graphql-engine/server/src-lib/Hasura/SQL/Backend.hs

{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE QuasiQuotes #-}

module Hasura.SQL.Backend
  ( PostgresKind (..),
    BackendType (..),
    BackendSourceKind (..),
    backendShortName,
    supportedBackends,
    backendTextNames,
    backendTypeFromText,
    parseBackendTypeFromText,
    backendTypeFromBackendSourceKind,
  )
where

import Autodocodec (HasCodec (codec), JSONCodec, bimapCodec, dimapCodec, literalTextCodec, parseAlternatives)
import Data.Aeson
import Data.Aeson.Types (Parser)
import Data.Proxy
import Data.Text (unpack)
import Data.Text.Extended
import Data.Text.NonEmpty (NonEmptyText, mkNonEmptyText, nonEmptyTextCodec, nonEmptyTextQQ)
import Hasura.Backends.DataConnector.Adapter.Types (DataConnectorName (..))
import Hasura.Incremental
import Hasura.Prelude
import Witch qualified

-- | Argument to Postgres; we represent backends which are variations on Postgres as sub-types of
-- Postgres. This value indicates which "flavour" of Postgres a backend is.
data PostgresKind
  = Vanilla
  | Citus
  | Cockroach
  deriving stock (Show, Eq, Ord, Generic)
  deriving anyclass (Hashable, Cacheable)

-- | An enum that represents each backend we support.
data BackendType
  = Postgres PostgresKind
  | MSSQL
  | BigQuery
  | MySQL
  | DataConnector
  deriving stock (Show, Eq, Ord, Generic)
  deriving anyclass (Hashable, Cacheable)

-- | The name of the backend, as we expect it to appear in our metadata and API.
instance Witch.From BackendType NonEmptyText where
  from (Postgres Vanilla) = [nonEmptyTextQQ|postgres|]
  from (Postgres Citus) = [nonEmptyTextQQ|citus|]
  from (Postgres Cockroach) = [nonEmptyTextQQ|cockroach|]
  from MSSQL = [nonEmptyTextQQ|mssql|]
  from BigQuery = [nonEmptyTextQQ|bigquery|]
  from MySQL = [nonEmptyTextQQ|mysql|]
  from DataConnector = [nonEmptyTextQQ|dataconnector|]

instance ToTxt BackendType where
  toTxt = toTxt . Witch.into @NonEmptyText

instance FromJSON BackendType where
  parseJSON = withText "backend type" parseBackendTypeFromText

instance ToJSON BackendType where
  toJSON = String . toTxt

instance Cacheable (Proxy (b :: BackendType))

-- | Similar to 'BackendType', however, in the case of 'DataConnectorKind' we need to be able
-- capture the name of the data connector that should be used by the DataConnector backend.
-- This type correlates to the kind property of 'SourceMetadata', which is usually just
-- postgres, mssql, etc for static backends, but can be a configurable value for DataConnector
-- hence requiring 'DataConnectorName' for 'DataConnectorKind'
--
-- This type cannot entirely replace 'BackendType' because 'BackendType' has a fixed number of
-- possible values which can be enumerated over at compile time, but 'BackendSourceKind' does
-- not because DataConnector fundamentally is configured at runtime with 'DataConnectorName'.
data BackendSourceKind (b :: BackendType) where
  PostgresVanillaKind :: BackendSourceKind ('Postgres 'Vanilla)
  PostgresCitusKind :: BackendSourceKind ('Postgres 'Citus)
  PostgresCockroachKind :: BackendSourceKind ('Postgres 'Cockroach)
  MSSQLKind :: BackendSourceKind 'MSSQL
  BigQueryKind :: BackendSourceKind 'BigQuery
  MySQLKind :: BackendSourceKind 'MySQL
  DataConnectorKind :: DataConnectorName -> BackendSourceKind 'DataConnector

deriving instance Show (BackendSourceKind b)

deriving instance Eq (BackendSourceKind b)

deriving instance Ord (BackendSourceKind b)

instance Cacheable (BackendSourceKind b) where
  unchanged _ = (==)

instance Witch.From (BackendSourceKind b) NonEmptyText where
  -- All cases are specified explicitly here to ensure compiler warnings highlight
  -- this area for consideration and update if another BackendType is added
  from k@PostgresVanillaKind = Witch.into @NonEmptyText $ backendTypeFromBackendSourceKind k
  from k@PostgresCitusKind = Witch.into @NonEmptyText $ backendTypeFromBackendSourceKind k
  from k@PostgresCockroachKind = Witch.into @NonEmptyText $ backendTypeFromBackendSourceKind k
  from k@MSSQLKind = Witch.into @NonEmptyText $ backendTypeFromBackendSourceKind k
  from k@BigQueryKind = Witch.into @NonEmptyText $ backendTypeFromBackendSourceKind k
  from k@MySQLKind = Witch.into @NonEmptyText $ backendTypeFromBackendSourceKind k
  from (DataConnectorKind dataConnectorName) = Witch.into @NonEmptyText dataConnectorName

instance ToTxt (BackendSourceKind b) where
  toTxt = toTxt . Witch.into @NonEmptyText

-- If you need to parse an arbitrary string into a BackendSourceKind, you can't because of the
-- b type parameter. You actually want to parse into 'AnyBackend BackendSourceKind'.
-- See 'backendSourceKindFromText' from the AnyBackend module for that.

