{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE DeriveGeneric       #-}
{-# LANGUAGE DeriveLift          #-}
{-# LANGUAGE FlexibleInstances   #-}
{-# LANGUAGE OverloadedStrings   #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE DataKinds           #-}
{-# LANGUAGE GADTs               #-}
{-# LANGUAGE TemplateHaskell     #-}

module Data.Morpheus.Types.Internal.AST.Value
  ( Value(..)
  , ScalarValue(..)
  , Object
  , GQLValue(..)
  , replaceValue
  , decodeScientific
  , convertToJSONName
  , convertToHaskellName
  , RawValue
  , ValidValue
  , RawObject
  , ValidObject
  , Variable(..)
  , ResolvedValue
  , ResolvedObject
  , VariableContent(..)
  )
where

import qualified Data.Aeson                    as A
                                                ( FromJSON(..)
                                                , ToJSON(..)
                                                , Value(..)
                                                , object
                                                , pairs
                                                , (.=)
                                                )
import qualified Data.HashMap.Strict           as M
                                                ( toList )
import           Data.Scientific                ( Scientific
                                                , floatingOrInteger
                                                )
import           Data.Semigroup                 ( (<>) )
import           Data.Text                      ( Text
                                                , unpack
                                                )
import qualified Data.Text                     as T
import qualified Data.Vector                   as V
                                                ( toList )
import           GHC.Generics                   ( Generic )
import           Instances.TH.Lift              ( )
import           Language.Haskell.TH.Syntax     ( Lift(..) )

-- MORPHEUS
import           Data.Morpheus.Types.Internal.AST.Base
                                                ( Collection
                                                , Ref(..)
                                                , Name
                                                , RAW
                                                , VALID
                                                , Position
                                                , Stage
                                                , RESOLVED
                                                , TypeRef
                                                )


isReserved :: Name -> Bool
isReserved "case"     = True
isReserved "class"    = True
isReserved "data"     = True
isReserved "default"  = True
isReserved "deriving" = True
isReserved "do"       = True
isReserved "else"     = True
isReserved "foreign"  = True
isReserved "if"       = True
isReserved "import"   = True
isReserved "in"       = True
isReserved "infix"    = True
isReserved "infixl"   = True
isReserved "infixr"   = True
isReserved "instance" = True
isReserved "let"      = True
isReserved "module"   = True
isReserved "newtype"  = True
isReserved "of"       = True
isReserved "then"     = True
isReserved "type"     = True
isReserved "where"    = True
isReserved "_"        = True
isReserved _          = False

{-# INLINE isReserved #-}
convertToJSONName :: Text -> Text
convertToJSONName hsName
  | not (T.null hsName) && isReserved name && (T.last hsName == '\'') = name
  | otherwise = hsName
  where name = T.init hsName

convertToHaskellName :: Text -> Text
convertToHaskellName name | isReserved name = name <> "'"
                          | otherwise       = name

-- | Primitive Values for GQLScalar: 'Int', 'Float', 'String', 'Boolean'.
-- for performance reason type 'Text' represents GraphQl 'String' value
data ScalarValue
  = Int Int
  | Float Float
  | String Text
  | Boolean Bool
  deriving (Show, Generic,Lift)

instance A.ToJSON ScalarValue where
  toJSON (Float   x) = A.toJSON x
  toJSON (Int     x) = A.toJSON x
  toJSON (Boolean x) = A.toJSON x
  toJSON (String  x) = A.toJSON x

instance A.FromJSON ScalarValue where
  parseJSON (A.Bool   v) = pure $ Boolean v
  parseJSON (A.Number v) = pure $ decodeScientific v
  parseJSON (A.String v) = pure $ String v
  parseJSON notScalar    = fail $ "Expected Scalar got :" <> show notScalar

type family VAR (a:: Stage) :: Stage
type instance VAR RAW = RESOLVED
type instance VAR RESOLVED = RESOLVED
type instance VAR VALID = VALID

data VariableContent (stage:: Stage) where
  DefaultValue ::Maybe ResolvedValue -> VariableContent RESOLVED
  ValidVariableValue ::{ validVarContent::ValidValue }-> VariableContent VALID

instance Lift (VariableContent a) where
  lift (DefaultValue       x) = [| DefaultValue x |]
  lift (ValidVariableValue x) = [| ValidVariableValue x |]

deriving instance Show (VariableContent a)

