Core.hs

module Hasql.Session.Core where

import Hasql.Connection.Core qualified as Connection
import Hasql.Decoders.All qualified as Decoders
import Hasql.Decoders.Result qualified as Decoders.Result
import Hasql.Decoders.Results qualified as Decoders.Results
import Hasql.Encoders.All qualified as Encoders
import Hasql.Encoders.Params qualified as Encoders.Params
import Hasql.Errors
import Hasql.IO qualified as IO
import Hasql.LibPq14 qualified as Pq
import Hasql.Pipeline.Core qualified as Pipeline
import Hasql.Prelude
import Hasql.Statement qualified as Statement

-- |
-- A batch of actions to be executed in the context of a database connection.
newtype Session a
  = Session (ReaderT Connection.Connection (ExceptT SessionError IO) a)
  deriving (Functor, Applicative, Monad, MonadError SessionError, MonadIO, MonadReader Connection.Connection)

-- |
-- Executes a bunch of commands on the provided connection.
run :: Session a -> Connection.Connection -> IO (Either SessionError a)
run (Session impl) connection =
  handle @SomeException onExc
    $ runExceptT
    $ runReaderT impl connection
  where
    onExc exc =
      case connection of
        Connection.Connection pqConnVar _ _ ->
          withMVar pqConnVar onPqConn
      where
        onPqConn pqConn = do
          Pq.transactionStatus pqConn >>= \case
            Pq.TransIdle -> pure ()
            _ -> Pq.reset pqConn
          throwIO exc

-- |
-- Possibly a multi-statement query,
-- which however cannot be parameterized or prepared,
-- nor can any results of it be collected.
sql :: ByteString -> Session ()
sql sql =
  Session
    $ ReaderT
    $ \(Connection.Connection pqConnectionRef integerDatetimes registry) ->
      ExceptT
        $ fmap (first (QueryError sql []))
        $ withMVar pqConnectionRef
        $ \pqConnection -> do
          r1 <- IO.sendNonparametricStatement pqConnection sql
          r2 <- IO.getResults pqConnection integerDatetimes decoder
          return $ r1 *> r2
  where
    decoder =
      Decoders.Results.single Decoders.Result.noResult

-- |
-- Execute a statement by providing parameters to it.
statement :: params -> Statement.Statement params result -> Session result
statement input (Statement.Statement template (Encoders.Params paramsEncoder) (Decoders.Result decoder) preparable) =
  Session
    $ ReaderT
    $ \(Connection.Connection pqConnectionRef integerDatetimes registry) ->
      ExceptT
        $ fmap (first (QueryError template (Encoders.Params.renderReadable paramsEncoder input)))
        $ withMVar pqConnectionRef
        $ \pqConnection -> do
          r1 <- IO.sendParametricStatement pqConnection integerDatetimes registry template paramsEncoder preparable input
          r2 <- IO.getResults pqConnection integerDatetimes decoder
          return $ r1 *> r2

-- |
-- Execute a pipeline.
pipeline :: Pipeline.Pipeline result -> Session result
pipeline pipeline =
  Session $ ReaderT \(Connection.Connection pqConnectionRef integerDatetimes registry) ->
    ExceptT $ withMVar pqConnectionRef \pqConnection ->
      Pipeline.run pipeline pqConnection registry integerDatetimes