module Data.Noun.Poet where

import ClassyPrelude hiding (fromList)
import Control.Lens

import Control.Applicative
import Control.Monad
import Data.Noun
import Data.Noun.Atom
import Data.Noun.Pill
import Data.Void
import Data.Word
import GHC.Natural

import Data.List      (intercalate)
import Data.Typeable  (Typeable)

import qualified Control.Monad.Fail as Fail


-- Types For Hoon Constructs ---------------------------------------------------

{-|
    `Nullable a <-> ?@(~ a)`

    This is distinct from `unit`, since there is no tag on the non-atom
    case, therefore `a` must always be cell type.
-}
data Nullable a = Nil | NotNil a
  deriving (Eq, Ord, Show)

newtype Cord = Cord ByteString
  deriving newtype (Eq, Ord, Show)


-- IResult ---------------------------------------------------------------------

data IResult a = IError NounPath String | ISuccess a
  deriving (Eq, Show, Typeable, Functor, Foldable, Traversable)

instance Applicative IResult where
    pure  = ISuccess
    (<*>) = ap

instance Fail.MonadFail IResult where
    fail err = IError [] err

instance Monad IResult where
    return = pure
    fail   = Fail.fail
    ISuccess a      >>= k = k a
    IError path err >>= _ = IError path err

instance MonadPlus IResult where
    mzero = fail "mzero"
    mplus a@(ISuccess _) _ = a
    mplus _ b              = b

instance Alternative IResult where
    empty = mzero
    (<|>) = mplus

instance Semigroup (IResult a) where
    (<>) = mplus

instance Monoid (IResult a) where
    mempty  = fail "mempty"
    mappend = (<>)


-- Result ----------------------------------------------------------------------

data Result a = Error String | Success a
  deriving (Eq, Show, Typeable, Functor, Foldable, Traversable)

instance Applicative Result where
    pure  = Success
    (<*>) = ap

instance Fail.MonadFail Result where
    fail err = Error err

instance Monad Result where
    return = pure
    fail   = Fail.fail

    Success a >>= k = k a
    Error err >>= _ = Error err

instance MonadPlus Result where
    mzero = fail "mzero"
    mplus a@(Success _) _ = a
    mplus _ b             = b

instance Alternative Result where
    empty = mzero
    (<|>) = mplus

instance Semigroup (Result a) where
    (<>) = mplus
    {-# INLINE (<>) #-}

instance Monoid (Result a) where
    mempty  = fail "mempty"
    mappend = (<>)


-- "Parser" --------------------------------------------------------------------

type Failure f r   = NounPath -> String -> f r
type Success a f r = a -> f r

newtype Parser a = Parser {
  runParser :: forall f r.  NounPath -> Failure f r -> Success a f r -> f r
}

instance Monad Parser where
    m >>= g = Parser $ \path kf ks -> let ks' a = runParser (g a) path kf ks
                                       in runParser m path kf ks'
    return = pure
    fail = Fail.fail

instance Fail.MonadFail Parser where
    fail msg = Parser $ \path kf _ks -> kf (reverse path) msg

instance Functor Parser where
    fmap f m = Parser $ \path kf ks -> let ks' a = ks (f a)
                                        in runParser m path kf ks'

apP :: Parser (a -> b) -> Parser a -> Parser b
apP d e = do
  b <- d
  b <$> e

instance Applicative Parser where
    pure a = Parser $ \_path _kf ks -> ks a
    (<*>) = apP

instance Alternative Parser where
    empty = fail "empty"
    (<|>) = mplus

instance MonadPlus Parser where
    mzero = fail "mzero"
    mplus a b = Parser $ \path kf ks -> let kf' _ _ = runParser b path kf ks
                                         in runParser a path kf' ks

instance Semigroup (Parser a) where
    (<>) = mplus

instance Monoid (Parser a) where
    mempty  = fail "mempty"
    mappend = (<>)


-- Conversion ------------------------------------------------------------------

class FromNoun a where
  parseNoun :: Noun -> Parser a

class ToNoun a where
  toNoun :: a -> Noun

fromNoun :: FromNoun a => Noun -> Maybe a
fromNoun n = runParser (parseNoun n) [] onFail onSuccess
  where
    onFail p m  = Nothing
    onSuccess x = Just x

_Poet :: (ToNoun a, FromNoun a) => Prism' Noun a
_Poet = prism' toNoun fromNoun


-- Trivial Conversion ----------------------------------------------------------

instance ToNoun Void where
  toNoun = absurd

instance FromNoun Void where
  parseNoun = fail "Can't produce void"

instance ToNoun Noun where
  toNoun = id

instance FromNoun Noun where
  parseNoun = pure


-- Loobean Conversion ----------------------------------------------------------

instance ToNoun Bool where
  toNoun True  = Atom 0
  toNoun False = Atom 1

instance FromNoun Bool where
  parseNoun (Atom 0)   = pure True
  parseNoun (Atom 1)   = pure False
  parseNoun (Cell _ _) = fail "expecting a bool, but got a cell"
  parseNoun (Atom a)   = fail ("expecting a bool, but got " <> show a)


-- Atom Conversion -------------------------------------------------------------

instance ToNoun Atom where
  toNoun = Atom

instance FromNoun Atom where
  parseNoun (Cell _ _) = fail "Expecting an atom, but got a cell"
  parseNoun (Atom a)   = pure a


-- Natural Conversion-----------------------------------------------------------

instance ToNoun Natural   where toNoun    = toNoun . MkAtom
instance FromNoun Natural where parseNoun = fmap unAtom . parseNoun


