{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE FlexibleContexts #-}
module PDF.Text {-(
    pageContents
  )-} where

import Control.Applicative ((<|>))
import Control.Monad (foldM)
import Control.Monad.Fail (MonadFail)
import Control.Monad.Reader (ReaderT, runReaderT, asks)
import Control.Monad.State (MonadState, evalStateT, get, modify, put)
import Data.Attoparsec.ByteString.Char8 (choice, sepBy)
import Data.ByteString (ByteString)
import Data.ByteString.Char8 (pack, unpack)
import Data.Char (toLower)
import Data.Map ((!), (!?), Map)
import qualified Data.Map as Map (fromList)
import Data.Text (Text)
import PDF.Font (Font, FontSet, emptyFont)
import PDF.Object (
      DirectObject(..), StringObject(..)
    , array, blank, name, regular, stringObject, toByteString
  )
import PDF.Parser (MonadParser(..), (<?>), Parser, evalParser)

data StateOperator =
  C_m | W_ | J | J_ | M | D_ | R_i | I_ | G_s -- general graphic state
  deriving (Bounded, Enum, Show)
data PathOperator =
    M_ | L_ | C_ | V_ | Y_ | H_ | R_e -- path construction
  | S | S_ | F_ | F | Fstar | B | Bstar | B_ | B_star | N_ -- path painting
  | W | Wstar -- clipping path
  deriving (Bounded, Enum, Show)
data ColorOperator =
    CS | C_s | SC | SCN | S_c | S_cn | G | G_ | RG | R_g | K | K_
  deriving (Bounded, Enum, Show)
data TextOperator =
    Td | TD | Tm | Tstar -- text positioning
  | TJ | Tj | Quote | DQuote -- text showing
  | Tc | Tw | Tz | TL | Tf | Tr | Ts -- text state
  deriving (Bounded, Enum, Show)
data Argument = Raw ByteString | Typed DirectObject deriving Show
type Call a = (a, [Argument])

type Operator a = (Bounded a, Enum a, Show a)

code :: Operator a => a -> ByteString
code = pack . expand . show
  where
    expand "" = ""
    expand (c:'_':s) = toLower c : expand s
    expand ('s':'t':'a':'r':s) = '*' : expand s
    expand ('Q':'u':'o':'t':'e':s) = '\'' : expand s
    expand ('D':'Q':'u':'o':'t':'e':s) = '"' : expand s
    expand (c:s) = c : expand s

{-
instance Show StateOperator where
  show Cm = "cm"
  show W_ = "w"
  show J = "J"
  show J_ = "j"
  show M = "M"
  show D = "d"
  show Ri = "ri"
  show I = "i"
  show Gs = "gs"

instance Show PathOperator where
  show M_ = "m"
  show L_ = "l"
  show C_ = "c"
  show V_ = "v"
  show Y_ = "y"
  show H_
      ("m", (M_, \l -> case l of [Raw _, Raw _] -> True ; _ -> False))
    , ("l", (L_, \l -> case l of [Raw _, Raw _] -> True ; _ -> False))
    , ("c", (L_, \l -> case l of [Raw _, Raw _, Raw _, Raw _, Raw _, Raw _] -> True ; _ -> False))
    , ("v", (L_, \l -> case l of [Raw _, Raw _, Raw _, Raw _] -> True ; _ -> False))
    , ("y", (L_, \l -> case l of [Raw _, Raw _, Raw _, Raw _] -> True ; _ -> False))
    , ("h", (L_, \l -> case l of [] -> True ; _ -> False))
    , ("re", (L_, \l -> case l of [Raw _, Raw _, Raw _, Raw _] -> True ; _ -> False))
    , ("S", (L_, \l -> case l of [] -> True ; _ -> False))
    , ("s", (L_, \l -> case l of [] -> True ; _ -> False))
    , ("f", (L_, \l -> case l of [] -> True ; _ -> False))
    , ("F", (L_, \l -> case l of [] -> True ; _ -> False))
    , ("F*", (L_, \l -> case l of [] -> True ; _ -> False))
    , ("B", (L_, \l -> case l of [] -> True ; _ -> False))
    , ("B*", (L_, \l -> case l of [] -> True ; _ -> False))
    , ("b", (L_, \l -> case l of [] -> True ; _ -> False))
    , ("b*", (L_, \l -> case l of [] -> True ; _ -> False))
    , ("n", (L_, \l -> case l of [] -> True ; _ -> False))
    , ("W", (L_, \l -> case l of [] -> True ; _ -> False))
    , ("W*", (L_, \l -> case l of [] -> True ; _ -> False))

