPattern, mode}) = reverse . close . foldl' aggregate ([], [])
+  where
+    close (currentPart, previousParts) = reverse currentPart:previousParts
+    aggregate tmp@(currentPart, previousParts) line
+      | line =~ splitPattern =
+        case mode of
+          Discard -> ([], close tmp)
+          StartWith -> ([line], close tmp)
+          EndWith -> ([], close (line:currentPart, previousParts))
+      | otherwise = (line:currentPart, previousParts)
+
+create :: Editable a => Config -> [a] -> IO ()
+create (Config {outputPattern}) = mapM_ createFile . zip [1..] . fmap leave
+  where
+    createFile :: (Int, Text) -> IO ()
+    createFile (i, content) =
+      let path = printf outputPattern i in do
+      createDirectoryIfMissing True (takeDirectory path)
+      Text.writeFile path content
+
+main :: IO ()
+main = do
+  config <- getConfig
+  Text.getContents >>= create config . split config . enter