{-# LANGUAGE DisambiguateRecordFields #-}
{-# LANGUAGE DuplicateRecordFields    #-}

module Hasura.Backends.BigQuery.DDL.Source
  ( resolveSource
  , postDropSourceHook
  , resolveSourceConfig
  )
where

import           Hasura.Prelude

import qualified Data.Environment                         as Env
import qualified Data.HashMap.Strict                      as HM
import qualified Data.Text                                as T

import           Control.Concurrent.MVar                  (newMVar)
import           Data.Time.Clock.System

import           Hasura.Backends.BigQuery.Connection
import           Hasura.Backends.BigQuery.Instances.Types ()
import           Hasura.Backends.BigQuery.Meta
import           Hasura.Backends.BigQuery.Source
import           Hasura.Backends.BigQuery.Types
import           Hasura.Base.Error
import           Hasura.RQL.Types.Column
import           Hasura.RQL.Types.Common
import           Hasura.RQL.Types.Source
import           Hasura.RQL.Types.Table
import           Hasura.SQL.Backend
import           Hasura.Server.Types                      (MaintenanceMode)


resolveSourceConfig ::
  MonadIO m =>
  SourceName ->
  BigQueryConnSourceConfig ->
  m (Either QErr BigQuerySourceConfig)
resolveSourceConfig _name BigQueryConnSourceConfig{..} = runExceptT $ do
  env <- liftIO Env.getEnvironment
  eSA <- resolveConfigurationJson env _cscServiceAccount
  case eSA of
    Left e -> throw400 Unexpected $ T.pack e
    Right _scServiceAccount -> do
      _scDatasets <- resolveConfigurationInputs env _cscDatasets
      _scProjectId <- resolveConfigurationInput env _cscProjectId
      trMVar <- liftIO $ newMVar Nothing -- `runBigQuery` initializes the token
      pure BigQuerySourceConfig
             { _scAccessTokenMVar = trMVar
             , ..
             }


resolveSource
  :: (MonadIO m)
  => BigQuerySourceConfig
  -> MaintenanceMode
  -> m (Either QErr (ResolvedSource 'BigQuery))
resolveSource sourceConfig _maintenanceMode =
  runExceptT $ do
    result <- getTables sourceConfig
    case result of
      Left err ->
        throw400 Unexpected $
        "unexpected exception while connecting to database: " <> tshow err
      Right restTables -> do
        seconds <- liftIO $ fmap systemSeconds getSystemTime
        pure
          (ResolvedSource
             { _rsConfig = sourceConfig
             , _rsTables =
                 HM.fromList
                   [ ( restTableReferenceToTableName tableReference
                     , DBTableMetadata
                         { _ptmiOid = OID (fromIntegral seconds + index :: Int) -- TODO: The seconds are used for uniqueness. BigQuery doesn't support a "stable" ID for a table.
                         , _ptmiColumns =
                             [ RawColumnInfo
                               { prciName = ColumnName name
                               , prciPosition = position
                               , prciType = restTypeToScalarType type'
                               , prciIsNullable =
                                   case mode of
                                     Nullable -> True
                                     _        -> False
                               , prciDescription = Nothing
                               }
                             | (position, RestFieldSchema {name, type', mode}) <-
                                 zip [1 ..] fields -- TODO: Same trouble as Oid above.
                             ]
                         , _ptmiPrimaryKey = Nothing
                         , _ptmiUniqueConstraints = mempty
                         , _ptmiForeignKeys = mempty
                         , _ptmiViewInfo = Just $ ViewInfo False False False
                         , _ptmiDescription = Nothing
                         })
                   | (index, RestTable {tableReference, schema}) <-
                       zip [0 ..] restTables
                   , let RestTableSchema fields = schema
                   ]
             , _rsFunctions = mempty
             , _rsPgScalars = mempty
             })

restTypeToScalarType :: RestType -> ScalarType
restTypeToScalarType =
  \case
    STRING     -> StringScalarType
    BYTES      -> BytesScalarType
    INTEGER    -> IntegerScalarType
    FLOAT      -> FloatScalarType
    BOOL       -> BoolScalarType
    TIMESTAMP  -> TimestampScalarType
    DATE       -> DateScalarType
    TIME       -> TimeScalarType
    DATETIME   -> DatetimeScalarType
    GEOGRAPHY  -> GeographyScalarType
    STRUCT     -> StructScalarType
    BIGDECIMAL -> BigDecimalScalarType
    DECIMAL    -> DecimalScalarType

-- Hierarchy: Project / Dataset / Table
-- see <https://cloud.google.com/bigquery/docs/datasets-intro>
restTableReferenceToTableName :: RestTableReference -> TableName
restTableReferenceToTableName RestTableReference {..} =
  TableName {tableName = tableId, tableNameSchema = datasetId}
  -- We ignore project id and push that requirement up to the top to
  -- the data source level.

postDropSourceHook
  :: (MonadIO m)
  => BigQuerySourceConfig -> m ()
postDropSourceHook _ =
  -- On BigQuery we don't keep connections open.
  pure ()