instance Show ColorOperator where

instance Show TextOperator where
  show Td = "Td"
  show TD = "TD"
  show Tm = "Tm"
  show Tstar = "T*"
  show TJ = "TJ"
  show Tj = "Tj"
  show Quote = "'"
  show DQuote = "\""
  show Tc = "Tc"
  show Tw = "Tw"
  show Tz = "Tz"
  show TL = "TL"
  show Tf = "Tf"
  show Tr = "Tr"
  show Ts = "Ts"
-}

stateOperator :: OperatorTable StateOperator
stateOperator = Map.fromList $ (\(op, checker) -> (code op, (op, checker))) <$> [
      (C_m, \l -> case l of [Raw _, Raw _, Raw _, Raw _, Raw _, Raw _] -> True ; _ -> False)
    , (W_, \l -> case l of [Raw _] -> True ; _ -> False)
    , (J, \l -> case l of [Raw _] -> True ; _ -> False)
    , (J_, \l -> case l of [Raw _] -> True ; _ -> False)
    , (M, \l -> case l of [Raw _] -> True ; _ -> False)
    , (D_, \l -> case l of [Raw _, Raw _] -> True ; _ -> False)
    , (R_i, \l -> case l of [Raw _] -> True ; _ -> False)
    , (I_, \l -> case l of [Raw _] -> True ; _ -> False)
    , (G_s, \l -> case l of [Typed (NameObject _)] -> True ; _ -> False)
  ]

pathOperator :: OperatorTable PathOperator
pathOperator = Map.fromList $ (\(op, checker) -> (code op, (op, checker))) <$> [
      (M_, \l -> case l of [Raw _, Raw _] -> True ; _ -> False)
    , (L_, \l -> case l of [Raw _, Raw _] -> True ; _ -> False)
    , (C_, \l -> case l of [Raw _, Raw _, Raw _, Raw _, Raw _, Raw _] -> True ; _ -> False)
    , (V_, \l -> case l of [Raw _, Raw _, Raw _, Raw _] -> True ; _ -> False)
    , (Y_, \l -> case l of [Raw _, Raw _, Raw _, Raw _] -> True ; _ -> False)
    , (H_, \l -> case l of [] -> True ; _ -> False)
    , (R_e, \l -> case l of [Raw _, Raw _, Raw _, Raw _] -> True ; _ -> False)
    , (S, \l -> case l of [] -> True ; _ -> False)
    , (S_, \l -> case l of [] -> True ; _ -> False)
    , (F_, \l -> case l of [] -> True ; _ -> False)
    , (F, \l -> case l of [] -> True ; _ -> False)
    , (Fstar, \l -> case l of [] -> True ; _ -> False)
    , (B, \l -> case l of [] -> True ; _ -> False)
    , (Bstar, \l -> case l of [] -> True ; _ -> False)
    , (B_, \l -> case l of [] -> True ; _ -> False)
    , (B_star, \l -> case l of [] -> True ; _ -> False)
    , (N_, \l -> case l of [] -> True ; _ -> False)
    , (W, \l -> case l of [] -> True ; _ -> False)
    , (Wstar, \l -> case l of [] -> True ; _ -> False)
  ]

