{-# LANGUAGE BangPatterns, CPP, FlexibleContexts, GeneralizedNewtypeDeriving, InstanceSigs,
             RankNTypes, ScopedTypeVariables, TypeFamilies, TypeOperators, UndecidableInstances #-}
-- | A context-free memoizing parser that handles all alternatives in parallel.
module Text.Grampa.ContextFree.SortedMemoizing 
       (ParseFailure(..), ResultList(..), Parser(..),
        longest, peg, terminalPEG)
where

import Control.Applicative
import Control.Monad (Monad(..), MonadPlus(..))
#if MIN_VERSION_base(4,13,0)
import Control.Monad (MonadFail(fail))
#endif
import Data.Either (partitionEithers)
import Data.Functor.Compose (Compose(..))
import Data.List (intercalate)
import Data.List.NonEmpty (NonEmpty((:|)), nonEmpty, toList)
import Data.Monoid (Monoid(mappend, mempty))
import Data.Monoid.Null (MonoidNull(null))
import Data.Monoid.Factorial (FactorialMonoid, splitPrimePrefix)
import Data.Monoid.Textual (TextualMonoid)
import qualified Data.Monoid.Factorial as Factorial
import qualified Data.Monoid.Textual as Textual
import Data.Ord (Down(Down))
import Data.Semigroup (Semigroup((<>)))
import Data.Semigroup.Cancellative (LeftReductive(isPrefixOf))
import Data.String (fromString)
import Debug.Trace (trace)
import Witherable (Filterable(mapMaybe))

import qualified Text.Parser.Char
import Text.Parser.Char (CharParsing)
import Text.Parser.Combinators (Parsing(..))
import Text.Parser.Input.Position (fromEnd)
import Text.Parser.LookAhead (LookAheadParsing(..))

import qualified Rank2

import Text.Grampa.Class (GrammarParsing(..), InputParsing(..), InputCharParsing(..), MultiParsing(..),
                          AmbiguousParsing(..), Ambiguous(Ambiguous), CommittedParsing(..),
                          ConsumedInputParsing(..), DeterministicParsing(..),
                          TailsParsing(parseTails, parseAllTails), ParseResults, ParseFailure(..),
                          FailureDescription(..))
import Text.Grampa.Internal (ResultList(..), ResultsOfLength(..), TraceableParsing(..),
                             emptyFailure, expected, expectedInput, replaceExpected, erroneous)
import qualified Text.Grampa.PEG.Backtrack.Measured as Backtrack

import Prelude hiding (iterate, null, showList, span, takeWhile)

-- | Parser for a context-free grammar with packrat-like sharing of parse results. It does not support left-recursive
-- grammars.
newtype Parser g s r = Parser{applyParser :: [(s, g (ResultList g s))] -> ResultList g s r}

instance Functor (Parser g i) where
   fmap f (Parser p) = Parser (fmap f . p)
   {-# INLINE fmap #-}

instance Ord s => Applicative (Parser g s) where
   pure a = Parser (\rest-> ResultList [ResultsOfLength 0 rest (a:|[])] mempty)
   Parser p <*> Parser q = Parser r where
      r rest = case p rest
               of ResultList results failure -> ResultList mempty failure <> foldMap continue results
      continue (ResultsOfLength l rest' fs) = foldMap (continue' l $ q rest') fs
      continue' l (ResultList rs failure) f = ResultList (adjust l f <$> rs) failure
      adjust l f (ResultsOfLength l' rest' as) = ResultsOfLength (l+l') rest' (f <$> as)
   {-# INLINABLE pure #-}
   {-# INLINABLE (<*>) #-}

instance Ord s => Alternative (Parser g s) where
   empty = Parser (ResultList mempty . emptyFailure . Down . length)
   Parser p <|> Parser q = Parser r where
      r rest = p rest <> q rest
   {-# INLINE (<|>) #-}
   {-# INLINABLE empty #-}

instance Filterable (Parser g s) where
  mapMaybe f (Parser p) = Parser (mapMaybe f . p)

instance Ord s => Monad (Parser g s) where
   return = pure
   (>>) = (*>)
   Parser p >>= f = Parser q where
      q rest = case p rest
               of ResultList results failure -> ResultList mempty failure <> foldMap continue results
      continue (ResultsOfLength l rest' rs) = foldMap (continue' l . flip applyParser rest' . f) rs
      continue' l (ResultList rs failure) = ResultList (adjust l <$> rs) failure
      adjust l (ResultsOfLength l' rest' rs) = ResultsOfLength (l+l') rest' rs

