-- -*- Haskell -*-

-- | The include file for alex-generated syntax highlighters.  Because alex
-- declares its own types, any wrapper must have the highlighter in scope...
-- so it must be included.  Doubleplusyuck.
--
-- You will need to import qualified Yi.Vty, and Yi.Syntax.
--
-- You will need to define initState and stateToInit and type HlState
--
-- Your actions must have type String -> $state -> ($state, [Attr])

type AlexInput  = LB.ByteString
type Action a   = AlexInput -> a -> (a, AlexResult)
type AlexState  = (AlexInput, HlState)
type AlexResult = [ (Int, Style) ]

alexGetChar :: AlexInput -> Maybe (Char, AlexInput)
alexGetChar bs | LB.null bs = Nothing
               | otherwise  = Just ( LB.head bs
                                   , LB.tail bs
                                   )

alexInputPrevChar = undefined

c :: Style -> Action a
c color str state = (state, [(fromIntegral $ LB.length str, color)])

m :: (s -> s) -> Style -> Action s
m mod color str state = (mod state, [(fromIntegral $ LB.length str, color)])

highlighter :: Yi.Syntax.Highlighter AlexState
highlighter = 
  Yi.Syntax.SynHL { Yi.Syntax.hlStartState   = startState
                  , Yi.Syntax.hlColorize     = fun
                  , Yi.Syntax.hlColorizeEOF  = funEOF
                  }
  where
  startState         = ( LB.empty, initState )
  fun :: AlexInput -> AlexState -> (AlexState, AlexResult)
  fun bs (scrap, st) = 
    iter' hl_alex_scan_tkn full st
    where
    full = LB.append scrap bs


  funEOF :: AlexState -> AlexResult
  funEOF (scrap, st) = 
    snd $ iter' alex_scan_tkn scrap st

  iter' :: ScanFun -> AlexInput -> HlState -> (AlexState, AlexResult)
  iter' scanFun bs s =
    case lastAction of
      (AlexNone, _)                -> ((bs, s), [])
      (AlexLastSkip _ _, _)        -> error "no skipping!"
      (AlexLastAcc k input len, _) -> 
        ( (str', finst), attrs ++ fattr )
        where
        (nst, attrs)           = k (LB.take (fromIntegral len) bs) s
        ((str', finst), fattr) = iter' scanFun input nst
    where 
    lastAction = scanFun undefined bs 0# bs start AlexNone
    start      = iUnbox (stateToInit s)

type ScanFun = Bool 
            -> AlexInput 
            -> (Int#)
            -> AlexInput 
            -> (Int#)
            -> AlexLastAcc KFun
            -> ( AlexLastAcc KFun, AlexInput )

type KFun = AlexInput -> HlState -> ( HlState, AlexResult)


-- Push the input through the DFA, remembering the most recent accepting
-- state it encountered.

-- Since the documented interface is insufficiently expressive, we have to use
-- the undocumented one :(

-- Our interface parses a token, but only if it is certain that the token is
-- the longest given available data.

hl_alex_scan_tkn :: ScanFun
hl_alex_scan_tkn user orig_input len input s last_acc =
  input `seq` -- strict in the input
  case s of
    -1# -> (last_acc, input)
    _   -> hl_alex_scan_tkn' user orig_input len input s last_acc

hl_alex_scan_tkn' :: ScanFun
hl_alex_scan_tkn' user orig_input len input s last_acc =
  new_acc `seq`
  case alexGetChar input of
    Nothing             -> (AlexNone, input) -- fail on EOF - important!
    Just (c, new_input) ->
      hl_alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc
      where
      base   = alexIndexInt32OffAddr alex_base s
      (I# (ord_c)) = ord c
      offset = (base +# ord_c)
      check  = alexIndexInt16OffAddr alex_check offset
        
      new_s
        | (offset >=# 0#) && (check ==# ord_c) =
          alexIndexInt16OffAddr alex_table offset
        | otherwise                            =
          alexIndexInt16OffAddr alex_deflt s
      


  where
  new_acc = check_accs (alex_accept `quickIndex` (I# (s)))

  check_accs []                             = last_acc
  check_accs (AlexAcc a : _)                = AlexLastAcc a input (I# (len))
  check_accs (AlexAccSkip : _)              = AlexLastSkip  input (I# (len))
  check_accs (AlexAccPred a pred : rest)
    | pred user orig_input (I# (len)) input =  AlexLastAcc a input (I# (len))
  check_accs (AlexAccSkipPred pred : rest)
    | pred user orig_input (I# (len)) input =  AlexLastSkip input (I# (len))
  check_accs (_ : rest) = check_accs rest