{-# OPTIONS_GHC -fno-warn-orphans #-}

module Hasura.Backends.MSSQL.Instances.Schema () where

import           Hasura.Prelude

import qualified Data.HashMap.Strict                   as Map
import qualified Data.List.NonEmpty                    as NE
import qualified Database.ODBC.SQLServer               as ODBC
import qualified Language.GraphQL.Draft.Syntax         as G

import           Data.Text.Encoding                    (encodeUtf8)
import           Data.Text.Extended

import qualified Hasura.Backends.MSSQL.Types           as MSSQL
import qualified Hasura.GraphQL.Parser                 as P
import qualified Hasura.GraphQL.Schema.Build           as GSB
import qualified Hasura.RQL.IR.Select                  as IR
import qualified Hasura.RQL.IR.Update                  as IR

import           Hasura.GraphQL.Context
import           Hasura.GraphQL.Parser                 hiding (EnumValueInfo, field)
import           Hasura.GraphQL.Parser.Internal.Parser hiding (field)
import           Hasura.GraphQL.Schema.Backend
import           Hasura.GraphQL.Schema.Common
import           Hasura.RQL.Types


----------------------------------------------------------------
-- BackendSchema instance

instance BackendSchema 'MSSQL where
  -- top level parsers
  buildTableQueryFields          = GSB.buildTableQueryFields
  buildTableRelayQueryFields     = msBuildTableRelayQueryFields
  buildTableInsertMutationFields = msBuildTableInsertMutationFields
  buildTableUpdateMutationFields = msBuildTableUpdateMutationFields
  buildTableDeleteMutationFields = msBuildTableDeleteMutationFields
  buildFunctionQueryFields       = msBuildFunctionQueryFields
  buildFunctionRelayQueryFields  = msBuildFunctionRelayQueryFields
  buildFunctionMutationFields    = msBuildFunctionMutationFields
  -- backend extensions
  relayExtension    = const Nothing
  nodesAggExtension = const Nothing
  -- indivdual components
  columnParser              = msColumnParser
  jsonPathArg               = msJsonPathArg
  orderByOperators          = msOrderByOperators
  comparisonExps            = msComparisonExps
  updateOperators           = msUpdateOperators
  offsetParser              = msOffsetParser
  mkCountType               = msMkCountType
  aggregateOrderByCountType = MSSQL.IntegerType
  computedField             = msComputedField
  node                      = msNode
  tableDistinctOn           = msTableDistinctOn
  remoteRelationshipField   = msRemoteRelationshipField
  -- SQL literals
  columnDefaultValue = msColumnDefaultValue


----------------------------------------------------------------
-- Top level parsers

msBuildTableRelayQueryFields
  :: MonadBuildSchema 'MSSQL r m n
  => SourceName
  -> SourceConfig 'MSSQL
  -> TableName    'MSSQL
  -> TableInfo    'MSSQL
  -> G.Name
  -> NESeq (ColumnInfo 'MSSQL)
  -> SelPermInfo  'MSSQL
  -> m (Maybe (FieldParser n (QueryRootField UnpreparedValue)))
msBuildTableRelayQueryFields _sourceName _sourceInfo _tableName _tableInfo _gqlName _pkeyColumns _selPerms =
  pure Nothing

msBuildTableInsertMutationFields
  :: MonadBuildSchema 'MSSQL r m n
  => SourceName
  -> SourceConfig 'MSSQL
  -> TableName 'MSSQL
  -> TableInfo 'MSSQL
  -> G.Name
  -> InsPermInfo 'MSSQL
  -> Maybe (SelPermInfo 'MSSQL)
  -> Maybe (UpdPermInfo 'MSSQL)
  -> m [FieldParser n (MutationRootField UnpreparedValue)]
msBuildTableInsertMutationFields _sourceName _sourceInfo _tableName _tableInfo _gqlName _insPerms _selPerms _updPerms =
  pure []