#if MIN_VERSION_base(4,13,0)
instance Ord s => MonadFail (Parser g s) where
#endif
   fail msg = Parser p
      where p rest = ResultList mempty (erroneous (Down $ length rest) msg)

instance Ord s => MonadPlus (Parser g s) where
   mzero = empty
   mplus = (<|>)

instance (Semigroup x, Ord s) => Semigroup (Parser g s x) where
   (<>) = liftA2 (<>)

instance (Monoid x, Ord s) => Monoid (Parser g s x) where
   mempty = pure mempty
   mappend = (<>)

-- | Memoizing parser guarantees O(n²) performance for grammars with unambiguous productions. Can be wrapped with
-- 'Text.Grampa.ContextFree.SortedMemoizing.LeftRecursive.Fixed' to provide left recursion support.
instance (Ord s, LeftReductive s, FactorialMonoid s) => GrammarParsing (Parser g s) where
   type ParserGrammar (Parser g s) = g
   type GrammarFunctor (Parser g s) = ResultList g s
   parsingResult _ = Compose . fromResultList
   nonTerminal :: (Rank2.Functor g, ParserInput (Parser g s) ~ s) => (g (ResultList g s) -> ResultList g s a) -> Parser g s a
   nonTerminal f = Parser p where
      p input@((_, d) : _) = ResultList rs' failure
         where ResultList rs failure = f d
               rs' = sync <$> rs
               -- in left-recursive grammars the stored input remainder may be wrong, so revert to the current input
               sync (ResultsOfLength 0 _remainder r) = ResultsOfLength 0 input r
               sync rol = rol
      p _ = ResultList mempty (expected 0 "NonTerminal at endOfInput")
   {-# INLINE nonTerminal #-}
   chainRecursive assign (Parser base) (Parser recurse) = Parser q
      where q [] = base []
            q ((s, d):t) = case base ((s, assign mempty d) : t)
                           of r@(ResultList [] _) -> r
                              r -> iter r r
               where iter marginal total = case recurse ((s, assign marginal d) : t)
                                           of ResultList [] _ -> total
                                              r -> iter r (total <> r)
   chainLongestRecursive assign (Parser base) (Parser recurse) = Parser q
      where q [] = base []
            q ((s, d):t) = case base ((s, assign mempty d) : t)
                           of r@(ResultList [] _) -> r
                              r -> iter r
               where iter r = case recurse ((s, assign r d) : t)
                              of ResultList [] _ -> r
                                 r' -> iter r'

instance (Ord s, LeftReductive s, FactorialMonoid s) => TailsParsing (Parser g s) where
   parseTails = applyParser

-- | Memoizing parser guarantees O(n²) performance for grammars with unambiguous productions. Can be wrapped with
-- 'Text.Grampa.ContextFree.SortedMemoizing.LeftRecursive.Fixed' to provide left recursion support.
--
-- @
-- 'parseComplete' :: ("Rank2".'Rank2.Functor' g, 'FactorialMonoid' s) =>
--                  g (Memoizing.'Parser' g s) -> s -> g ('Compose' ('ParseResults' s) [])
-- @
instance (LeftReductive s, FactorialMonoid s, Ord s) => MultiParsing (Parser g s) where
   type GrammarConstraint (Parser g s) g' = (g ~ g', Rank2.Functor g)
   type ResultFunctor (Parser g s) = Compose (ParseResults s) []
   -- | Returns the list of all possible input prefix parses paired with the remaining input suffix.
   parsePrefix g input = Rank2.fmap (Compose . Compose . fromResultList) (snd $ head $ parseGrammarTails g input)
   -- parseComplete :: (ParserInput (Parser g s) ~ s, Rank2.Functor g, Eq s, FactorialMonoid s) =>
   --                  g (Parser g s) -> s -> g (Compose (ParseResults s) [])
   parseComplete g input = Rank2.fmap ((snd <$>) . Compose . fromResultList)
                              (snd $ head $ parseAllTails close $ parseGrammarTails g input)
      where close = Rank2.fmap (<* eof) g

fromResultList :: FactorialMonoid s => ResultList g s r -> ParseResults s [(s, r)]
fromResultList (ResultList [] (ParseFailure pos expected' erroneous')) =
   Left (ParseFailure (pos - 1) expected' erroneous')
fromResultList (ResultList rl _failure) = Right (foldMap f rl)
   where f (ResultsOfLength _ ((s, _):_) r) = (,) s <$> toList r
         f (ResultsOfLength _ [] r) = (,) mempty <$> toList r

