{-# LANGUAGE GeneralizedNewtypeDeriving #-}

module AgdaHighlight
    ( highlightAgdaAsXHtml
--    , FormatOption (..)
    ) where

import Text.Highlighting.Kate as Kate
import Text.Blaze.Renderer.String

import Control.Monad.State
import System.IO.Unsafe

import Agda.Syntax.Literal
import Agda.Syntax.Position
import Agda.Syntax.Parser
import Agda.Syntax.Parser.Tokens (Token(..))

highlightAgdaAsXHtml :: String -> String
highlightAgdaAsXHtml code = formattedCode
    where
        language              = "agda"
        (Right highlightInfo) = highlight code
        formattedCode         = renderHtml $ formatHtmlBlock defaultFormatOpts highlightInfo

-- | Highlight source code using this syntax definition.
highlight :: String -> Either String [SourceLine]
highlight input = Right $ runSourceLineGen $ do
  tokens <- liftIO $ parse tokensParser input
  -- tokens :: IO [Tokens]
  -- Other parsing method needed - or unsafePerformIO
  -- map tokenToSourceLine tokens
  mapM_ processToken tokens
  where
--    processToken :: Token -> SourceLineGen ()
    processToken token =
        case token of
            TokKeyword kw iv     -> addByInterval (KeywordTok, getSourceByInterval iv) iv -- kw
            TokId (iv, id)       -> addByInterval (DataTypeTok, getSourceByInterval iv) iv -- dt
            TokQId ivds          -> mapM_ (\(iv, id) -> addByInterval (DataTypeTok, getSourceByInterval iv) iv) ivds -- dt
            TokLiteral lit       ->
                case lit of
                    LitInt r i      -> addByRange (DecValTok,  getSourceByRange r) r -- dv
                    LitFloat r d    -> addByRange (FloatTok,   getSourceByRange r) r -- fl
                    LitString r str -> addByRange (StringTok,  getSourceByRange r) r -- st
                    LitChar r ch    -> addByRange (CharTok,    getSourceByRange r) r -- ch
                    LitQName r qn   -> addByRange (OtherTok,   getSourceByRange r) r -- ?
            TokSymbol sym iv     -> addByInterval (FunctionTok, getSourceByInterval iv) iv -- TODO: switch by symbol?
            TokString (iv, str)  -> addByInterval (StringTok,  getSourceByInterval iv) iv -- st
            TokSetN (iv, n)      -> addByInterval (OtherTok,   "TokSetN") iv   -- ?
            TokTeX (iv, str)     -> addByInterval (OtherTok,   "TokTex") iv    -- ?
            TokComment (iv, str) -> addByInterval (CommentTok, getSourceByInterval iv) iv -- co
            TokDummy             -> return ()
            TokEOF               -> return ()
    
    getSourceByInterval :: Interval -> String
    getSourceByInterval iv = take len $ drop (st - 1) input
        where
            st  = (fromIntegral . posPos . iStart) iv
            end = (fromIntegral . posPos . iEnd) iv
            len = end - st
    
    getSourceByRange :: Range -> String
    getSourceByRange (Range ivs) = foldl (++) [] $ map getSourceByInterval ivs

type LabeledSource = Kate.Token -- ([String], String)

data SourceLineState = SLS
    { slsLines :: [SourceLine]
    , slsCurrentLine :: !Int
    , slsCurrentChar :: !Int
    } deriving (Show)

newtype SourceLineGen a = SLG (StateT SourceLineState IO a)
    deriving (Monad, MonadState SourceLineState, MonadIO)

newLine :: SourceLineGen ()
newLine = modify (\s -> s
    { slsLines = (slsLines s) ++ [[]]
    , slsCurrentLine = (slsCurrentLine s) + 1
    , slsCurrentChar = 1
    })

extendCurrentLine :: LabeledSource -> SourceLineGen ()
extendCurrentLine ls@(attrs, source) = modify (\s -> s { slsLines = modLines s, slsCurrentChar = modChars s })
    where
        modChars s = (slsCurrentChar s) + (length source)
        modLines s = (start s) ++ [ modLine s ] ++ (end s)
        modLine  s = ((slsLines s) !! ((slsCurrentLine s) - 1)) ++ [ ls ]
        start    s = fst $ parts s
        end      s = drop 1 $ snd $ parts s
        parts    s = splitAt ((slsCurrentLine s) - 1) (slsLines s)

addAt :: LabeledSource -> Int -> Int -> SourceLineGen ()
addAt ls line char = do
    currentLine <- gets slsCurrentLine
    let lineDiff = line - currentLine - 1
    mapM_ (\x -> newLine) [0..lineDiff]
    currentChar <- gets slsCurrentChar
    let charDiff = char - currentChar
    if charDiff > 0 then extendCurrentLine $ spaceLS charDiff else return ()
    extendCurrentLine ls
    where
        spaceLS n = (OtherTok, replicate n ' ')

addAtPosition :: LabeledSource -> Position -> SourceLineGen ()
addAtPosition ls p = addAt ls (fromIntegral $ posLine p) (fromIntegral $ posCol p)

addByInterval :: LabeledSource -> Interval -> SourceLineGen ()
addByInterval ls i = addAtPosition ls (iStart i)

addByRange :: LabeledSource -> Range -> SourceLineGen ()
addByRange ls (Range is) = mapM_ (addByInterval ls) is

runSourceLineGen :: SourceLineGen a -> [SourceLine]
runSourceLineGen (SLG body) = slsLines $ unsafePerformIO $ execStateT body (SLS
    { slsLines = [[]]
    , slsCurrentLine = 1
    , slsCurrentChar = 1
    })