{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE OverloadedStrings #-}

-- |
-- Module      : Hasura.Server.OpenAPI
-- Description : Builds an OpenAPI specification for the REST endpoints from a SchemaCache via the `declareOpenApiSpec` function.
--
-- The implementation currently iterates over the endpoints building up `EndpointData` for each then exposes this as an OpenAPI Schema.
--
-- Most functions are in the `Declare` monad so that they can add new component definitions on the fly that can be referenced.
--   This is especially useful for the params and request body documentation.
--
-- The response body recurses over the SelectionSet Fields associated with an endpoint and looks up types by name in
--   a `RemoteSchemaIntrospection` result generated from the `SchemaCache`.
--
-- Response bodies are mostly delcared inline, since the associated query will likely be unique and determine the fields
--   contained in the response.
module Hasura.Server.OpenAPI (serveJSON) where

import Control.Lens
import Data.Aeson qualified as J
import Data.Aeson.Ordered qualified as JO
import Data.HashMap.Strict qualified as Map
import Data.HashMap.Strict.InsOrd qualified as OMap
import Data.List.NonEmpty qualified as NE
import Data.OpenApi
import Data.OpenApi.Declare
import Data.Set qualified as Set
import Data.Text qualified as T
import Data.Text.Extended (commaSeparated)
import Data.Text.NonEmpty
import Hasura.GraphQL.Analyse (Analysis (Analysis, _aFields, _aVars), FieldAnalysis (FieldAnalysis, _fFields), FieldDef (FieldInfo, FieldList), analyzeGraphqlQuery)
import Hasura.GraphQL.Context
import Hasura.GraphQL.Namespace (mkUnNamespacedRootFieldAlias)
import Hasura.GraphQL.Parser.Schema (Variable)
import Hasura.GraphQL.RemoteServer (introspectionQuery, parseIntrospectionResult)
import Hasura.GraphQL.Transport.HTTP.Protocol
import Hasura.Prelude hiding (get, put)
import Hasura.RQL.IR.Root
import Hasura.RQL.Types.Endpoint
import Hasura.RQL.Types.QueryCollection
import Hasura.RQL.Types.RemoteSchema
import Hasura.RQL.Types.SchemaCache
import Hasura.Session (adminRoleName)
import Language.GraphQL.Draft.Syntax qualified as G
import Network.HTTP.Media.MediaType ((//))

data EndpointData = EndpointData
  { _edUrl :: String,
    _edMethod :: [Text],
    _edVarList :: [Referenced Param],
    _edProperties :: InsOrdHashMap Text (Referenced Schema),
    _edResponse :: Maybe Response,
    _edDescription :: Text, -- contains API comments and graphql query
    _edName :: Text
  }
  deriving (Show)

-- * Response Body Related Functions.

{-

Example stepthrough initiated by call to getSelectionSchema:

