{-# LANGUAGE GADTs #-}
module Game.Chess.PGN (
  readPGNFile, gameFromForest, PGN(..), Game, Outcome(..)
, hPutPGN, pgnDoc, RAVOrder, breadthFirst, depthFirst, gameDoc) where

import Control.Monad
import Data.Bifunctor
import Data.ByteString.Char8 (ByteString)
import qualified Data.ByteString.Char8 as BS
import Data.Char
import Data.Foldable
import Data.Functor
import Data.Maybe
import Data.Text (Text)
import qualified Data.Text as T
import qualified Data.Text.Encoding as T
import Data.Text.Prettyprint.Doc hiding (space)
import Data.Text.Prettyprint.Doc.Render.Text
import Data.Tree
import Data.Word
import Data.Void
import Game.Chess
import System.IO
import Text.Megaparsec
import Text.Megaparsec.Byte
import qualified Text.Megaparsec.Byte.Lexer as L

gameFromForest :: [(ByteString, Text)] -> Forest Ply -> Outcome -> Game
gameFromForest tags forest o = (("Result", r):tags, (o, (fmap . fmap) f forest)) where
  f pl = PlyData [] pl []
  r = case o of
    Win White -> "1-0"
    Win Black -> "0-1"
    Draw      -> "1/2-1/2"
    Undecided -> "*"

newtype PGN = PGN [Game] deriving (Eq, Monoid, Semigroup)
type Game = ([(ByteString, Text)], (Outcome, Forest PlyData))
data Outcome = Win Color
             | Draw
             | Undecided
             deriving (Eq, Show)

instance Pretty Outcome where
  pretty (Win White) = "1-0"
  pretty (Win Black) = "0-1"
  pretty Draw        = "1/2-1/2"
  pretty Undecided   = "*"

data PlyData = PlyData {
  prefixNAG :: ![Int]
, ply :: !Ply
, suffixNAG :: ![Int]
} deriving (Eq, Show)

readPGNFile :: FilePath -> IO (Either String PGN)
readPGNFile fp = first errorBundlePretty . parse pgn fp <$> BS.readFile fp

hPutPGN :: Handle -> RAVOrder (Doc ann) -> PGN -> IO ()
hPutPGN h ro (PGN games) = for_ games $ \game -> do
  hPutDoc h $ gameDoc ro game
  hPutStrLn h ""

type Parser = Parsec Void ByteString

spaceConsumer :: Parser ()
spaceConsumer = L.space
  space1 (L.skipLineComment ";") (L.skipBlockComment "{" "}")

lexeme :: Parser a -> Parser a
lexeme = L.lexeme spaceConsumer

eog :: Parser Outcome
eog = lexeme $  string "1-0" $> Win White
            <|> string "0-1" $> Win Black
            <|> string "1/2-1/2" $> Draw
            <|> string "*" $> Undecided

sym :: Parser ByteString
sym = lexeme . fmap fst . match $ do
  void $ alphaNumChar
  many $ alphaNumChar <|> oneOf [35,43,45,58,61,95]

lbraceChar, rbraceChar, semiChar, periodChar, quoteChar, backslashChar, dollarChar :: Word8
lbraceChar    = fromIntegral $ ord '{'
rbraceChar    = fromIntegral $ ord '}'
semiChar      = fromIntegral $ ord ';'
periodChar    = fromIntegral $ ord '.'
quoteChar     = fromIntegral $ ord '"'
backslashChar = fromIntegral $ ord '\\'
dollarChar    = fromIntegral $ ord '$'

lbracketP, rbracketP, lparenP, rparenP :: Parser ()
lbracketP = void . lexeme . single . fromIntegral $ ord '['
rbracketP = void . lexeme . single . fromIntegral $ ord ']'
lparenP   = void . lexeme . single . fromIntegral $ ord '('
rparenP   = void . lexeme . single . fromIntegral $ ord ')'

nag :: Parser Int
nag = lexeme $  single dollarChar *> L.decimal
            <|> string "!!" $> 3
            <|> string "??" $> 4
            <|> string "!?" $> 5
            <|> string "?!" $> 6
            <|> string "!"  $> 1
            <|> string "?"  $> 2