parseGrammarTails :: (Rank2.Functor g, FactorialMonoid s) => g (Parser g s) -> s -> [(s, g (ResultList g s))]
parseGrammarTails g input = foldr parseTail [] (Factorial.tails input)
   where parseTail s parsedTail = parsed
            where parsed = (s,d):parsedTail
                  d      = Rank2.fmap (($ parsed) . applyParser) g

instance (LeftReductive s, FactorialMonoid s, Ord s) => InputParsing (Parser g s) where
   type ParserInput (Parser g s) = s
   getInput = Parser p
      where p rest@((s, _):_) = ResultList [ResultsOfLength 0 rest (s:|[])] mempty
            p [] = ResultList [ResultsOfLength 0 [] (mempty:|[])] mempty
   anyToken = Parser p
      where p rest@((s, _):t) = case splitPrimePrefix s
                                of Just (first, _) -> ResultList [ResultsOfLength 1 t (first:|[])] mempty
                                   _ -> ResultList mempty (expected (Down $ length rest) "anyToken")
            p [] = ResultList mempty (expected 0 "anyToken")
   satisfy predicate = Parser p
      where p rest@((s, _):t) =
               case splitPrimePrefix s
               of Just (first, _) | predicate first -> ResultList [ResultsOfLength 1 t (first:|[])] mempty
                  _ -> ResultList mempty (expected (Down $ length rest) "satisfy")
            p [] = ResultList mempty (expected 0 "satisfy")
   scan s0 f = Parser (p s0)
      where p s rest@((i, _) : _) = ResultList [ResultsOfLength l (drop l rest) (prefix:|[])] mempty
               where (prefix, _, _) = Factorial.spanMaybe' s f i
                     l = Factorial.length prefix
            p _ [] = ResultList [ResultsOfLength 0 [] (mempty:|[])] mempty
   take 0 = mempty
   take n = Parser p
      where p rest@((s, _) : _)
               | x <- Factorial.take n s, l <- Factorial.length x, l == n =
                    ResultList [ResultsOfLength l (drop l rest) (x:|[])] mempty
            p rest = ResultList mempty (expected (Down $ length rest) $ "take " ++ show n)
   takeWhile predicate = Parser p
      where p rest@((s, _) : _)
               | x <- Factorial.takeWhile predicate s, l <- Factorial.length x =
                    ResultList [ResultsOfLength l (drop l rest) (x:|[])] mempty
            p [] = ResultList [ResultsOfLength 0 [] (mempty:|[])] mempty
   takeWhile1 predicate = Parser p
      where p rest@((s, _) : _)
               | x <- Factorial.takeWhile predicate s, l <- Factorial.length x, l > 0 =
                    ResultList [ResultsOfLength l (drop l rest) (x:|[])] mempty
            p rest = ResultList mempty (expected (Down $ length rest) "takeWhile1")
   string s = Parser p where
      p rest@((s', _) : _)
         | s `isPrefixOf` s' = ResultList [ResultsOfLength l (Factorial.drop l rest) (s:|[])] mempty
      p rest = ResultList mempty (expectedInput (fromEnd $ length rest) s)
      l = Factorial.length s
   notSatisfy predicate = Parser p
      where p rest@((s, _):_)
               | Just (first, _) <- splitPrimePrefix s, 
                 predicate first = ResultList mempty (expected (Down $ length rest) "notSatisfy")
            p rest = ResultList [ResultsOfLength 0 rest (():|[])] mempty
   {-# INLINABLE string #-}

instance (InputParsing (Parser g s), FactorialMonoid s) => TraceableParsing (Parser g s) where
   traceInput description (Parser p) = Parser q
      where q rest@((s, _):_) = case trace ("Parsing " <> description s) (p rest) of
               rl@(ResultList [] _) -> trace ("Failed " <> descriptionWith id) rl
               rl@(ResultList rs _) -> trace ("Parsed [" <> intercalate ", " (describeResult <$> rs) <> "]") rl
               where describeResult (ResultsOfLength len _ _) = descriptionWith (Factorial.take len)
                     descriptionWith f = description (f s)
            q [] = p []

