{-# LANGUAGE InstanceSigs, RankNTypes, ScopedTypeVariables, TypeFamilies #-}
-- | Continuation-passing parser for context-free grammars
module Text.Grampa.ContextFree.Continued (Parser(..), Result(..), alt) where

import Control.Applicative (Applicative(..), Alternative(..), liftA2)
import Control.Monad (Monad(..), MonadPlus(..))

import Data.Char (isSpace)
import Data.Functor.Classes (Show1(..))
import Data.Functor.Compose (Compose(..))
import Data.List (nub)
import Data.Monoid (Monoid(mappend, mempty), (<>))
import Data.Monoid.Factorial(FactorialMonoid)
import Data.Monoid.Textual(TextualMonoid)
import Data.String (fromString)

import qualified Data.Monoid.Cancellative as Cancellative
import qualified Data.Monoid.Factorial as Factorial
import qualified Data.Monoid.Null as Null
import qualified Data.Monoid.Textual as Textual

import qualified Rank2

import qualified Text.Parser.Char
import Text.Parser.Char (CharParsing)
import Text.Parser.Combinators (Parsing(..))
import Text.Parser.LookAhead (LookAheadParsing(..))
import Text.Parser.Token (TokenParsing(someSpace))
import Text.Grampa.Class (MonoidParsing(..), MultiParsing(..), ParseResults, ParseFailure(..))
import Text.Grampa.Internal (FailureInfo(..))

data Result (g :: (* -> *) -> *) s v = Parsed{parsedPrefix :: !v,
                                              parsedSuffix :: !s}
                                     | NoParse FailureInfo

-- | Parser type for context-free grammars that uses a continuation-passing algorithm, fast for grammars in LL(1)
-- class but with potentially exponential performance for longer ambiguous prefixes.
newtype Parser (g :: (* -> *) -> *) s r =
   Parser{applyParser :: forall x. s -> (r -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x}

instance Show1 (Result g s) where
   liftShowsPrec showsPrecSub _showList prec Parsed{parsedPrefix= r} rest = "Parsed " ++ showsPrecSub prec r rest
   liftShowsPrec _showsPrec _showList _prec (NoParse f) rest = "NoParse " ++ shows f rest

instance Functor (Result g s) where
   fmap f (Parsed a rest) = Parsed (f a) rest
   fmap _ (NoParse failure) = NoParse failure
   
instance Functor (Parser g s) where
   fmap f (Parser p) = Parser (\input success-> p input (success . f))
   {-# INLINABLE fmap #-}

instance Applicative (Parser g s) where
   pure a = Parser (\input success failure-> success a input failure)
   (<*>) :: forall a b. Parser g s (a -> b) -> Parser g s a -> Parser g s b
   Parser p <*> Parser q = Parser r where
      r :: forall x. s -> (b -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
      r rest success failure = p rest (\f rest'-> q rest' (success . f)) failure
   {-# INLINABLE (<*>) #-}

instance Factorial.FactorialMonoid s => Alternative (Parser g s) where
   empty = Parser (\rest _ failure-> failure $ FailureInfo 0 (fromIntegral $ Factorial.length rest) ["empty"])
   (<|>) = alt

-- | A named and unconstrained version of the '<|>' operator
alt :: forall g s a. Parser g s a -> Parser g s a -> Parser g s a
Parser p `alt` Parser q = Parser r where
   r :: forall x. s -> (a -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
   r rest success failure = p rest success' failure'
      where success' a rest' _ = success a rest' failure'
            failure' f1 = q rest success (\f2 -> failure (f1 <> f2))

instance Monad (Parser g s) where
   return = pure
   (>>=) :: forall a b. Parser g s a -> (a -> Parser g s b) -> Parser g s b
   Parser p >>= f = Parser r where
      r :: forall x. s -> (b -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
      r rest success failure = p rest (\a rest'-> applyParser (f a) rest' success) failure

instance Factorial.FactorialMonoid s => MonadPlus (Parser g s) where
   mzero = empty
   mplus = (<|>)

instance Monoid x => Monoid (Parser g s x) where
   mempty = pure mempty
   mappend = liftA2 mappend