  * Endpoint insert_foo
  * getExecutableDefinitions -> List (Normally 1 entry)
  * ExecutableDefinitionOperation -> OperationDefinitionTyped -> TypedOperationDefinition (_todType = OperationTypeMutation)
  * _todSelectionSet ->
    [SelectionField
      (Field{ _fName = Name{unName = "insert_foo"},
            _fSelectionSet
              = [SelectionField
                  (Field{ _fName = Name{unName = "returning"},
                        _fSelectionSet
                          = [..., SelectionField
                              (Field{ _fName = Name{unName = "id"},
                                    _fSelectionSet = []}),
  * Lookup introspection schema, Under mutation_root (inferred from operationtype = OperationTypeMutation)
    RemoteSchemaIntrospection
    (fromList
        [..., (Name{unName = "mutation_root"},
          TypeDefinitionObject
            (ObjectTypeDefinition{_otdDescription =
                                    Just (Description{unDescription = "mutation root"}),
                                  _otdName = Name{unName = "mutation_root"},
                                  _otdImplementsInterfaces = [], _otdDirectives = [],
                                  _otdFieldsDefinition =
                                    [..., FieldDefinition{_fldDescription = Just (Description{unDescription = "insert data into the table: \"foo\""}),
                                                    _fldName = Name{unName = "insert_foo"},
                                                    _fldType = TypeNamed (Nullability{unNullability = True}) (Name{unName = "foo_mutation_response"}),
  * Find that type for insert_foo field in mutation_root is named type "foo_mutation_response"
  * Look up "foo_mutation_response" in introspection schema:
        (Name{unName = "foo_mutation_response"},
          TypeDefinitionObject
            (ObjectTypeDefinition{_otdDescription = Just (Description{unDescription = "response of any mutation on the table \"foo\""}),
                                  _otdName = Name{unName = "foo_mutation_response"},
                                  _otdFieldsDefinition =
                                    [..., FieldDefinition{_fldDescription =
                                                      Just
                                                        (Description{unDescription =
                                                                        "data from the rows affected by the mutation"}),
                                                    _fldName = Name{unName = "returning"},
                                                    _fldArgumentsDefinition = [],
                                                    _fldType =
                                                      TypeList (Nullability{unNullability = False})
                                                        (TypeNamed
                                                            (Nullability{unNullability = False})
                                                            (Name{unName = "foo"})),
                                                    _fldDirectives = []}]})),
  * Find first referenced sub-field "returning"
  * It has type (TypeNamed (Name{unName = "foo"})),
  * Look up "foo" in Introspection Schema: ...,
        (Name{unName = "foo"},
          TypeDefinitionObject
            (ObjectTypeDefinition{_otdDescription = Just (Description{unDescription = "columns and relationships of \"foo\""}),
                                  _otdName = Name{unName = "foo"}, _otdImplementsInterfaces = [],
                                  _otdFieldsDefinition =
                                    [ ..., FieldDefinition{_fldDescription = Nothing,
                                                    _fldName = Name{unName = "id"},
                                                    _fldType = TypeNamed (Nullability{unNullability = False}) (Name{unName = "uuid"}),
  * Lookup first sub-sub field by SelectionSet field name "id"
  * See that it has type: TypeNamed (Name{unName = "uuid"})
  * See that there are no sub-sub-sub fields
  * declare type uuid by looking up its definition
        (Name{unName = "uuid"},
        TypeDefinitionScalar
          (ScalarTypeDefinition{_stdDescription = Nothing,
                                _stdName = Name{unName = "uuid"}, _stdDirectives = []})),
  * reference type name from components in output

  ... Proceed with other sub-fields and fields

-}

-- FIXME: There should only be one definition associated. Find a way to signal an error here otherwise.
mdDefinitions :: EndpointMetadata GQLQueryWithText -> [G.ExecutableDefinition G.Name]
mdDefinitions = G.getExecutableDefinitions . unGQLQuery . getGQLQuery . _edQuery . _ceDefinition

mkResponse :: [Text] -> String -> Maybe RemoteSchemaIntrospection -> Analysis G.Name -> Declare (Definitions Schema) (Maybe Response)
mkResponse _ _ Nothing _ = pure Nothing
mkResponse epMethods epUrl (Just rs) Analysis {..} = do
  fs <- getSelectionSchema rs (OMap.toList _aFields)
  pure $
    Just $
      mempty
        & content .~ OMap.singleton ("application" // "json") (mempty & schema ?~ Inline fs)
        & description .~ "Responses for " <> commaSeparated epMethods <> " " <> T.pack epUrl

getSelectionSchema :: RemoteSchemaIntrospection -> [(G.Name, (FieldDef, Maybe (FieldAnalysis var)))] -> Declare (Definitions Schema) Schema
getSelectionSchema rs fields = do
  ps <- traverse (pure . G.unName . fst &&&& (\(fN, (td, fA)) -> getDefinitionSchema rs fN td fA {- (\(fN,(td,fA)) -> pure $ (G.unName fN,) $ getDefinitionSchema rs td fA) -})) fields
  pure $ mempty & properties .~ OMap.fromList (map (second Inline) ps)