msBuildTableUpdateMutationFields
  :: MonadBuildSchema 'MSSQL r m n
  => SourceName
  -> SourceConfig 'MSSQL
  -> TableName 'MSSQL
  -> TableInfo 'MSSQL
  -> G.Name
  -> UpdPermInfo 'MSSQL
  -> Maybe (SelPermInfo 'MSSQL)
  -> m [FieldParser n (MutationRootField UnpreparedValue)]
msBuildTableUpdateMutationFields _sourceName _sourceInfo _tableName _tableInfo _gqlName _updPerns _selPerms =
  pure []

msBuildTableDeleteMutationFields
  :: MonadBuildSchema 'MSSQL r m n
  => SourceName
  -> SourceConfig 'MSSQL
  -> TableName 'MSSQL
  -> TableInfo 'MSSQL
  -> G.Name
  -> DelPermInfo 'MSSQL
  -> Maybe (SelPermInfo 'MSSQL)
  -> m [FieldParser n (MutationRootField UnpreparedValue)]
msBuildTableDeleteMutationFields _sourceName _sourceInfo _tableName _tableInfo _gqlName _delPerns _selPerms =
  pure []

msBuildFunctionQueryFields
    :: MonadBuildSchema 'MSSQL r m n
    => SourceName
    -> SourceConfig 'MSSQL
    -> FunctionName 'MSSQL
    -> FunctionInfo 'MSSQL
    -> TableName 'MSSQL
    -> SelPermInfo 'MSSQL
    -> m [FieldParser n (QueryRootField UnpreparedValue)]
msBuildFunctionQueryFields _ _ _ _ _ _ =
  pure []

msBuildFunctionRelayQueryFields
  :: MonadBuildSchema 'MSSQL r m n
  => SourceName
  -> SourceConfig 'MSSQL
  -> FunctionName 'MSSQL
  -> FunctionInfo 'MSSQL
  -> TableName    'MSSQL
  -> NESeq (ColumnInfo 'MSSQL)
  -> SelPermInfo  'MSSQL
  -> m (Maybe (FieldParser n (QueryRootField UnpreparedValue)))
msBuildFunctionRelayQueryFields _sourceName _sourceInfo _functionName _functionInfo _tableName _pkeyColumns _selPerms =
  pure Nothing

msBuildFunctionMutationFields
    :: MonadBuildSchema 'MSSQL r m n
    => SourceName
    -> SourceConfig 'MSSQL
    -> FunctionName 'MSSQL
    -> FunctionInfo 'MSSQL
    -> TableName 'MSSQL
    -> SelPermInfo 'MSSQL
    -> m [FieldParser n (MutationRootField UnpreparedValue)]
msBuildFunctionMutationFields _ _ _ _ _ _ =
  pure []

mkMSSQLScalarTypeName :: MonadError QErr m => MSSQL.ScalarType -> m G.Name
mkMSSQLScalarTypeName = \case
  MSSQL.WcharType    -> pure stringScalar
  MSSQL.WvarcharType -> pure stringScalar
  MSSQL.WtextType    -> pure stringScalar
  MSSQL.FloatType    -> pure floatScalar
  -- integer types
  MSSQL.IntegerType  -> pure intScalar
  -- boolean type
  MSSQL.BitType      -> pure boolScalar
  scalarType -> G.mkName (MSSQL.scalarTypeDBName scalarType) `onNothing` throw400 ValidationFailed
    ("cannot use SQL type " <> scalarType <<> " in the GraphQL schema because its name is not a "
    <> "valid GraphQL identifier")

----------------------------------------------------------------
-- Individual components

msColumnParser
  :: (MonadSchema n m, MonadError QErr m)
  => ColumnType 'MSSQL
  -> G.Nullability
  -> m (Parser 'Both n (Opaque (ColumnValue 'MSSQL)))
msColumnParser columnType (G.Nullability isNullable) =
  opaque . fmap (ColumnValue columnType) <$> case columnType of
    ColumnScalar scalarType -> possiblyNullable scalarType <$> case scalarType of
      -- bytestring
      MSSQL.CharType     -> pure $ ODBC.ByteStringValue . encodeUtf8 <$> P.string
      MSSQL.VarcharType  -> pure $ ODBC.ByteStringValue . encodeUtf8 <$> P.string

