-- |
-- Working example:
--
-- \$ curl -XPOST http://localhost:8080/v2/query -d @- <<EOF
-- {
--   "type":"bigquery_run_sql",
--   "args": {
--     "sql":"select 3 * 4 as foo, \"Hello, World!\" as bar",
--     "source":"chinook"
--   }
-- }
-- EOF
-- {"result_type":"TuplesOk","result":[["foo","bar"],["12","Hello, World!"]]}
module Hasura.Backends.BigQuery.DDL.RunSQL
  ( runSQL,
    runDatabaseInspection,
    BigQueryRunSQL,
  )
where

import Data.Aeson qualified as J
import Data.Aeson.TH (deriveJSON)
import Data.Aeson.Text (encodeToLazyText)
import Data.HashMap.Strict.InsOrd qualified as OMap
import Data.Text qualified as T
import Data.Text.Lazy qualified as LT
import Data.Vector qualified as V
import Hasura.Backends.BigQuery.Execute qualified as Execute
import Hasura.Backends.BigQuery.Source (BigQuerySourceConfig (..))
import Hasura.Backends.BigQuery.Types qualified as BigQuery
import Hasura.Base.Error
import Hasura.EncJSON
import Hasura.Prelude
import Hasura.RQL.DDL.Schema (RunSQLRes (..))
import Hasura.RQL.Types (CacheRWM, MetadataM, SourceName, askSourceConfig)
import Hasura.SQL.Backend

data BigQueryRunSQL = BigQueryRunSQL
  { _mrsSql :: Text,
    _mrsSource :: !SourceName
  }
  deriving (Show, Eq)

$(deriveJSON hasuraJSON ''BigQueryRunSQL)

runSQL ::
  (MonadIO m, CacheRWM m, MonadError QErr m, MetadataM m) =>
  BigQueryRunSQL ->
  m EncJSON
runSQL = runSQL_ recordSetAsHeaderAndRows

-- | The SQL query in the request is ignored
runDatabaseInspection ::
  (MonadIO m, CacheRWM m, MonadError QErr m, MetadataM m) =>
  BigQueryRunSQL ->
  m EncJSON
runDatabaseInspection (BigQueryRunSQL _query source) = do
  BigQuerySourceConfig {_scDatasets = dataSets} <- askSourceConfig @'BigQuery source
  let queries =
        [ "SELECT *, ARRAY(SELECT as STRUCT * from "
            <> dataSet
            <> ".INFORMATION_SCHEMA.COLUMNS WHERE table_name = t.table_name) as columns from "
            <> dataSet
            <> ".INFORMATION_SCHEMA.TABLES as t"
          | dataSet <- dataSets
        ]
      query' = T.intercalate " UNION ALL " queries
  runSQL_ recordSetAsSchema (BigQueryRunSQL query' source)

runSQL_ ::
  (MonadIO m, CacheRWM m, MonadError QErr m, MetadataM m) =>
  (Execute.RecordSet -> J.Value) ->
  BigQueryRunSQL ->
  m EncJSON
runSQL_ f (BigQueryRunSQL query source) = do
  sourceConfig <- askSourceConfig @'BigQuery source
  result <-
    Execute.streamBigQuery
      sourceConfig
      Execute.BigQuery {query = LT.fromStrict query, parameters = mempty, cardinality = BigQuery.Many}
  case result of
    Left queryError -> throw400 BigQueryError (tshow queryError) -- TODO: Pretty print the error type.
    Right recordSet ->
      pure
        ( encJFromJValue
            (RunSQLRes "TuplesOk" (f recordSet))
        )

recordSetAsHeaderAndRows :: Execute.RecordSet -> J.Value
recordSetAsHeaderAndRows Execute.RecordSet {rows} = J.toJSON (thead : tbody)
  where
    thead =
      case rows V.!? 0 of
        Nothing -> []
        Just row ->
          map (J.toJSON . (coerce :: Execute.FieldNameText -> Text)) (OMap.keys row)
    tbody :: [[J.Value]]
    tbody = map (\row -> map J.toJSON (OMap.elems row)) (toList rows)

recordSetAsSchema :: Execute.RecordSet -> J.Value
recordSetAsSchema rs@(Execute.RecordSet {rows}) =
  recordSetAsHeaderAndRows $
    rs
      { Execute.rows =
          OMap.adjust
            (Execute.TextOutputValue . LT.toStrict . encodeToLazyText . J.toJSON)
            (Execute.FieldNameText "columns")
            <$> rows
      }