colorOperator :: OperatorTable ColorOperator
colorOperator = Map.fromList $ (\(op, checker) -> (code op, (op, checker))) <$> [
      (CS, \l -> case l of [Typed (NameObject _)] -> True ; _ -> False)
    , (C_s, \l -> case l of [Typed (NameObject _)] -> True ; _ -> False)
    , (SC, \_ -> True)
    , (SCN, \_ -> True)
    , (S_c, \_ -> True)
    , (S_cn, \_ -> True)
    , (G, \l -> case l of [Raw _] -> True ; _ -> False)
    , (G_, \l -> case l of [Raw _] -> True ; _ -> False)
    , (RG, \l -> case l of [Raw _, Raw _, Raw _] -> True ; _ -> False)
    , (R_g, \l -> case l of [Raw _, Raw _, Raw _] -> True ; _ -> False)
    , (K, \l -> case l of [Raw _, Raw _, Raw _, Raw _] -> True ; _ -> False)
    , (K_, \l -> case l of [Raw _, Raw _, Raw _, Raw _] -> True ; _ -> False)
  ]

{-
stateOperator (Cm, [Raw _, Raw _, Raw _, Raw _, Raw _, Raw _]) = True
stateOperator (W, [Raw _]) = True
stateOperator (J, [Raw _]) = True
stateOperator (J_, [Raw _]) = True
stateOperator (M, [Raw _]) = True
stateOperator (D, [Raw _, Raw _]) = True
stateOperator (Ri, [Raw _]) = True
stateOperator (I, [Raw _]) = True
stateOperator (Gs, [Typed (NameObject _)]) = True
stateOperator _ = False
-}

textOperator :: OperatorTable TextOperator
textOperator = Map.fromList $ (\(op, checker) -> (code op, (op, checker))) <$> [
      (Td, \l -> case l of [Raw _, Raw _] -> True ; _ -> False)
    , (TD, \l -> case l of [Raw _, Raw _] -> True ; _ -> False)
    , (Tm, \l -> case l of [Raw _, Raw _, Raw _, Raw _, Raw _, Raw _] -> True ; _ -> False)
    , (Tstar, \l -> case l of [] -> True ; _ -> False)
    , (TJ, \l -> case l of [Typed (Array _)] -> True ; _ -> False)
    , (Tj, \l -> case l of [Typed (StringObject _)] -> True ; _ -> False)
    , (Quote, \l -> case l of [Typed (StringObject _)] -> True ; _ -> False)
    , (DQuote, \l -> case l of [Typed (StringObject _)] -> True ; _ -> False)
    , (Tc, \l -> case l of [Raw _] -> True ; _ -> False)
    , (Tw, \l -> case l of [Raw _] -> True ; _ -> False)
    , (Tz, \l -> case l of [Raw _] -> True ; _ -> False)
    , (TL, \l -> case l of [Raw _] -> True ; _ -> False)
    , (Tf, \l -> case l of [Typed (NameObject _), Raw _] -> True ; _ -> False)
    , (Tr, \l -> case l of [Raw _] -> True ; _ -> False)
    , (Ts, \l -> case l of [Raw _] -> True ; _ -> False)
  ]

  {-
textOperator (Td, [Raw _, Raw _]) = True
textOperator (TD, [Raw _, Raw _]) = True
textOperator (Tm, [Raw _, Raw _, Raw _, Raw _, Raw _, Raw _]) = True
textOperator (Tstar, []) = True
textOperator (TJ, [Typed (Array _)]) = True
textOperator (Tj, [Typed (StringObject _)]) = True
textOperator (Quote, [Typed (StringObject _)]) = True
textOperator (DQuote, [Typed (StringObject _)]) = True
textOperator (Tc, [Raw _]) = True
textOperator (Tw, [Raw _]) = True
textOperator (Tz, [Raw _]) = True
textOperator (TL, [Raw _]) = True
textOperator (Tf, [Typed (NameObject _), Raw _]) = True
textOperator (Tr, [Raw _]) = True
textOperator (Ts, [Raw _]) = True
textOperator _ = False
-}