-- Word Conversion -------------------------------------------------------------

atomToWord :: forall a. (Bounded a, Integral a) => Atom -> Parser a
atomToWord atom = do
  if atom > fromIntegral (maxBound :: a)
  then fail "Atom doesn't fit in fixed-size word"
  else pure (fromIntegral atom)

wordToNoun :: Integral a => a -> Noun
wordToNoun = Atom . fromIntegral

nounToWord :: forall a. (Bounded a, Integral a) => Noun -> Parser a
nounToWord = parseNoun >=> atomToWord

instance ToNoun Word    where toNoun = wordToNoun
instance ToNoun Word8   where toNoun = wordToNoun
instance ToNoun Word16  where toNoun = wordToNoun
instance ToNoun Word32  where toNoun = wordToNoun
instance ToNoun Word64  where toNoun = wordToNoun

instance FromNoun Word    where parseNoun = nounToWord
instance FromNoun Word8   where parseNoun = nounToWord
instance FromNoun Word16  where parseNoun = nounToWord
instance FromNoun Word32  where parseNoun = nounToWord
instance FromNoun Word64  where parseNoun = nounToWord


-- Nullable Conversion ---------------------------------------------------------

-- TODO Consider enforcing that `a` must be a cell.
instance ToNoun a => ToNoun (Nullable a) where
  toNoun Nil        = Atom 0
  toNoun (NotNil x) = toNoun x

instance FromNoun a => FromNoun (Nullable a) where
  parseNoun (Atom 0) = pure Nil
  parseNoun (Atom n) = fail ("Expected ?@(~ ^), but got " <> show n)
  parseNoun n        = NotNil <$> parseNoun n


-- Maybe is `unit` -------------------------------------------------------------

-- TODO Consider enforcing that `a` must be a cell.
instance ToNoun a => ToNoun (Maybe a) where
  toNoun Nothing  = Atom 0
  toNoun (Just x) = Cell (Atom 0) (toNoun x)

instance FromNoun a => FromNoun (Maybe a) where
  parseNoun = \case
      Atom          0   -> pure Nothing
      Atom          n   -> unexpected ("atom " <> show n)
      Cell (Atom 0) t   -> Just <$> parseNoun t
      Cell n        _   -> unexpected ("cell with head-atom " <> show n)
    where
      unexpected s = fail ("Expected unit value, but got " <> s)


-- List Conversion -------------------------------------------------------------

instance ToNoun a => ToNoun [a] where
  toNoun xs = fromList (toNoun <$> xs)

instance FromNoun a => FromNoun [a] where
  parseNoun (Atom 0)   = pure []
  parseNoun (Atom _)   = fail "list terminated with non-null atom"
  parseNoun (Cell l r) = (:) <$> parseNoun l <*> parseNoun r


-- Cord Conversion -------------------------------------------------------------

instance ToNoun Cord where
  toNoun (Cord bs) = Atom (bs ^. from (pill . pillBS))

instance FromNoun Cord where
  parseNoun n = do
    atom <- parseNoun n
    pure $ Cord (atom ^. pill . pillBS)


-- Pair Conversion -------------------------------------------------------------

instance (ToNoun a, ToNoun b) => ToNoun (a, b) where
  toNoun (x, y) = Cell (toNoun x) (toNoun y)

instance (FromNoun a, FromNoun b) => FromNoun (a, b) where
  parseNoun (Atom n)   = fail ("expected a cell, but got an atom: " <> show n)
  parseNoun (Cell l r) = (,) <$> parseNoun l <*> parseNoun r


-- Trel Conversion -------------------------------------------------------------

instance (ToNoun a, ToNoun b, ToNoun c) => ToNoun (a, b, c) where
  toNoun (x, y, z) = toNoun (x, (y, z))

instance (FromNoun a, FromNoun b, FromNoun c) => FromNoun (a, b, c) where
  parseNoun n = do
    (x, t) <- parseNoun n
    (y, z) <- parseNoun t
    pure (x, y, z)


-- Quad Conversion -------------------------------------------------------------

instance (ToNoun a, ToNoun b, ToNoun c, ToNoun d) => ToNoun (a, b, c, d) where
  toNoun (p, q, r, s) = toNoun (p, (q, r, s))

instance (FromNoun a, FromNoun b, FromNoun c, FromNoun d)
      => FromNoun (a, b, c, d)
      where
  parseNoun n = do
    (p, tail) <- parseNoun n
    (q, r, s) <- parseNoun tail
    pure (p, q, r, s)


-- Pent Conversion ------------------------------------------------------------

instance (ToNoun a, ToNoun b, ToNoun c, ToNoun d, ToNoun e)
      => ToNoun (a, b, c, d, e) where
  toNoun (p, q, r, s, t) = toNoun (p, (q, r, s, t))

instance (FromNoun a, FromNoun b, FromNoun c, FromNoun d, FromNoun e)
      => FromNoun (a, b, c, d, e)
      where
  parseNoun n = do
    (p, tail)    <- parseNoun n
    (q, r, s, t) <- parseNoun tail
    pure (p, q, r, s, t)


-- Sext Conversion ------------------------------------------------------------

instance (ToNoun a, ToNoun b, ToNoun c, ToNoun d, ToNoun e, ToNoun f)
      => ToNoun (a, b, c, d, e, f) where
  toNoun (p, q, r, s, t, u) = toNoun (p, (q, r, s, t, u))

instance (FromNoun a, FromNoun b, FromNoun c, FromNoun d, FromNoun e,FromNoun f)
      => FromNoun (a, b, c, d, e, f)
      where
  parseNoun n = do
    (p, tail)       <- parseNoun n
    (q, r, s, t, u) <- parseNoun tail
    pure (p, q, r, s, t, u)