-- | A helper function to set the pattern field in Schema
--   Why not lens `pattern`? hlint doesn't like the name `pattern`
--   https://github.com/ndmitchell/hlint/issues/607
setPattern :: Maybe Pattern -> Schema -> Schema
setPattern p s = s {_schemaPattern = p}

getDefinitionSchema ::
  RemoteSchemaIntrospection ->
  G.Name ->
  FieldDef ->
  Maybe (FieldAnalysis var) ->
  Declare (Definitions Schema) Schema
getDefinitionSchema rs tn fd fA =
  typeToSchemaM
    fd
    ( \case
        (G.TypeDefinitionInterface _) -> pure $ mempty & description ?~ "Unsupported field type TypeDefinitionInterface: " <> G.unName tn
        (G.TypeDefinitionUnion _) -> pure $ mempty & description ?~ "Unsupported field type TypeDefinitionUnion: " <> G.unName tn
        (G.TypeDefinitionEnum _) -> pure $ mempty & description ?~ "Unsupported field type TypeDefinitionEnum: " <> G.unName tn
        (G.TypeDefinitionInputObject _) -> pure $ mempty & description ?~ "Unsupported field type TypeDefinitionInputObject: " <> G.unName tn
        (G.TypeDefinitionObject _) ->
          case fA of
            Nothing -> pure $ mempty & description ?~ "Field analysis not found"
            Just FieldAnalysis {..} -> do
              ps <- traverse (pure . G.unName . fst &&&& (\(fN, (td', fA')) -> getDefinitionSchema rs fN td' fA')) (OMap.toList _fFields)
              pure $
                mempty
                  & properties .~ OMap.fromList (map (second Inline) ps)
                  & type_ ?~ OpenApiObject
        (G.TypeDefinitionScalar std) -> do
          let (refType, patt) = referenceType True (T.toLower $ G.unName $ G._stdName std)
          pure $
            mempty
              & title ?~ G.unName (G._stdName std)
              & description .~ (G.unDescription <$> G._stdDescription std)
              & type_ .~ refType
              & setPattern patt
    )

typeToSchemaM :: Monad m => FieldDef -> (G.TypeDefinition [G.Name] RemoteSchemaInputValueDefinition -> m Schema) -> m Schema
typeToSchemaM (FieldInfo _nullability tName) k = k tName
typeToSchemaM (FieldList n t) k = do
  t' <- typeToSchemaM t k
  pure $
    mempty
      & nullable ?~ G.unNullability n
      & type_ ?~ OpenApiArray
      & items ?~ OpenApiItemsObject (Inline t') -- TODO: Why do we assume objects here?

infixl 7 &&&&

(&&&&) :: Applicative f => (t -> f a1) -> (t -> f a2) -> t -> f (a1, a2)
f &&&& g = \a -> (,) <$> f a <*> g a

-- * URL / Query Params and Request Body Functions

-- There could be an additional partitioning scheme besides referentiality to support more types in Params
getParams :: Analysis G.Name -> EndpointUrl -> [Referenced Param]
getParams Analysis {..} eURL = varDetails =<< Map.toList _aVars
  where
    pathVars = map T.tail $ concat $ splitPath pure (const []) eURL -- NOTE: URL Variable name ':' prefix is removed for `elem` lookup.
    varDetails (_vdName, (_vdType, _vdDefaultValue)) =
      let vName = G.unName _vdName
          isRequired = not $ G.isNullable _vdType
       in case getType _vdType of
            Left _foo -> [] -- Complex types are not allowed as params
            Right (vdType, patt) ->
              pure $
                Inline $
                  mkParam
                    vName
                    (if isRequired then Just $ "_\"" <> vName <> "\" is required (enter it either in parameters or request body)_" else Nothing)
                    Nothing
                    (if vName `elem` pathVars then ParamPath else ParamQuery)
                    Nothing
                    (gqlToJsonValue <$> _vdDefaultValue)
                    (Just vdType)
                    patt

getType :: G.GType -> Either G.GType (OpenApiType, Maybe Pattern)
getType gt@(G.TypeNamed _ na) = case referenceType True t of
  (Nothing, _) -> Left gt
  (Just typ, patt) -> Right (typ, patt)
  where
    t = T.toLower $ G.unName na
getType t = Left t -- Non scalar types are deferred to reference types for processing using introspection

mkProperties :: Maybe RemoteSchemaIntrospection -> Analysis G.Name -> Declare (Definitions Schema) (InsOrdHashMap Text (Referenced Schema))
mkProperties sd Analysis {..} = OMap.fromList <$> traverse (mkProperty sdMap) ds
  where
    ds = Map.toList _aVars
    sdMap = case sd of
      Nothing -> OMap.empty
      Just (RemoteSchemaIntrospection sd') -> OMap.fromList $ map (first G.unName) $ Map.toList sd'