instance Factorial.FactorialMonoid s => Parsing (Parser g s) where
   try = id
   (<?>) = const
   eof = endOfInput
   unexpected msg = Parser (\t _ failure -> failure $ FailureInfo 0 (fromIntegral $ Factorial.length t) [msg])
   notFollowedBy (Parser p) = Parser q
      where q :: forall x. s -> (() -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            q input success failure = p input success' failure'
               where success' _ _ _ = failure (FailureInfo 1 (fromIntegral $ Factorial.length input) ["notFollowedBy"])
                     failure' _ = success () input failure

instance Factorial.FactorialMonoid s => LookAheadParsing (Parser g s) where
   lookAhead :: forall a. Parser g s a -> Parser g s a
   lookAhead (Parser p) = Parser q
      where q :: forall x. s -> (a -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            q input success failure = p input success' failure'
               where success' a _ = success a input
                     failure' f = failure f

instance (Show s, TextualMonoid s) => CharParsing (Parser g s) where
   satisfy = satisfyChar
   string s = Textual.toString (error "unexpected non-character") <$> string (fromString s)
   char = satisfyChar . (==)
   notChar = satisfyChar . (/=)
   anyChar = satisfyChar (const True)
   text t = (fromString . Textual.toString (error "unexpected non-character")) <$> string (Textual.fromText t)

instance (Show s, TextualMonoid s) => TokenParsing (Parser g s) where
   someSpace = () <$ takeCharsWhile1 isSpace