instance (Ord s, Show s, TextualMonoid s) => InputCharParsing (Parser g s) where
   satisfyCharInput predicate = Parser p
      where p rest@((s, _):t) =
               case Textual.characterPrefix s
               of Just first | predicate first -> ResultList [ResultsOfLength 1 t (Factorial.primePrefix s:|[])] mempty
                  _ -> ResultList mempty (expected (Down $ length rest) "satisfyCharInput")
            p [] = ResultList mempty (expected 0 "satisfyCharInput")
   scanChars s0 f = Parser (p s0)
      where p s rest@((i, _) : _) = ResultList [ResultsOfLength l (drop l rest) (prefix:|[])] mempty
               where (prefix, _, _) = Textual.spanMaybe_' s f i
                     l = Factorial.length prefix
            p _ [] = ResultList [ResultsOfLength 0 [] (mempty:|[])] mempty
   takeCharsWhile predicate = Parser p
      where p rest@((s, _) : _)
               | x <- Textual.takeWhile_ False predicate s, l <- Factorial.length x =
                    ResultList [ResultsOfLength l (drop l rest) (x:|[])] mempty
            p [] = ResultList [ResultsOfLength 0 [] (mempty:|[])] mempty
   takeCharsWhile1 predicate = Parser p
      where p rest@((s, _) : _)
               | x <- Textual.takeWhile_ False predicate s, l <- Factorial.length x, l > 0 =
                    ResultList [ResultsOfLength l (drop l rest) (x:|[])] mempty
            p rest = ResultList mempty (expected (Down $ length rest) "takeCharsWhile1")
   notSatisfyChar predicate = Parser p
      where p rest@((s, _):_)
               | Just first <- Textual.characterPrefix s, 
                 predicate first = ResultList mempty (expected (Down $ length rest) "notSatisfyChar")
            p rest = ResultList [ResultsOfLength 0 rest (():|[])] mempty

instance (LeftReductive s, FactorialMonoid s, Ord s) => ConsumedInputParsing (Parser g s) where
   match (Parser p) = Parser q
      where q [] = addConsumed mempty (p [])
            q rest@((s, _) : _) = addConsumed s (p rest)
            addConsumed input (ResultList rl failure) = ResultList (add1 <$> rl) failure
               where add1 (ResultsOfLength l t rs) = ResultsOfLength l t ((,) (Factorial.take l input) <$> rs)

instance (MonoidNull s, Ord s) => Parsing (Parser g s) where
   try (Parser p) = Parser q
      where q rest = rewindFailure (p rest)
               where rewindFailure (ResultList rl _) = ResultList rl (emptyFailure $ fromEnd $ length rest)
   Parser p <?> msg  = Parser q
      where q rest = replaceFailure (p rest)
               where replaceFailure (ResultList [] f) = ResultList [] (replaceExpected (fromEnd $ length rest) msg f)
                     replaceFailure rl = rl
   notFollowedBy (Parser p) = Parser (\input-> rewind input (p input))
      where rewind t (ResultList [] _) = ResultList [ResultsOfLength 0 t (():|[])] mempty
            rewind t ResultList{} = ResultList mempty (expected (Down $ length t) "notFollowedBy")
   skipMany p = go
      where go = pure () <|> try p *> go
   unexpected msg = Parser (\t-> ResultList mempty $ erroneous (Down $ length t) msg)
   eof = Parser f
      where f rest@((s, _):_)
               | null s = ResultList [ResultsOfLength 0 rest (():|[])] mempty
               | otherwise = ResultList mempty (expected (Down $ length rest) "end of input")
            f [] = ResultList [ResultsOfLength 0 [] (():|[])] mempty

instance (MonoidNull s, Ord s) => DeterministicParsing (Parser g s) where
   Parser p <<|> Parser q = Parser r where
      r rest = case p rest
               of rl@(ResultList [] _failure) -> rl <> q rest
                  rl -> rl
   takeSome p = (:) <$> p <*> takeMany p
   takeMany (Parser p) = Parser (q 0 id) where
      q !len acc rest = case p rest
                        of ResultList [] _failure -> ResultList [ResultsOfLength len rest (acc [] :| [])] mempty
                           ResultList rl _ -> foldMap continue rl
         where continue (ResultsOfLength len' rest' results) = foldMap (\r-> q (len + len') (acc . (r:)) rest') results
   skipAll (Parser p) = Parser (q 0) where
      q !len rest = case p rest
                    of ResultList [] _failure -> ResultList [ResultsOfLength len rest (():|[])] mempty
                       ResultList rl _failure -> foldMap continue rl
         where continue (ResultsOfLength len' rest' _) = q (len + len') rest'