mkProperty :: InsOrdHashMap Text (G.TypeDefinition [G.Name] RemoteSchemaInputValueDefinition) -> (G.Name, (G.GType, Maybe (G.Value Void))) -> Declare (Definitions Schema) (Text, Referenced Schema)
mkProperty sd (_vdName, (_vdType, _vdDefaultValue)) = do
  d <- case getType _vdType of
    Left t -> handleRefType sd t
    Right (vdType, patt) ->
      pure $
        Inline $
          mempty
            & nullable ?~ G.isNullable _vdType
            & type_ ?~ vdType
            & default_ .~ fmap gqlToJsonValue _vdDefaultValue
            & setPattern patt

  pure (G.unName _vdName, d)

handleRefType :: OMap.InsOrdHashMap Text (G.TypeDefinition a RemoteSchemaInputValueDefinition) -> G.GType -> Declare (Definitions Schema) (Referenced Schema)
handleRefType sd = \case
  G.TypeNamed nullability nameWrapper -> do
    let n = G.unName nameWrapper
    declareReference nullability n sd
    pure $ Ref $ Reference n
  G.TypeList nullability subType -> do
    st <- handleRefType sd subType
    pure $
      Inline $
        mempty
          & nullable ?~ (G.unNullability nullability && G.isNullable subType)
          & type_ ?~ OpenApiArray
          & items ?~ OpenApiItemsObject st

-- TODO: No reference types should be nullable and only references to reference types

declareReference :: G.Nullability -> Text -> OMap.InsOrdHashMap Text (G.TypeDefinition a RemoteSchemaInputValueDefinition) -> Declare (Definitions Schema) ()
declareReference nullability n ts = do
  isAvailable <- referenceAvailable n
  unless isAvailable do
    for_ (OMap.lookup n ts) \t -> do
      let properties' = getPropertyReferences ts (typeProperties t)

      result <-
        declare $
          OMap.singleton n $
            let (refType, patt) = referenceType (null properties') (T.toLower n)
             in mempty
                  & nullable ?~ G.unNullability nullability
                  & description .~ typeDescription t
                  & properties .~ properties'
                  & type_ .~ refType
                  & setPattern patt
      void $ processProperties ts (typeProperties t)
      pure result

referenceAvailable :: Text -> DeclareT (Definitions Schema) Identity Bool
referenceAvailable n = OMap.member n <$> look

getPropertyReferences :: InsOrdHashMap Text (G.TypeDefinition a RemoteSchemaInputValueDefinition) -> Maybe [RemoteSchemaInputValueDefinition] -> InsOrdHashMap Text (Referenced Schema)
getPropertyReferences _ Nothing = mempty
getPropertyReferences sd (Just ds) =
  let ds' = fmap (processProperty' sd) ds
   in OMap.fromList ds'

processProperty' :: InsOrdHashMap Text (G.TypeDefinition a RemoteSchemaInputValueDefinition) -> RemoteSchemaInputValueDefinition -> (Text, Referenced Schema)
processProperty' sd (RemoteSchemaInputValueDefinition d _preset) =
  let n = G._ivdName d
      t = G._ivdType d
      rt = handleRefType' sd t
   in (G.unName n, rt)

handleRefType' :: OMap.InsOrdHashMap Text (G.TypeDefinition a RemoteSchemaInputValueDefinition) -> G.GType -> Referenced Schema
handleRefType' sd = \case
  G.TypeNamed _nullability nameWrapper ->
    let n = G.unName nameWrapper
     in Ref $ Reference n
  G.TypeList nullability subType ->
    let st = handleRefType' sd subType
     in Inline $
          mempty
            & nullable ?~ (G.unNullability nullability && G.isNullable subType)
            & type_ ?~ OpenApiArray
            & items ?~ OpenApiItemsObject st

