{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE NoImplicitPrelude #-}

module Data.Morpheus.Server.Deriving.Decode
  ( decodeArguments,
    Decode (..),
    DecodeConstraint,
  )
where

import Control.Applicative (pure, (<*>))
import Control.Monad ((>>=))
import Data.Functor (Functor (..), (<$>))
import Data.List (elem)
import Data.List.NonEmpty (NonEmpty)
import qualified Data.List.NonEmpty as NonEmpty
import Data.Maybe (Maybe (..))
import Data.Morpheus.Internal.Utils
  ( elems,
  )
import Data.Morpheus.Kind
  ( ENUM,
    GQL_KIND,
    INPUT,
    OUTPUT,
    SCALAR,
  )
import Data.Morpheus.Server.Deriving.Utils
  ( conNameProxy,
    datatypeNameProxy,
    selNameProxy,
  )
import Data.Morpheus.Server.Internal.TH.Decode (decodeFieldWith, withInputObject, withInputUnion, withList, withMaybe, withRefinedList, withScalar)
import Data.Morpheus.Server.Types.GQLType
  ( GQLType
      ( KIND,
        typeOptions,
        __type
      ),
    GQLTypeOptions (..),
    TypeData (..),
  )
import Data.Morpheus.Types.GQLScalar
  ( GQLScalar (..),
  )
import Data.Morpheus.Types.Internal.AST
  ( Argument (..),
    Arguments,
    InternalError,
    ObjectEntry (..),
    TypeName (..),
    VALID,
    ValidObject,
    ValidValue,
    Value (..),
    msg,
  )
import Data.Morpheus.Types.Internal.Resolving
  ( Failure (..),
    ResolverState,
  )
import Data.Proxy (Proxy (..))
import Data.Semigroup (Semigroup (..))
import Data.Sequence (Seq)
import qualified Data.Sequence as Seq
import Data.Set (Set)
import qualified Data.Set as Set
import Data.String (IsString (fromString))
import Data.Vector (Vector)
import qualified Data.Vector as Vector
import GHC.Generics
import Prelude (Either (Left, Right), Eq (..), Foldable (length), Ord, maybe, otherwise, show, ($), (-), (.))

type DecodeConstraint a =
  ( Generic a,
    GQLType a,
    DecodeRep (Rep a)
  )

-- GENERIC
decodeArguments :: DecodeConstraint a => Arguments VALID -> ResolverState a
decodeArguments = decodeType . Object . fmap toEntry
  where
    toEntry Argument {..} = ObjectEntry argumentName argumentValue

-- | Decode GraphQL query arguments and input values
class Decode a where
  decode :: ValidValue -> ResolverState a

instance {-# OVERLAPPABLE #-} DecodeKind (KIND a) a => Decode a where
  decode = decodeKind (Proxy @(KIND a))

instance Decode a => Decode (Maybe a) where
  decode = withMaybe decode

instance Decode a => Decode [a] where
  decode = withList decode

instance Decode a => Decode (NonEmpty a) where
  decode = withRefinedList (maybe (Left "Expected a NonEmpty list") Right . NonEmpty.nonEmpty) decode

-- | Should this instance dedupe silently or fail on dupes ?
instance (Ord a, Decode a) => Decode (Set a) where
  decode val = do
    listVal <- withList (decode @a) val
    let setVal = Set.fromList listVal
    let setLength = length setVal
    let listLength = length setVal
    if listLength == setLength
      then pure setVal
      else failure (fromString ("Expected a List without duplicates, found " <> show (setLength - listLength) <> " duplicates") :: InternalError)

instance (Decode a) => Decode (Seq a) where
  decode = fmap Seq.fromList . withList decode

instance (Decode a) => Decode (Vector a) where
  decode = fmap Vector.fromList . withList decode

-- | Decode GraphQL type with Specific Kind
class DecodeKind (kind :: GQL_KIND) a where
  decodeKind :: Proxy kind -> ValidValue -> ResolverState a

-- SCALAR
instance (GQLScalar a, GQLType a) => DecodeKind SCALAR a where
  decodeKind _ = withScalar (gqlTypeName $ __type (Proxy @a)) parseValue

-- ENUM
instance DecodeConstraint a => DecodeKind ENUM a where
  decodeKind _ = decodeType

-- TODO: remove
instance DecodeConstraint a => DecodeKind OUTPUT a where
  decodeKind _ = decodeType

-- INPUT_OBJECT and  INPUT_UNION
instance DecodeConstraint a => DecodeKind INPUT a where
  decodeKind _ = decodeType

decodeType :: forall a. DecodeConstraint a => ValidValue -> ResolverState a
decodeType = fmap to . decodeRep . (typeOptions (Proxy @a),,Cont D_CONS "")