data Variable (stage :: Stage) = Variable
  { variableType         :: TypeRef
  , variablePosition     :: Position
  , variableValue        :: VariableContent (VAR stage)
  } deriving (Show,Lift)

data Value (valid :: Stage) where
  ResolvedVariable::Ref -> Variable VALID -> Value RESOLVED
  VariableValue ::Ref -> Value RAW
  Object  ::Object a -> Value a
  List ::[Value a] -> Value a
  Enum ::Name -> Value a
  Scalar ::ScalarValue -> Value a
  Null ::Value a


type Object a = Collection (Value a)
type ValidObject = Object VALID
type RawObject = Object RAW
type ResolvedObject = Object RESOLVED
type RawValue = Value RAW
type ValidValue = Value VALID
type ResolvedValue = Value RESOLVED

deriving instance Lift (Value a)

instance Show (Value a) where
  show Null       = "null"
  show (Enum   x) = "" <> unpack x
  show (Scalar x) = show x
  show (ResolvedVariable Ref { refName } Variable { variableValue }) =
    "($" <> unpack refName <> ": " <> show variableValue <> ") "
  show (VariableValue Ref { refName }) = "$" <> unpack refName <> " "
  show (Object        keys           ) = "{" <> foldl toEntry "" keys <> "}"
   where
    toEntry :: String -> (Name, Value a) -> String
    toEntry ""  (key, value) = unpack key <> ":" <> show value
    toEntry txt (key, value) = txt <> ", " <> unpack key <> ":" <> show value
  show (List list) = "[" <> foldl toEntry "" list <> "]"
   where
    toEntry :: String -> Value a -> String
    toEntry ""  value = show value
    toEntry txt value = txt <> ", " <> show value

instance A.ToJSON (Value a) where
  toJSON (ResolvedVariable _ Variable { variableValue = ValidVariableValue x })
    = A.toJSON x
  toJSON (VariableValue Ref { refName }) =
    A.String $ "($ref:" <> refName <> ")"
  toJSON Null            = A.Null
  toJSON (Enum   x     ) = A.String x
  toJSON (Scalar x     ) = A.toJSON x
  toJSON (List   x     ) = A.toJSON x
  toJSON (Object fields) = A.object $ map toEntry fields
    where toEntry (name, value) = name A..= A.toJSON value
  -------------------------------------------
  toEncoding (ResolvedVariable _ Variable { variableValue = ValidVariableValue x })
    = A.toEncoding x
  toEncoding (VariableValue Ref { refName }) =
    A.toEncoding $ "($ref:" <> refName <> ")"
  toEncoding Null        = A.toEncoding A.Null
  toEncoding (Enum   x ) = A.toEncoding x
  toEncoding (Scalar x ) = A.toEncoding x
  toEncoding (List   x ) = A.toEncoding x
  toEncoding (Object []) = A.toEncoding $ A.object []
  toEncoding (Object x ) = A.pairs $ foldl1 (<>) $ map encodeField x
    where encodeField (key, value) = convertToJSONName key A..= value

decodeScientific :: Scientific -> ScalarValue
decodeScientific v = case floatingOrInteger v of
  Left  float -> Float float
  Right int   -> Int int

replaceValue :: A.Value -> Value a
replaceValue (A.Bool   v) = gqlBoolean v
replaceValue (A.Number v) = Scalar $ decodeScientific v
replaceValue (A.String v) = gqlString v
replaceValue (A.Object v) = gqlObject $ map replace (M.toList v)
  where
  --replace :: (a, A.Value) -> (a, Value a)
        replace (key, val) = (key, replaceValue val)
replaceValue (A.Array li) = gqlList (map replaceValue (V.toList li))
replaceValue A.Null       = gqlNull

instance A.FromJSON (Value a) where
  parseJSON = pure . replaceValue

-- DEFAULT VALUES
class GQLValue a where
  gqlNull :: a
  gqlScalar :: ScalarValue -> a
  gqlBoolean :: Bool -> a
  gqlString :: Text -> a
  gqlList :: [a] -> a
  gqlObject :: [(Name, a)] -> a

-- build GQL Values for Subscription Resolver
instance GQLValue (Value a) where
  gqlNull    = Null
  gqlScalar  = Scalar
  gqlBoolean = Scalar . Boolean
  gqlString  = Scalar . String
  gqlList    = List
  gqlObject  = Object