CustomTypes.hs

module Valiant.CLI.CustomTypes
  ( CustomTypeMap
  , loadCustomTypes
  , customTypesFile
  ) where

import Data.Aeson (FromJSON (..), eitherDecode, withObject, (.:))
import Data.ByteString.Lazy qualified as LBS
import Data.Map.Strict (Map)
import Data.Map.Strict qualified as Map
import Data.Text (Text)
import Data.Word (Word32)
import PgWire.Protocol.Oid (Oid (..))
import Valiant.CLI.TypeMap (HaskellType (..))
import System.Directory (doesFileExist)

-- | User-defined OID → Haskell type mappings.
type CustomTypeMap = Map Oid HaskellType

-- | Default file name for custom type mappings.
customTypesFile :: FilePath
customTypesFile = "valiant-types.json"

-- | Load custom type mappings from a JSON file if it exists.
-- Returns an empty map if the file is absent.
--
-- Expected format:
--
-- > [
-- >   { "oid": 600, "pg_type_name": "point", "haskell_type": "MyPoint", "haskell_module": "MyApp.Types" },
-- >   { "oid": 16389, "pg_type_name": "mood", "haskell_type": "Text", "haskell_module": "Data.Text" }
-- > ]
loadCustomTypes :: FilePath -> IO CustomTypeMap
loadCustomTypes path = do
  exists <- doesFileExist path
  if not exists
    then pure Map.empty
    else do
      bytes <- LBS.readFile path
      case eitherDecode bytes of
        Left _ -> pure Map.empty
        Right entries -> pure (toMap entries)

toMap :: [CustomTypeEntry] -> CustomTypeMap
toMap = Map.fromList . map toPair
  where
    toPair CustomTypeEntry {..} =
      (Oid cteOid, HaskellType cteHaskellType cteHaskellModule)

data CustomTypeEntry = CustomTypeEntry
  { cteOid :: Word32
  , ctePgTypeName :: Text
  , cteHaskellType :: Text
  , cteHaskellModule :: Text
  }

instance FromJSON CustomTypeEntry where
  parseJSON = withObject "CustomTypeEntry" $ \o ->
    CustomTypeEntry
      <$> o .: "oid"
      <*> o .: "pg_type_name"
      <*> o .: "haskell_type"
      <*> o .: "haskell_module"