-- data Input  =
--    InputHuman Human  -- direct link: { __typename: Human, Human: {field: ""} }
--   | InputRecord { name :: Text, age :: Int } -- { __typename: InputRecord, InputRecord: {field: ""} }
--   | IndexedType Int Text  -- { __typename: InputRecord, _0:2 , _1:""  }
--   | Zeus                 -- { __typename: Zeus }
--     deriving (Generic, GQLType)

decideUnion ::
  ([TypeName], value -> ResolverState (f1 a)) ->
  ([TypeName], value -> ResolverState (f2 a)) ->
  TypeName ->
  value ->
  ResolverState ((:+:) f1 f2 a)
decideUnion (left, f1) (right, f2) name value
  | name `elem` left =
    L1 <$> f1 value
  | name `elem` right =
    R1 <$> f2 value
  | otherwise =
    failure $
      "Constructor \""
        <> msg name
        <> "\" could not find in Union"

data Tag = D_CONS | D_UNION deriving (Eq, Ord)

data Cont = Cont
  { contKind :: Tag,
    typeName :: TypeName
  }

data Info = Info
  { kind :: Tag,
    tagName :: [TypeName]
  }

instance Semigroup Info where
  Info D_UNION t1 <> Info _ t2 = Info D_UNION (t1 <> t2)
  Info _ t1 <> Info D_UNION t2 = Info D_UNION (t1 <> t2)
  Info D_CONS t1 <> Info D_CONS t2 = Info D_CONS (t1 <> t2)

--
-- GENERICS
--
class DecodeRep f where
  tags :: Proxy f -> (GQLTypeOptions, TypeName) -> Info
  decodeRep :: (GQLTypeOptions, ValidValue, Cont) -> ResolverState (f a)

instance (Datatype d, DecodeRep f) => DecodeRep (M1 D d f) where
  tags _ = tags (Proxy @f)
  decodeRep (ns, x, y) =
    M1
      <$> decodeRep
        (ns, x, y {typeName = datatypeNameProxy (Proxy @d)})

getEnumTag :: ValidObject -> ResolverState TypeName
getEnumTag x = case elems x of
  [ObjectEntry "enum" (Enum value)] -> pure value
  _ -> failure ("bad union enum object" :: InternalError)

instance (DecodeRep a, DecodeRep b) => DecodeRep (a :+: b) where
  tags _ = tags (Proxy @a) <> tags (Proxy @b)
  decodeRep = __decode
    where
      __decode (opt, Object obj, cont) = withInputUnion handleUnion obj
        where
          handleUnion name unions object
            | name == typeName cont <> "EnumObject" =
              getEnumTag object >>= __decode . (opt,,ctx) . Enum
            | [name] == l1 =
              L1 <$> decodeRep (opt, Object object, ctx)
            | [name] == r1 =
              R1 <$> decodeRep (opt, Object object, ctx)
            | otherwise =
              decideUnion (l1, decodeRep) (r1, decodeRep) name (opt, Object unions, ctx)
          l1 = tagName l1t
          r1 = tagName r1t
          l1t = tags (Proxy @a) (opt, typeName cont)
          r1t = tags (Proxy @b) (opt, typeName cont)
          ctx = cont {contKind = kind (l1t <> r1t)}
      __decode (opt, Enum name, cxt) =
        decideUnion
          (tagName $ tags (Proxy @a) (opt, typeName cxt), decodeRep)
          (tagName $ tags (Proxy @b) (opt, typeName cxt), decodeRep)
          name
          (opt, Enum name, cxt)
      __decode _ = failure ("lists and scalars are not allowed in Union" :: InternalError)

instance (Constructor c, DecodeFields a) => DecodeRep (M1 C c a) where
  decodeRep = fmap M1 . decodeFields
  tags _ (opt, baseName) = getTag (refType (Proxy @a))
    where
      getTag (Just memberRef)
        | isUnionRef memberRef = Info {kind = D_UNION, tagName = [memberRef]}
        | otherwise = Info {kind = D_CONS, tagName = [consName]}
      getTag Nothing = Info {kind = D_CONS, tagName = [consName]}
      --------
      consName = conNameProxy opt (Proxy @c)
      ----------
      isUnionRef x = baseName <> x == consName

class DecodeFields f where
  refType :: Proxy f -> Maybe TypeName
  decodeFields :: (GQLTypeOptions, ValidValue, Cont) -> ResolverState (f a)

instance (DecodeFields f, DecodeFields g) => DecodeFields (f :*: g) where
  refType _ = Nothing
  decodeFields gql = (:*:) <$> decodeFields gql <*> decodeFields gql

instance (Selector s, GQLType a, Decode a) => DecodeFields (M1 S s (K1 i a)) where
  refType _ = Just $ gqlTypeName $ __type (Proxy @a)
  decodeFields (opt, value, Cont {contKind})
    | contKind == D_UNION = M1 . K1 <$> decode value
    | otherwise = __decode value
    where
      __decode = fmap (M1 . K1) . decodeRec
      fieldName = selNameProxy opt (Proxy @s)
      decodeRec = withInputObject (decodeFieldWith decode fieldName)

instance DecodeFields U1 where
  refType _ = Nothing
  decodeFields _ = pure U1