      -- text
      MSSQL.WcharType    -> pure $ ODBC.TextValue <$> P.string
      MSSQL.WvarcharType -> pure $ ODBC.TextValue <$> P.string
      MSSQL.WtextType    -> pure $ ODBC.TextValue <$> P.string
      MSSQL.TextType     -> pure $ ODBC.TextValue <$> P.string

      -- integer
      MSSQL.IntegerType  -> pure $ ODBC.IntValue . fromIntegral <$> P.int
      MSSQL.SmallintType -> pure $ ODBC.IntValue . fromIntegral <$> P.int
      MSSQL.BigintType   -> pure $ ODBC.IntValue . fromIntegral <$> P.int
      MSSQL.TinyintType  -> pure $ ODBC.IntValue . fromIntegral <$> P.int

      -- float
      MSSQL.NumericType  -> pure $ ODBC.DoubleValue <$> P.float
      MSSQL.DecimalType  -> pure $ ODBC.DoubleValue <$> P.float
      MSSQL.FloatType    -> pure $ ODBC.DoubleValue <$> P.float
      MSSQL.RealType     -> pure $ ODBC.DoubleValue <$> P.float

      -- boolean
      MSSQL.BitType      -> pure $ ODBC.BoolValue <$> P.boolean
      _                  -> do
        name <- mkMSSQLScalarTypeName scalarType
        let schemaType = P.NonNullable $ P.TNamed $ P.mkDefinition name Nothing P.TIScalar
        pure $ Parser
          { pType = schemaType
          , pParser =
              valueToJSON (P.toGraphQLType schemaType) >=>
              either (parseErrorWith ParseFailed . qeError) pure . (MSSQL.parseScalarValue scalarType)
          }
    ColumnEnumReference (EnumReference tableName enumValues) ->
      case nonEmpty (Map.toList enumValues) of
        Just enumValuesList -> do
          tableGQLName <- tableGraphQLName tableName `onLeft` throwError
          let enumName = tableGQLName <> $$(G.litName "_enum")
          pure $ possiblyNullable MSSQL.VarcharType $ P.enum enumName Nothing (mkEnumValue <$> enumValuesList)
        Nothing -> throw400 ValidationFailed "empty enum values"
  where
    -- Sadly, this combinator is not sound in general, so we can’t export it
    -- for general-purpose use. If we did, someone could write this:
    --
    --   mkParameter <$> opaque do
    --     n <- int
    --     pure (mkIntColumnValue (n + 1))
    --
    -- Now we’d end up with a UVParameter that has a variable in it, so we’d
    -- parameterize over it. But when we’d reuse the plan, we wouldn’t know to
    -- increment the value by 1, so we’d use the wrong value!
    --
    -- We could theoretically solve this by retaining a reference to the parser
    -- itself and re-parsing each new value, using the saved parser, which
    -- would admittedly be neat. But it’s more complicated, and it isn’t clear
    -- that it would actually be useful, so for now we don’t support it.
    opaque :: MonadParse m => Parser 'Both m a -> Parser 'Both m (Opaque a)
    opaque parser = parser
      { pParser = \case
          P.GraphQLValue (G.VVariable var@Variable{ vInfo, vValue }) -> do
            typeCheck False (P.toGraphQLType $ pType parser) var
            P.mkOpaque (Just vInfo) <$> pParser parser (absurd <$> vValue)
          value -> P.mkOpaque Nothing <$> pParser parser value
      }
    possiblyNullable _scalarType
      | isNullable = fmap (fromMaybe ODBC.NullValue) . P.nullable
      | otherwise  = id
    mkEnumValue :: (EnumValue, EnumValueInfo) -> (P.Definition P.EnumValueInfo, ScalarValue 'MSSQL)
    mkEnumValue (EnumValue value, EnumValueInfo description) =
      ( P.mkDefinition value (G.Description <$> description) P.EnumValueInfo
      , ODBC.TextValue $ G.unName value
      )