typeDescription :: G.TypeDefinition possibleTypes inputType -> Maybe Text
typeDescription = \case
  (G.TypeDefinitionScalar o) -> G.unDescription <$> G._stdDescription o
  (G.TypeDefinitionObject o) -> G.unDescription <$> G._otdDescription o
  (G.TypeDefinitionInterface o) -> G.unDescription <$> G._itdDescription o
  (G.TypeDefinitionUnion o) -> G.unDescription <$> G._utdDescription o
  (G.TypeDefinitionEnum o) -> G.unDescription <$> G._etdDescription o
  (G.TypeDefinitionInputObject o) -> G.unDescription <$> G._iotdDescription o

typeName :: G.TypeDefinition possibleTypes inputType -> Text
typeName = \case
  (G.TypeDefinitionScalar o) -> G.unName (G._stdName o)
  (G.TypeDefinitionObject o) -> G.unName (G._otdName o)
  (G.TypeDefinitionInterface o) -> G.unName (G._itdName o)
  (G.TypeDefinitionUnion o) -> G.unName (G._utdName o)
  (G.TypeDefinitionEnum o) -> G.unName (G._etdName o)
  (G.TypeDefinitionInputObject o) -> G.unName (G._iotdName o)

typeProperties :: G.TypeDefinition possibleTypes RemoteSchemaInputValueDefinition -> Maybe [RemoteSchemaInputValueDefinition]
typeProperties = \case
  (G.TypeDefinitionScalar _) -> Nothing
  (G.TypeDefinitionInterface _) -> Nothing
  (G.TypeDefinitionUnion _) -> Nothing
  (G.TypeDefinitionEnum _) -> Nothing
  (G.TypeDefinitionInputObject o) -> Just $ G._iotdValueDefinitions o
  (G.TypeDefinitionObject _) -> Nothing

-- TODO: Can we reuse something from rest module to handle this?
-- TODO: referenceType could be improved, instead of using Bool (to indicate if it is object or scalar),
--        we can do something better
referenceType :: Bool -> Text -> (Maybe OpenApiType, Maybe Pattern)
referenceType False = const (Just OpenApiObject, Nothing)
referenceType True = \case
  "int" -> (Just OpenApiInteger, Nothing)
  "float" -> (Just OpenApiNumber, Nothing)
  "double" -> (Just OpenApiNumber, Nothing)
  "uuid" -> (Just OpenApiString, Just "[a-f0-9]{8}-[a-f0-9]{4}-4[a-f0-9]{3}-[89aAbB][a-f0-9]{3}-[a-f0-9]{12}")
  "bool" -> (Just OpenApiBoolean, Nothing)
  "boolean" -> (Just OpenApiBoolean, Nothing)
  "string" -> (Just OpenApiString, Nothing)
  "id" -> (Just OpenApiString, Nothing)
  _ -> (Nothing, Nothing)

processProperties :: InsOrdHashMap Text (G.TypeDefinition a RemoteSchemaInputValueDefinition) -> Maybe [RemoteSchemaInputValueDefinition] -> DeclareT (Definitions Schema) Identity (InsOrdHashMap Text (Referenced Schema))
processProperties _ Nothing = pure mempty
processProperties sd (Just ds) = do
  ds' <- traverse (processProperty sd) ds
  pure $ OMap.fromList ds'

processProperty :: InsOrdHashMap Text (G.TypeDefinition a RemoteSchemaInputValueDefinition) -> RemoteSchemaInputValueDefinition -> DeclareT (Definitions Schema) Identity (Text, Referenced Schema)
processProperty sd (RemoteSchemaInputValueDefinition d _preset) = do
  let n = G._ivdName d
      t = G._ivdType d
  rt <- handleRefType sd t
  pure (G.unName n, rt)

getGQLQueryFromTrie :: EndpointMetadata GQLQueryWithText -> Text
getGQLQueryFromTrie = getGQLQueryText . _edQuery . _ceDefinition

mkParam :: Text -> Maybe Text -> Maybe Bool -> ParamLocation -> Maybe Bool -> Maybe J.Value -> Maybe OpenApiType -> Maybe Pattern -> Param
mkParam nameP desc req loc allowEmpty def varType patt =
  mempty
    & name .~ nameP
    & description .~ desc
    & required .~ req
    & in_ .~ loc
    & allowEmptyValue .~ allowEmpty
    & schema
      ?~ Inline
        ( mempty
            & default_ .~ def
            & type_ .~ varType
            & setPattern patt
        )

gqlToJsonValue :: G.Value Void -> J.Value
gqlToJsonValue = \case
  G.VNull -> J.Null
  G.VInt n -> J.toJSON n
  G.VFloat sci -> J.toJSON sci
  G.VString txt -> J.toJSON txt
  G.VBoolean b -> J.toJSON b
  G.VEnum ev -> J.toJSON ev
  G.VList lst -> J.toJSON $ gqlToJsonValue <$> lst
  G.VObject obj -> J.toJSON $ gqlToJsonValue <$> obj