instance MonoidParsing (Parser g) where
   endOfInput = Parser p
      where p rest success failure
               | Null.null rest = success () rest failure
               | otherwise = failure (FailureInfo 1 (fromIntegral $ Factorial.length rest) ["endOfInput"])
   getInput = Parser p
      where p rest success failure = success rest mempty failure
   anyToken = Parser p
      where p rest success failure =
               case Factorial.splitPrimePrefix rest
               of Just (first, suffix) -> success first suffix failure
                  _ -> failure (FailureInfo 1 (fromIntegral $ Factorial.length rest) ["anyToken"])
   satisfy :: forall s. FactorialMonoid s => (s -> Bool) -> Parser g s s
   satisfy predicate = Parser p
      where p :: forall x. s -> (s -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            p rest success failure =
               case Factorial.splitPrimePrefix rest
               of Just (first, suffix) | predicate first -> success first suffix failure
                  _ -> failure (FailureInfo 1 (fromIntegral $ Factorial.length rest) ["satisfy"])
   satisfyChar :: forall s. TextualMonoid s => (Char -> Bool) -> Parser g s Char
   satisfyChar predicate = Parser p
      where p :: forall x. s -> (Char -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            p rest success failure =
               case Textual.splitCharacterPrefix rest
               of Just (first, suffix) | predicate first -> success first suffix failure
                  _ -> failure (FailureInfo 1 (fromIntegral $ Factorial.length rest) ["satisfyChar"])
   satisfyCharInput :: forall s. TextualMonoid s => (Char -> Bool) -> Parser g s s
   satisfyCharInput predicate = Parser p
      where p :: forall x. s -> (s -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            p rest success failure =
               case Textual.splitCharacterPrefix rest
               of Just (first, suffix) | predicate first -> success (Factorial.primePrefix rest) suffix failure
                  _ -> failure (FailureInfo 1 (fromIntegral $ Factorial.length rest) ["satisfyChar"])
   notSatisfy :: forall s. FactorialMonoid s => (s -> Bool) -> Parser g s ()
   notSatisfy predicate = Parser p
      where p :: forall x. s -> (() -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            p rest success failure =
               case Factorial.splitPrimePrefix rest
               of Just (first, _)
                     | predicate first -> failure (FailureInfo 1 (fromIntegral $ Factorial.length rest) ["notSatisfy"])
                  _ -> success () rest failure
   notSatisfyChar :: forall s. TextualMonoid s => (Char -> Bool) -> Parser g s ()
   notSatisfyChar predicate = Parser p
      where p :: forall x. s -> (() -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            p rest success failure =
               case Textual.characterPrefix rest
               of Just first | predicate first
                               -> failure (FailureInfo 1 (fromIntegral $ Factorial.length rest) ["notSatisfyChar"])
                  _ -> success () rest failure
   scan :: forall t s. FactorialMonoid t => s -> (s -> t -> Maybe s) -> Parser g t t
   scan s0 f = Parser (p s0)
      where p :: forall x. s -> t -> (t -> t -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            p s rest success failure = success prefix suffix failure
               where (prefix, suffix, _) = Factorial.spanMaybe' s f rest
   scanChars :: forall t s. TextualMonoid t => s -> (s -> Char -> Maybe s) -> Parser g t t
   scanChars s0 f = Parser (p s0)
      where p :: forall x. s -> t -> (t -> t -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            p s rest success failure = success prefix suffix failure
               where (prefix, suffix, _) = Textual.spanMaybe_' s f rest
   takeWhile :: forall s. FactorialMonoid s => (s -> Bool) -> Parser g s s
   takeWhile predicate = Parser p
      where p :: forall x. s -> (s -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            p rest success failure | (prefix, suffix) <- Factorial.span predicate rest = success prefix suffix failure
   takeWhile1 :: forall s. FactorialMonoid s => (s -> Bool) -> Parser g s s
   takeWhile1 predicate = Parser p
      where p :: forall x. s -> (s -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            p rest success failure
               | (prefix, suffix) <- Factorial.span predicate rest =
                    if Null.null prefix
                    then failure (FailureInfo 1 (fromIntegral $ Factorial.length rest) ["takeWhile1"])
                    else success prefix suffix failure
   takeCharsWhile :: forall s. TextualMonoid s => (Char -> Bool) -> Parser g s s
   takeCharsWhile predicate = Parser p
      where p :: forall x. s -> (s -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            p rest success failure
               | (prefix, suffix) <- Textual.span_ False predicate rest = success prefix suffix failure
   takeCharsWhile1 :: forall s. TextualMonoid s => (Char -> Bool) -> Parser g s s
   takeCharsWhile1 predicate = Parser p
      where p :: forall x. s -> (s -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            p rest success failure
               | Null.null prefix = failure (FailureInfo 1 (fromIntegral $ Factorial.length rest) ["takeCharsWhile1"])
               | otherwise = success prefix suffix failure
               where (prefix, suffix) = Textual.span_ False predicate rest
   string :: forall s. (Cancellative.LeftReductiveMonoid s, FactorialMonoid s, Show s) => s -> Parser g s s
   string s = Parser p where
      p :: forall x. s -> (s -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
      p s' success failure
         | Just suffix <- Cancellative.stripPrefix s s' = success s suffix failure
         | otherwise = failure (FailureInfo 1 (fromIntegral $ Factorial.length s') ["string " ++ show s])
   whiteSpace = () <$ takeCharsWhile isSpace
   concatMany :: forall s a. Monoid a => Parser g s a -> Parser g s a
   concatMany (Parser p) = Parser q
      where q :: forall x. s -> (a -> s -> (FailureInfo -> x) -> x) -> (FailureInfo -> x) -> x
            q rest success failure = p rest success' (const $ success mempty rest failure)
               where success' prefix suffix failure' =
                        q suffix (success . (prefix <>)) (const $ success prefix suffix failure')
   {-# INLINABLE string #-}

-- | Continuation-passing context-free parser
--
-- @
-- 'parseComplete' :: ("Rank2".'Rank2.Functor' g, 'FactorialMonoid' s) =>
--                  g (Continued.'Parser' g s) -> s -> g 'ParseResults'
-- @
instance MultiParsing Parser where
   type ResultFunctor Parser = ParseResults
   -- | Returns an input prefix parse paired with the remaining input suffix.
   parsePrefix g input = Rank2.fmap (Compose . (\p-> applyParser p input (\a rest _-> Right (rest, a)) (Left . fromFailure input))) g
   parseComplete g input = Rank2.fmap (\p-> applyParser p input (const . const . Right) (Left . fromFailure input))
                                      (Rank2.fmap (<* endOfInput) g)

fromFailure :: FactorialMonoid s => s -> FailureInfo -> ParseFailure
fromFailure s (FailureInfo _ pos msgs) = ParseFailure (Factorial.length s - fromIntegral pos + 1) (nub msgs)