instance (MonoidNull s, Ord s) => LookAheadParsing (Parser g s) where
   lookAhead (Parser p) = Parser (\input-> rewind input (p input))
      where rewind _ rl@(ResultList [] _) = rl
            rewind t (ResultList rl failure) = ResultList [ResultsOfLength 0 t $ foldr1 (<>) (results <$> rl)] failure
            results (ResultsOfLength _ _ r) = r

instance (Ord s, Show s, TextualMonoid s) => CharParsing (Parser g s) where
   satisfy predicate = Parser p
      where p rest@((s, _):t) =
               case Textual.characterPrefix s
               of Just first | predicate first -> ResultList [ResultsOfLength 1 t (first:|[])] mempty
                  _ -> ResultList mempty (expected (Down $ length rest) "Char.satisfy")
            p [] = ResultList mempty (expected 0 "Char.satisfy")
   string s = Textual.toString (error "unexpected non-character") <$> string (fromString s)
   text t = (fromString . Textual.toString (error "unexpected non-character")) <$> string (Textual.fromText t)

instance Ord s => AmbiguousParsing (Parser g s) where
   ambiguous (Parser p) = Parser q
      where q rest | ResultList rs failure <- p rest = ResultList (groupByLength <$> rs) failure
            groupByLength (ResultsOfLength l rest rs) = ResultsOfLength l rest (Ambiguous rs :| [])

instance Ord s => CommittedParsing (Parser g s) where
   type CommittedResults (Parser g s) = ParseResults s
   commit (Parser p) = Parser q
      where q rest = case p rest
                     of ResultList [] failure -> ResultList [ResultsOfLength 0 rest (Left failure:|[])] mempty
                        ResultList rl failure -> ResultList (fmap Right <$> rl) failure
   admit (Parser p) = Parser q
      where q rest = case p rest
                     of ResultList [] failure -> ResultList [] failure
                        ResultList rl failure -> foldMap expose rl <> ResultList [] failure
            expose (ResultsOfLength len t rs) = case nonEmpty successes of
               Nothing -> ResultList [] (mconcat failures)
               Just successes' -> ResultList [ResultsOfLength len t successes'] (mconcat failures)
               where (failures, successes) = partitionEithers (toList rs)
        
-- | Turns a context-free parser into a backtracking PEG parser that consumes the longest possible prefix of the list
-- of input tails, opposite of 'peg'
longest :: Parser g s a -> Backtrack.Parser g [(s, g (ResultList g s))] a
longest p = Backtrack.Parser q where
   q rest = case applyParser p rest
            of ResultList [] (ParseFailure pos (FailureDescription expected inputs) errors)
                  -> Backtrack.NoParse (ParseFailure pos (FailureDescription expected $ map wrap inputs) errors)
               ResultList rs _ -> parsed (last rs)
   parsed (ResultsOfLength l s (r:|_)) = Backtrack.Parsed l r s
   wrap s = [(s, error "longest")]

-- | Turns a backtracking PEG parser of the list of input tails into a context-free parser, opposite of 'longest'
peg :: Ord s => Backtrack.Parser g [(s, g (ResultList g s))] a -> Parser g s a
peg p = Parser q where
   q rest = case Backtrack.applyParser p rest
            of Backtrack.Parsed l result suffix -> ResultList [ResultsOfLength l suffix (result:|[])] mempty
               Backtrack.NoParse (ParseFailure pos (FailureDescription expected inputs) errors)
                  -> ResultList mempty (ParseFailure pos (FailureDescription expected (fst . head <$> inputs)) errors)

-- | Turns a backtracking PEG parser into a context-free parser
terminalPEG :: Monoid s => Ord s => Backtrack.Parser g s a -> Parser g s a
terminalPEG p = Parser q where
   q [] = case Backtrack.applyParser p mempty
            of Backtrack.Parsed l result _ -> ResultList [ResultsOfLength l [] (result:|[])] mempty
               Backtrack.NoParse failure -> ResultList mempty failure
   q rest@((s, _):_) = case Backtrack.applyParser p s
                       of Backtrack.Parsed l result _ -> 
                             ResultList [ResultsOfLength l (drop l rest) (result:|[])] mempty
                          Backtrack.NoParse failure -> ResultList mempty failure