-- * Top level schema construction

getComment :: EndpointMetadata GQLQueryWithText -> Text
getComment d = comment
  where
    gql = getGQLQueryFromTrie d
    comment = case _ceComment d of
      (Just c) -> c <> "\n***\nThe GraphQl query for this endpoint is:\n``` graphql\n" <> gql <> "\n```"
      Nothing -> "***\nThe GraphQl query for this endpoint is:\n``` graphql\n" <> gql <> "\n```"

getURL :: EndpointMetadata GQLQueryWithText -> Text
getURL d =
  "/api/rest/" <> T.intercalate "/" pathComponents
  where
    pathComponents = splitPath formatVariable id . _ceUrl $ d
    formatVariable variable = "{" <> dropColonPrefix variable <> "}"
    dropColonPrefix = T.drop 1

extractEndpointInfo :: Maybe RemoteSchemaIntrospection -> EndpointMethod -> EndpointMetadata GQLQueryWithText -> Declare (Definitions Schema) EndpointData
extractEndpointInfo sd method d = do
  _edProperties <- mkProperties sd _analysis
  _edResponse <- mkResponse _edMethod _edUrl sd _analysis
  pure EndpointData {..}
  where
    _eDef = mdDefinitions d
    -- mdDefinition returns a list, but there should only be one definition associated, so it is safe to fold
    _analysis = fromMaybe mempty (fold $ mapMaybe (\e -> fmap (analyzeGraphqlQuery e) sd) _eDef)
    _edUrl = T.unpack . getURL $ d
    _edVarList = getParams _analysis (_ceUrl d)
    _edDescription = getComment d
    _edName = unNonEmptyText $ unEndpointName $ _ceName d
    _edMethod = [unEndpointMethod method] -- NOTE: Methods are grouped with into matching endpoints - Name used for grouping.

getEndpointsData :: Maybe RemoteSchemaIntrospection -> SchemaCache -> Declare (Definitions Schema) [EndpointData]
getEndpointsData sd sc = do
  let endpointTrie = scEndpoints sc
      methodMaps = leaves endpointTrie
      endpointsWithMethods = concatMap (\(m, s) -> map (m,) (Set.toList s)) $ concatMap (Map.toList . _unMultiMap) methodMaps

  endpointsWithInfo <- traverse (uncurry (extractEndpointInfo sd)) endpointsWithMethods

  let endpointsGrouped = NE.groupBy (\a b -> _edName a == _edName b) endpointsWithInfo

  pure $ map squashEndpointGroup endpointsGrouped

squashEndpointGroup :: NonEmpty EndpointData -> EndpointData
squashEndpointGroup g = (NE.head g) {_edMethod = concatMap _edMethod g}

getSchemaIntrospection :: SchemaCache -> Maybe RemoteSchemaIntrospection
getSchemaIntrospection SchemaCache {..} = do
  RoleContext {..} <- Map.lookup adminRoleName scGQLContext
  fieldMap <- either (const Nothing) Just $ gqlQueryParser _rctxDefault $ fmap (fmap nameToVariable) $ G._todSelectionSet $ _grQuery introspectionQuery
  RFRaw v <- OMap.lookup (mkUnNamespacedRootFieldAlias $$(G.litName "__schema")) fieldMap
  fmap irDoc $ parseIntrospectionResult $ J.object [("data", J.object [("__schema", JO.fromOrdered v)])]
  where
    -- This value isn't used but we give it a type to be more clear about what is being ignored
    nameToVariable :: G.Name -> Variable
    nameToVariable = undefined

serveJSON :: SchemaCache -> OpenApi
serveJSON sc = spec & components . schemas .~ defs
  where
    (defs, spec) = runDeclare (declareOpenApiSpec sc) mempty