comment :: Parser String
comment = (fmap . fmap) (chr . fromEnum) $
      single semiChar *> manyTill anySingle (eof <|> void eol)
  <|> single lbraceChar *> many (anySingleBut rbraceChar) <* single rbraceChar

tagPair :: Parser (ByteString, Text)
tagPair = lexeme $ do
  lbracketP
  k <- sym
  v <- str
  rbracketP
  pure $ (k, v)

tagList :: Parser [(ByteString, Text)]
tagList = many tagPair

movetext :: Position -> Parser (Outcome, Forest PlyData)
movetext pos = (,[]) <$> eog <|> main pos where
  main p = ply p >>= \(m, n) -> fmap n <$> movetext (unsafeDoPly p m)
  var p = ply p >>= \(m, n) -> n <$> (rparenP $> [] <|> var (unsafeDoPly p m))
  ply p = do
    pnags <- many nag
    validateMoveNumber p
    m <- lexeme $ relaxedSAN p
    snags <- many nag
    rav <- concat <$> many (lparenP *> var p)
    pure $ (m, \xs -> Node (PlyData pnags m snags) xs:rav)
  validateMoveNumber p =
    optional (lexeme $ L.decimal <* space <* many (single periodChar)) >>= \case
      Just n | moveNumber p /= n ->
        fail $ "Invalid move number: " <> show n <> " /= " <> show (moveNumber p)
      _ -> pure ()

pgn :: Parser PGN
pgn = spaceConsumer *> fmap PGN (many game) <* spaceConsumer <* eof

game :: Parser Game
game = do
  tl <- tagList
  pos <- case lookup "FEN" tl of
    Nothing -> pure startpos
    Just fen -> case fromFEN (T.unpack fen) of
      Just p -> pure p
      Nothing -> fail "Invalid FEN"
  (tl,) <$> movetext pos
  
str :: Parser Text
str = p <?> "string" where
  p = fmap (T.pack . fmap (chr . fromEnum)) $ single quoteChar *> many ch <* single quoteChar
  ch = single backslashChar *> (  single backslashChar $> backslashChar
                          <|> single quoteChar $> quoteChar
                           )
   <|> anySingleBut quoteChar

type RAVOrder a = (Forest PlyData -> a) -> Forest PlyData -> [a]

breadthFirst, depthFirst :: RAVOrder a
breadthFirst _ [] = []
breadthFirst f ts = pure $ f ts
depthFirst f = fmap $ f . pure

pgnDoc :: RAVOrder (Doc ann) -> PGN -> Doc ann
pgnDoc ro (PGN games) = vsep $ gameDoc ro <$> games

gameDoc :: RAVOrder (Doc ann) -> Game -> Doc ann
gameDoc ro (tl, mt)
  | null tl = moveDoc ro pos mt
  | otherwise = tagsDoc tl <> line <> line <> moveDoc ro pos mt
 where
  pos | Just fen <- lookup "FEN" tl = fromJust $ fromFEN (T.unpack fen)
      | otherwise = startpos

tagsDoc :: [(ByteString, Text)] -> Doc ann
tagsDoc = vsep . fmap tagpair where
  tagpair (k, esc -> v) = brackets $ pretty (BS.unpack k) <+> dquotes (pretty v)
  esc = T.concatMap e where
    e '\\' = T.pack "\\\\"
    e '"' = T.pack "\\\""
    e c = T.singleton c

moveDoc :: RAVOrder (Doc ann) -> Position -> (Outcome, Forest PlyData) -> Doc ann
moveDoc ro pos (o,ts) = (fillSep $ go pos True ts <> [pretty o]) <> line where
  go _ _ [] = []
  go pos pmn (t:ts)
    | color pos == White || pmn
    = pnag <> (mn:san:snag) <> rav <> go pos' (not . null $ rav) (subForest t)
    | otherwise
    = pnag <> (san:snag) <> rav <> go pos' (not . null $ rav) (subForest t)
   where
    pl = ply . rootLabel $ t
    san = pretty $ unsafeToSAN pos pl
    pos' = unsafeDoPly pos pl
    pnag = nag <$> prefixNAG (rootLabel t)
    mn = pretty (moveNumber pos) <> if color pos == White then "." else "..."
    rav = ro (parens . fillSep . go pos True) ts
    snag = nag <$> suffixNAG (rootLabel t)
  nag n = "$" <> pretty n