{-# LANGUAGE FlexibleInstances     #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE NamedFieldPuns        #-}
{-# LANGUAGE OverloadedStrings     #-}
{-# LANGUAGE TypeOperators         #-}
{-# LANGUAGE ScopedTypeVariables   #-}

module Data.Morpheus.Parsing.JSONSchema.Parse
  ( decodeIntrospection
  )
where

import           Data.Aeson
import           Data.ByteString.Lazy           ( ByteString )
import           Data.Morpheus.Error.Internal   ( internalError )
import           Data.Morpheus.Parsing.JSONSchema.Types
                                                ( EnumValue(..)
                                                , Field(..)
                                                , InputValue(..)
                                                , Introspection(..)
                                                , Schema(..)
                                                , Type(..)
                                                )
import           Data.Morpheus.Schema.TypeKind  ( TypeKind(..) )
import qualified Data.Morpheus.Types.Internal.AST as AST
                                                ( Schema)
import           Data.Morpheus.Types.Internal.AST
                                                ( FieldDefinition
                                                , TypeDefinition(..)
                                                , TypeContent(..)
                                                , DataTypeWrapper(..)
                                                , TypeWrapper
                                                , createArgument
                                                , createDataTypeLib
                                                , createEnumType
                                                , createField
                                                , createScalarType
                                                , createType
                                                , createUnionType
                                                , toHSWrappers
                                                , ArgumentsDefinition(..)
                                                )
import           Data.Morpheus.Types.Internal.Operation
                                                ( Listable(..))
import           Data.Morpheus.Types.Internal.Resolving
                                                ( Eventless )
import           Data.Morpheus.Types.IO         ( JSONResponse(..) )
import           Data.Semigroup                 ( (<>) )
import           Data.Text                      ( Text
                                                , pack
                                                )

decodeIntrospection :: ByteString -> Eventless AST.Schema
decodeIntrospection jsonDoc = case jsonSchema of
  Left errors -> internalError $ pack errors
  Right JSONResponse { responseData = Just Introspection { __schema = Schema { types } } }
    -> traverse parse types >>= createDataTypeLib . concat
  Right res -> internalError (pack $ show res)
 where
  jsonSchema :: Either String (JSONResponse Introspection)
  jsonSchema = eitherDecode jsonDoc

class ParseJSONSchema a b where
  parse :: a -> Eventless b

instance ParseJSONSchema Type [TypeDefinition] where
  parse Type { name = Just typeName, kind = SCALAR } =
    pure [createScalarType typeName]
  parse Type { name = Just typeName, kind = ENUM, enumValues = Just enums } =
    pure [createEnumType typeName (map enumName enums)]
  parse Type { name = Just typeName, kind = UNION, possibleTypes = Just unions }
    = case traverse name unions of
      Nothing  -> internalError "ERROR: GQL ERROR"
      Just uni -> pure [createUnionType typeName uni]
  parse Type { name = Just typeName, kind = INPUT_OBJECT, inputFields = Just iFields }
    = do
      (fields :: [FieldDefinition]) <- traverse parse iFields
      fs <- fromList fields
      pure [createType typeName $ DataInputObject fs]
  parse Type { name = Just typeName, kind = OBJECT, fields = Just oFields } =
    do
      (fields :: [FieldDefinition]) <- traverse parse oFields
      fs <- fromList fields
      pure [createType typeName $ DataObject [] fs] 
  parse _ = pure []

instance ParseJSONSchema Field FieldDefinition where
  parse Field { fieldName, fieldArgs, fieldType } = do
    fType <- fieldTypeFromJSON fieldType
    args  <- traverse genArg fieldArgs  >>= fromList 
    pure $ createField (ArgumentsDefinition Nothing args) fieldName fType
   where
    genArg InputValue { inputName = argName, inputType = argType } =
      createArgument argName <$> fieldTypeFromJSON argType

instance ParseJSONSchema InputValue FieldDefinition where
  parse InputValue { inputName, inputType } = createField NoArguments inputName <$> fieldTypeFromJSON inputType

fieldTypeFromJSON :: Type -> Eventless ([TypeWrapper], Text)
fieldTypeFromJSON = fmap toHs . fieldTypeRec []
 where
  toHs (w, t) = (toHSWrappers w, t)
  fieldTypeRec
    :: [DataTypeWrapper] -> Type -> Eventless ([DataTypeWrapper], Text)
  fieldTypeRec acc Type { kind = LIST, ofType = Just ofType } =
    fieldTypeRec (ListType : acc) ofType
  fieldTypeRec acc Type { kind = NON_NULL, ofType = Just ofType } =
    fieldTypeRec (NonNullType : acc) ofType
  fieldTypeRec acc Type { name = Just name } = pure (acc, name)
  fieldTypeRec _ x = internalError $ "Unsuported Field" <> pack (show x)