-- | If all variables are scalar or optional then the entire request body can be marked as optional
isRequestBodyRequired :: EndpointData -> Bool
isRequestBodyRequired ed = not $ all isNotRequired (_edProperties ed)
  where
    -- The use of isNotRequired here won't work with list types since they are inline, but contain references
    isNotRequired (Inline Schema {..}) = isScalarType _schemaType || (Just True == _schemaNullable)
    isNotRequired (Ref _) = False -- Not all `Ref` are non nullable, imagine two endpoints using the same Ref one being nullable and other not
    isScalarType :: Maybe OpenApiType -> Bool
    isScalarType Nothing = False
    isScalarType (Just t) = case t of
      OpenApiString -> True
      OpenApiNumber -> True
      OpenApiInteger -> True
      OpenApiBoolean -> True
      OpenApiArray -> False
      OpenApiNull -> False
      OpenApiObject -> False

-- * Entry point

declareOpenApiSpec :: SchemaCache -> Declare (Definitions Schema) OpenApi
declareOpenApiSpec sc = do
  let _schemaIntrospection = getSchemaIntrospection sc
      warnings = case _schemaIntrospection of
        Nothing -> "\n\n⚠️ Schema introspection failed"
        _ -> ""

      mkRequestBody :: EndpointData -> RequestBody
      mkRequestBody ed =
        mempty
          & description ?~ "Query parameters can also be provided in the request body as a JSON object"
          & required ?~ isRequestBodyRequired ed
          & content
            .~ OMap.singleton
              ("application" // "json")
              ( mempty
                  & schema
                    ?~ Inline
                      ( mempty
                          & type_ ?~ OpenApiObject
                          & properties .~ _edProperties ed
                      )
              )

      mkOperation :: EndpointData -> Operation
      mkOperation ed =
        mempty
          & description ?~ _edDescription ed
          & summary ?~ _edName ed
          & parameters .~ (Inline xHasuraAdminSecret : _edVarList ed)
          & requestBody .~ toMaybe (not (null (_edProperties ed))) (Inline (mkRequestBody ed))
          & responses .~ Responses Nothing (maybe mempty (OMap.singleton 200 . Inline) (_edResponse ed))
        where
          toMaybe b a = if b then Just a else Nothing

      getOPName :: EndpointData -> Text -> Maybe Operation
      getOPName ed methodType =
        if methodType `elem` _edMethod ed
          then Just $ mkOperation ed
          else Nothing

      xHasuraAdminSecret :: Param
      xHasuraAdminSecret =
        mkParam
          "x-hasura-admin-secret"
          (Just "Your x-hasura-admin-secret will be used for authentication of the API request.")
          Nothing
          ParamHeader
          Nothing
          Nothing
          (Just OpenApiString)
          Nothing

      generatePathItem :: EndpointData -> PathItem
      generatePathItem ed =
        let pathData =
              mempty
                & get .~ getOPName ed "GET"
                & post .~ getOPName ed "POST"
                & put .~ getOPName ed "PUT"
                & delete .~ getOPName ed "DELETE"
                & patch .~ getOPName ed "PATCH"
            completePathData =
              if pathData == mempty
                then
                  mempty
                    & post
                      ?~ mkOperation
                        ed
                          { _edDescription =
                              "⚠️ Method("
                                <> tshow (_edMethod ed)
                                <> ") not supported, defaulting to POST\n\n"
                                <> _edDescription ed
                          }
                else pathData
         in completePathData

  endpointLst <- getEndpointsData _schemaIntrospection sc

  let mkOpenAPISchema :: [EndpointData] -> InsOrdHashMap FilePath PathItem
      mkOpenAPISchema edLst = foldl (\hm ed -> OMap.insertWith (<>) (_edUrl ed) (generatePathItem ed) hm) mempty edLst

      openAPIPaths = mkOpenAPISchema endpointLst

  return $
    mempty
      & paths .~ openAPIPaths
      & info . title .~ "Rest Endpoints"
      & info . description ?~ "This OpenAPI specification is automatically generated by Hasura." <> warnings