import           Prelude hiding (head, init, last, reverse, tail)
import qualified Prelude

import Data.Char                          (isDigit)
import Data.Foldable                      (for_)
import Data.List                          (intercalate, intersperse, isPrefixOf, replicate, stripPrefix)
import Distribution.Simple                (Args, UserHooks (preBuild), defaultMainWithHooks, simpleUserHooks)
import Distribution.Simple.Setup          (BuildFlags)
import Distribution.Types.HookedBuildInfo (HookedBuildInfo, emptyHookedBuildInfo)
import System.Directory                   (copyFile, createDirectoryIfMissing, getTemporaryDirectory, removeFile)
import System.IO                          (Handle, IOMode (ReadMode), hClose, hGetLine, hIsEOF, hPutStrLn,
                                           hSetNewlineMode, noNewlineTranslation, openTempFile, stdin, withFile)

main :: IO ()
main =
  defaultMainWithHooks
    simpleUserHooks
      { preBuild = preProcessListTuple }

preProcessListTuple :: Args -> BuildFlags -> IO HookedBuildInfo
preProcessListTuple _ _ = do
  let
    dir = "src/Data/Tuple"
    file = "List.hs"
    srcPath = dir ++ "/" ++ file
    templatePath = "template/List.hs"
    templateAtPath = "template/ListAt.hs"
  tempPath <-
    withFile srcPath ReadMode $ \src -> do
      tempDir <- (++ "/list-tuple") <$> getTemporaryDirectory
      createDirectoryIfMissing True tempDir
      (tempPath, temp) <- openTempFile tempDir file
      putStrLn $ "temporaly file: " ++ tempPath
      hSetNewlineMode src noNewlineTranslation
      hSetNewlineMode temp noNewlineTranslation
      hSetNewlineMode stdin noNewlineTranslation
      template <- lines <$> readFile templatePath
      templateAt <- lines <$> readFile templateAtPath
      loop src temp template templateAt
      hClose temp
      pure tempPath
  copyFile tempPath srcPath
  removeFile tempPath
  pure emptyHookedBuildInfo
  where
    loop :: Handle -> Handle -> [String] -> [String] -> IO ()
    loop src temp template templateAt =
      go
      where
        go = do
          eof <- hIsEOF src
          if eof
            then pure ()
            else do
              line <- hGetLine src
              for_ (preprocess line template templateAt) (hPutStrLn temp)
              go

    preprocess :: String -> [String] -> [String] -> [String]
    preprocess line template templateAt
      | Just rest <- stripPrefix "---- embed " line
      , let n = read $ takeWhile isDigit rest
      = embed n template templateAt
      | otherwise = [line]

    embed :: Word -> [String] -> [String] -> [String]
    embed l template templateAt
      | l >= 3 = concatMap go template
      | otherwise = error "length must be larger than or equal to 3"
      where
        go "" = [""]
        go t
          | Just rest <- stripPrefix "<tuple>" t = [tuple ++ Prelude.head (go rest)]
          | Just rest <- stripPrefix "<cons>" t = [cons ++ Prelude.head (go rest)]
          | Just rest <- stripPrefix "<tail>" t = [tail ++ Prelude.head (go rest)]
          | Just rest <- stripPrefix "<init>" t = [init ++ Prelude.head (go rest)]
          | Just rest <- stripPrefix "<last>" t = [last ++ Prelude.head (go rest)]
          | Just rest <- stripPrefix "<length>" t = [length ++ Prelude.head (go rest)]
          | Just rest <- stripPrefix "<tuple-head>" t = [tupleHead ++ Prelude.head (go rest)]
          | Just rest <- stripPrefix "<tuple-tail>" t = [tupleTail ++ Prelude.head (go rest)]
          | Just rest <- stripPrefix "<tuple-init>" t = [tupleInit ++ Prelude.head (go rest)]
          | Just rest <- stripPrefix "<tuple-last>" t = [tupleLast ++ Prelude.head (go rest)]
          | Just rest <- stripPrefix "<cons>" t = [cons ++ Prelude.head (go rest)]
          | Just rest <- stripPrefix "<reverse>" t = [reverse ++ Prelude.head (go rest)]
          | Just rest <- stripPrefix "<" t = error $ "unknown tag: " ++ takeWhile (/= '>') rest
          | Just _ <- stripPrefix "---- has-at" t
          = concatMap go $ concat $ intersperse [""] $ embedAt <$> [0 .. l - 1]
          | Just rest <- stripPrefix "-" t = ["-" ++ Prelude.head (go rest)]
          | (s, rest) <- span ((&&) <$> (/= '<') <*> (/= '-')) t = [s ++ Prelude.head (go rest)]
        n = fromIntegral l
        m = n - 1
        tuple = paren $ take n abc
        tail = paren $ take m $ Prelude.tail abc
        init = paren $ take m abc
        last = [last']
        length = show l
        tupleHead = paren $ take n $ 'a' : unders
        tupleTail = paren $ take n $ '_' : Prelude.tail abc
        tupleInit = paren $ Prelude.reverse $ '_' : zy
        tupleLast = paren $ Prelude.reverse $ take n $ last' : unders
        cons = "(" ++ replicate m ',' ++ ")"
        paren xs = "(" ++ intercalate ", " ((: []) <$> xs) ++ ")"
        abc = ['a' ..]
        unders = repeat '_'
        last' = abc !! m
        zy = Prelude.reverse (take m abc)
        zyx = Prelude.reverse (take n abc)
        reverse = paren $ zyx

        embedAt :: Word -> [String]
        embedAt at =
          go <$> templateAt
          where
            go "" = ""
            go t
              | Just rest <- stripPrefix "<at>" t = show at ++ go rest
              | Just rest <- stripPrefix "<item>" t = item ++ go rest
              | Just rest <- stripPrefix "<tuple-at>" t = tupleAt ++ go rest
              | Just rest <- stripPrefix "<" t = "<" ++ go rest
              | (s, rest) <- span (/= '<') t = s ++ go rest
            at' = fromIntegral at
            item = [abc !! at']
            tupleAt = paren $ take at' unders ++ item ++ take (n - at' - 1) unders