instance ToJSON (BackendSourceKind b) where
  toJSON = String . toTxt

instance FromJSON (BackendSourceKind ('Postgres 'Vanilla)) where
  parseJSON = mkParseStaticBackendSourceKind PostgresVanillaKind

instance FromJSON (BackendSourceKind ('Postgres 'Citus)) where
  parseJSON = mkParseStaticBackendSourceKind PostgresCitusKind

instance FromJSON (BackendSourceKind ('Postgres 'Cockroach)) where
  parseJSON = mkParseStaticBackendSourceKind PostgresCockroachKind

instance FromJSON (BackendSourceKind ('MSSQL)) where
  parseJSON = mkParseStaticBackendSourceKind MSSQLKind

instance FromJSON (BackendSourceKind ('BigQuery)) where
  parseJSON = mkParseStaticBackendSourceKind BigQueryKind

instance FromJSON (BackendSourceKind ('MySQL)) where
  parseJSON = mkParseStaticBackendSourceKind MySQLKind

instance FromJSON (BackendSourceKind ('DataConnector)) where
  parseJSON = withText "BackendSourceKind" $ \text ->
    DataConnectorKind . DataConnectorName <$> mkNonEmptyText text
      `onNothing` fail "Cannot be empty string"

mkParseStaticBackendSourceKind :: BackendSourceKind b -> (Value -> Parser (BackendSourceKind b))
mkParseStaticBackendSourceKind backendSourceKind =
  withText "BackendSourceKind" $ \text ->
    if text `elem` validValues
      then pure backendSourceKind
      else fail ("got: " <> unpack text <> ", expected one of: " <> unpack (commaSeparated validValues))
  where
    validValues = backendTextNames $ backendTypeFromBackendSourceKind backendSourceKind

instance HasCodec (BackendSourceKind ('Postgres 'Vanilla)) where
  codec = mkCodecStaticBackendSourceKind PostgresVanillaKind

instance HasCodec (BackendSourceKind ('Postgres 'Citus)) where
  codec = mkCodecStaticBackendSourceKind PostgresCitusKind

instance HasCodec (BackendSourceKind ('Postgres 'Cockroach)) where
  codec = mkCodecStaticBackendSourceKind PostgresCockroachKind

instance HasCodec (BackendSourceKind ('MSSQL)) where
  codec = mkCodecStaticBackendSourceKind MSSQLKind

instance HasCodec (BackendSourceKind ('BigQuery)) where
  codec = mkCodecStaticBackendSourceKind BigQueryKind

instance HasCodec (BackendSourceKind ('MySQL)) where
  codec = mkCodecStaticBackendSourceKind MySQLKind

instance HasCodec (BackendSourceKind ('DataConnector)) where
  codec = dimapCodec dec enc nonEmptyTextCodec
    where
      dec = DataConnectorKind . DataConnectorName
      enc = Witch.into

mkCodecStaticBackendSourceKind :: BackendSourceKind b -> JSONCodec (BackendSourceKind b)
mkCodecStaticBackendSourceKind backendSourceKind =
  bimapCodec dec enc $
    parseAlternatives (literalTextCodec longName) (literalTextCodec <$> aliases)
  where
    dec text =
      if text `elem` validValues
        then Right backendSourceKind
        else Left ("got: " <> unpack text <> ", expected one of: " <> unpack (commaSeparated validValues))

    enc = toTxt

    validValues = backendTextNames $ backendTypeFromBackendSourceKind backendSourceKind
    longName = head validValues
    aliases = tail validValues

-- | Some generated APIs use a shortened version of the backend's name rather than its full
-- name. This function returns the "short form" of a backend, if any.
backendShortName :: BackendType -> Maybe Text
backendShortName = \case
  Postgres Vanilla -> Just "pg"
  _ -> Nothing

supportedBackends :: [BackendType]
supportedBackends =
  [ Postgres Vanilla,
    Postgres Citus,
    Postgres Cockroach,
    MSSQL,
    BigQuery,
    MySQL,
    DataConnector
  ]

backendTextNames :: BackendType -> [Text]
backendTextNames b =
  catMaybes
    [ Just (toTxt b), -- long form
      backendShortName b -- short form
    ]

backendTextNameLookup :: [(Text, BackendType)]
backendTextNameLookup =
  supportedBackends >>= (\b -> (,b) <$> backendTextNames b)

-- | This uses this lookup mechanism to avoid having to duplicate and hardcode the
-- backend string. We accept both the short form and the long form of the backend's name.
backendTypeFromText :: Text -> Maybe BackendType
backendTypeFromText txt =
  lookup txt backendTextNameLookup

parseBackendTypeFromText :: Text -> Parser BackendType
parseBackendTypeFromText txt =
  let uniqueBackends = commaSeparated $ fst <$> backendTextNameLookup
   in backendTypeFromText txt
        `onNothing` fail ("got: " <> unpack txt <> ", expected one of: " <> unpack uniqueBackends)

backendTypeFromBackendSourceKind :: BackendSourceKind b -> BackendType
backendTypeFromBackendSourceKind = \case
  PostgresVanillaKind -> Postgres Vanilla
  PostgresCitusKind -> Postgres Citus
  PostgresCockroachKind -> Postgres Cockroach
  MSSQLKind -> MSSQL
  BigQueryKind -> BigQuery
  MySQLKind -> MySQL
  DataConnectorKind _ -> DataConnector