msJsonPathArg
  :: MonadParse n
  => ColumnType 'MSSQL
  -> InputFieldsParser n (Maybe (IR.ColumnOp 'MSSQL))
msJsonPathArg _columnType = pure Nothing

msOrderByOperators
  :: NonEmpty
      ( Definition P.EnumValueInfo
      , (BasicOrderType 'MSSQL, NullsOrderType 'MSSQL)
      )
msOrderByOperators = NE.fromList
  [ ( define $$(G.litName "asc") "in ascending order, nulls first"
    , (MSSQL.AscOrder, MSSQL.NullsFirst)
    )
  , ( define $$(G.litName "asc_nulls_first") "in ascending order, nulls first"
    , (MSSQL.AscOrder, MSSQL.NullsFirst)
    )
  , ( define $$(G.litName "asc_nulls_last") "in ascending order, nulls last"
    , (MSSQL.AscOrder, MSSQL.NullsLast)
    )
  , ( define $$(G.litName "desc") "in descending order, nulls last"
    , (MSSQL.DescOrder, MSSQL.NullsLast)
    )
  , ( define $$(G.litName "desc_nulls_first") "in descending order, nulls first"
    , (MSSQL.DescOrder, MSSQL.NullsFirst)
    )
  , ( define $$(G.litName "desc_nulls_last") "in descending order, nulls last"
    , (MSSQL.DescOrder, MSSQL.NullsLast)
    )
  ]
  where
    define name desc = P.mkDefinition name (Just desc) P.EnumValueInfo

msComparisonExps
  :: forall m n
  . (BackendSchema 'MSSQL, MonadSchema n m, MonadError QErr m)
  => ColumnType 'MSSQL
  -> m (Parser 'Input n [ComparisonExp 'MSSQL])
msComparisonExps = P.memoize 'comparisonExps \columnType -> do
  -- see Note [Columns in comparison expression are never nullable]
  typedParser        <- columnParser columnType (G.Nullability False)
  nullableTextParser <- columnParser (ColumnScalar MSSQL.VarcharType) (G.Nullability True)
  textParser         <- columnParser (ColumnScalar MSSQL.VarcharType) (G.Nullability False)
  let name = P.getName typedParser <> $$(G.litName "_MSSQL_comparison_exp")
      desc = G.Description $ "Boolean expression to compare columns of type "
        <>  P.getName typedParser
        <<> ". All fields are combined with logical 'AND'."
      textListParser = P.list textParser `P.bind` traverse P.openOpaque
      columnListParser = P.list typedParser `P.bind` traverse P.openOpaque
  pure $ P.object name (Just desc) $ fmap catMaybes $ sequenceA $ concat
    [
    -- Common ops for all types
      [ P.fieldOptional $$(G.litName "_is_null") Nothing (bool ANISNOTNULL ANISNULL <$> P.boolean)
      , P.fieldOptional $$(G.litName "_eq")      Nothing (AEQ True . mkParameter <$> typedParser)
      , P.fieldOptional $$(G.litName "_neq")     Nothing (ANE True . mkParameter <$> typedParser)
      , P.fieldOptional $$(G.litName "_gt")      Nothing (AGT  . mkParameter <$> typedParser)
      , P.fieldOptional $$(G.litName "_lt")      Nothing (ALT  . mkParameter <$> typedParser)
      , P.fieldOptional $$(G.litName "_gte")     Nothing (AGTE . mkParameter <$> typedParser)
      , P.fieldOptional $$(G.litName "_lte")     Nothing (ALTE . mkParameter <$> typedParser)
      , P.fieldOptional $$(G.litName "_in")      Nothing (AIN . mkListLiteral <$> columnListParser)
      , P.fieldOptional $$(G.litName "_nin")     Nothing (ANIN . mkListLiteral <$> columnListParser)
      ]