type ArgumentStackParser m = (MonadState [Argument] m, MonadParser m)
--type Operator a = (Bounded a, Enum a, Show a)
type OperatorTable a = Map ByteString (TypeChecker a)
type TypeChecker a = (a, [Argument] -> Bool)

parseShowable :: (Show a, MonadParser m) => a -> m a
parseShowable textOp = string (pack $ show textOp) *> return textOp

callChunk :: MonadParser m => OperatorTable a -> m (Either (TypeChecker a) Argument)
callChunk table =
    (Right <$> choice [stringArg, nameArg, arrayArg])
  <|> operatorOrRawArg
  <?> "call chunk"
  where
    operatorOrRawArg = do
      chunk <- takeAll1 regular <* blank
      case table !? chunk of
        Nothing -> return . Right $ Raw chunk
        Just typeChecker -> return $ Left typeChecker

stackParser :: (ArgumentStackParser m, Operator a) => OperatorTable a -> m (Call a)
stackParser table = either popCall push =<< (callChunk table)
  where
    push arg = modify (arg:) >> stackParser table
    popCall (operator, predicate) = do
      arguments <- reverse <$> get
      let call = (operator, arguments)
      if predicate arguments then return call else fail (unpack $ code operator)

a :: (Operator a, MonadParser m) => OperatorTable a -> m (Call a)
a table = evalStateT (stackParser table) []

argument :: MonadParser m => m Argument
argument = Raw <$> takeAll1 regular <* blank

arrayArg :: MonadParser m => m Argument
arrayArg = Typed . Array <$> array <* blank

nameArg :: MonadParser m => m Argument
nameArg = Typed . NameObject <$> name <* blank

stringArg :: MonadParser m => m Argument
stringArg = Typed . StringObject <$> stringObject <* blank

type ParserWithFont = ReaderT FontSet (Parser Font)

pageContents :: FontSet -> ByteString -> Either String [Text]
pageContents fontSet input =
  evalParser (runReaderT (page) fontSet) emptyFont input

several :: MonadParser m => m [a] -> m [a]
several p = concat <$> (p `sepBy` blank)

page :: ParserWithFont [Text]
page = several (graphicState <|> text) <* blank <* endOfInput <?> "Text page contents"

graphicState :: ParserWithFont [Text]
graphicState =
  string "q" *> blank *> insideQ <* blank <* string "Q" <?> "Graphic state"
  where
    insideQ = several (command <|> graphicState <|> text)
    ignore x = a x *> return []
    command =
      ignore stateOperator <|> ignore pathOperator <|> ignore colorOperator

text :: ParserWithFont [Text]
text =
  string "BT" *> blank *> commands <* blank <* string "ET" <?> "Text operators"
  where
    commands = several (a textOperator >>= runOperator)

runOperator :: Call TextOperator -> ParserWithFont [Text]
runOperator (Tf, [Typed (NameObject fontName), _]) =
  asks (! fontName) >>= put >> return []

runOperator (Tstar, []) = return ["\n"]

runOperator (TJ, [Typed (Array arrayObject)]) =
  replicate 1 <$> foldM appendText "" arrayObject
  where
    appendText bs (StringObject outputString) =
      mappend bs <$> decodeString outputString
    appendText bs _ = return bs

runOperator (Tj, [Typed (StringObject outputString)]) =
  replicate 1 <$> decodeString outputString

runOperator (Quote, [Typed (StringObject outputString)]) =
  (\bs -> ["\n", bs]) <$> decodeString outputString

runOperator (DQuote, [Typed (StringObject outputString)]) =
  (\bs -> ["\n", bs]) <$> decodeString outputString

runOperator _ = return []

decodeString :: (MonadFail m, MonadState Font m) => StringObject -> m Text
decodeString input = do
  font <- get
  either fail return . font $ toByteString input