    -- Ops for String like types
    , guard (isScalarColumnWhere (`elem` MSSQL.stringTypes) columnType) *>
      [ P.fieldOptional $$(G.litName "_like")
        (Just "does the column match the given pattern")
        (ALIKE     . mkParameter <$> typedParser)
      , P.fieldOptional $$(G.litName "_nlike")
        (Just "does the column NOT match the given pattern")
        (ANLIKE    . mkParameter <$> typedParser)
      ]
    ]
  where
    mkListLiteral :: [ColumnValue 'MSSQL] -> UnpreparedValue 'MSSQL
    mkListLiteral =
      P.UVLiteral . MSSQL.ListExpression . fmap (MSSQL.ValueExpression . cvValue)

msOffsetParser :: MonadParse n => Parser 'Both n (SQLExpression 'MSSQL)
msOffsetParser = MSSQL.ValueExpression . ODBC.IntValue . fromIntegral <$> P.int

msMkCountType
  :: Maybe Bool
  -- ^ distinct values
  -> Maybe [Column 'MSSQL]
  -> CountType 'MSSQL
msMkCountType _           Nothing     = MSSQL.StarCountable
msMkCountType (Just True) (Just cols) =
  maybe MSSQL.StarCountable MSSQL.DistinctCountable $ nonEmpty cols
msMkCountType _           (Just cols) =
  maybe MSSQL.StarCountable MSSQL.NonNullFieldCountable $ nonEmpty cols

-- | Argument to distinct select on columns returned from table selection
-- > distinct_on: [table_select_column!]
msTableDistinctOn
  -- :: forall m n. (BackendSchema 'MSSQL, MonadSchema n m, MonadTableInfo r m, MonadRole r m)
  :: Applicative m
  => Applicative n
  => TableName 'MSSQL
  -> SelPermInfo 'MSSQL
  -> m (InputFieldsParser n (Maybe (XDistinct 'MSSQL, NonEmpty (Column 'MSSQL))))
msTableDistinctOn _table _selectPermissions = pure (pure Nothing)

-- | Various update operators
msUpdateOperators
  -- :: forall m n r. (MonadSchema n m, MonadTableInfo r m)
  :: Applicative m
  => TableName 'MSSQL         -- ^ qualified name of the table
  -> UpdPermInfo 'MSSQL       -- ^ update permissions of the table
  -> m (Maybe (InputFieldsParser n [(Column 'MSSQL, IR.UpdOpExpG (UnpreparedValue 'MSSQL))]))
msUpdateOperators _table _updatePermissions = pure Nothing

-- | Computed field parser.
-- Currently unsupported: returns Nothing for now.
msComputedField
  :: MonadBuildSchema 'MSSQL r m n
  => ComputedFieldInfo 'MSSQL
  -> SelPermInfo 'MSSQL
  -> m (Maybe (FieldParser n (AnnotatedField 'MSSQL)))
msComputedField _fieldInfo _selectPemissions = pure Nothing

-- | Remote join field parser.
-- Currently unsupported: returns Nothing for now.
msRemoteRelationshipField
  :: MonadBuildSchema 'MSSQL r m n
  => RemoteFieldInfo 'MSSQL
  -> m (Maybe [FieldParser n (AnnotatedField 'MSSQL)])
msRemoteRelationshipField _remoteFieldInfo = pure Nothing

-- | The 'node' root field of a Relay request. Relay is currently unsupported on MSSQL,
-- meaning this parser will never be called: any attempt to create this parser should
-- therefore fail.
msNode
  :: MonadBuildSchema 'MSSQL r m n
  => m ( Parser 'Output n
         ( HashMap
           ( TableName 'MSSQL)
           ( SourceName, SourceConfig 'MSSQL
           , SelPermInfo 'MSSQL
           , PrimaryKeyColumns 'MSSQL
           , AnnotatedFields 'MSSQL
           )
         )
       )
msNode = throw500 "MSSQL does not support relay; `node` should never be exposed in the schema."


----------------------------------------------------------------
-- SQL literals

-- FIXME: this is nonsensical for MSSQL, we'll need to adjust the corresponding mutation
-- and its representation.
msColumnDefaultValue :: Column 'MSSQL -> SQLExpression 'MSSQL
msColumnDefaultValue = const $ MSSQL.ValueExpression ODBC.NullValue