module Database.PostgreSQL.Consumers.Consumer (
    ConsumerID
  , registerConsumer
  , unregisterConsumer
  ) where

import Control.Applicative
import Control.Monad.Base
import Control.Monad.Catch
import Control.Monad.Time
import Data.Int
import Data.Monoid
import Data.Monoid.Utils
import Database.PostgreSQL.PQTypes
import Prelude

import Database.PostgreSQL.Consumers.Config

-- | ID of a consumer.
newtype ConsumerID = ConsumerID Int64
  deriving (Eq, Ord, PQFormat)
instance FromSQL ConsumerID where
  type PQBase ConsumerID = PQBase Int64
  fromSQL mbase = ConsumerID <$> fromSQL mbase
instance ToSQL ConsumerID where
  type PQDest ConsumerID = PQDest Int64
  toSQL (ConsumerID n) = toSQL n

instance Show ConsumerID where
  showsPrec p (ConsumerID n) = showsPrec p n
 
-- | Register consumer in the consumers table,
-- so that it can reserve jobs using acquired ID.
registerConsumer
  :: (MonadBase IO m, MonadMask m, MonadTime m)
  => ConsumerConfig n idx job
  -> ConnectionSourceM m
  -> m ConsumerID
registerConsumer ConsumerConfig{..} cs = runDBT cs ts $ do
  now <- currentTime
  runSQL_ $ smconcat [
      "INSERT INTO" <+> raw ccConsumersTable
    , "(name, last_activity) VALUES (" <?> unRawSQL ccJobsTable <> ", " <?> now <> ")"
    , "RETURNING id"
    ]
  fetchOne runIdentity
  where
    ts = def {
      tsAutoTransaction = False
    }

-- | Unregister consumer with a given ID.
unregisterConsumer
  :: (MonadBase IO m, MonadMask m)
  => ConsumerConfig n idx job
  -> ConnectionSourceM m
  -> ConsumerID
  -> m ()
unregisterConsumer ConsumerConfig{..} cs wid = runDBT cs ts $ do
  -- Free tasks manually in case there is no
  -- foreign key constraint on reserved_by,
  runSQL_ $ smconcat [
      "UPDATE" <+> raw ccJobsTable
    , "   SET reserved_by = NULL"
    , " WHERE reserved_by =" <?> wid
    ]
  runSQL_ $ smconcat [
      "DELETE FROM " <+> raw ccConsumersTable
    , "WHERE id =" <?> wid
    , "  AND name =" <?> unRawSQL ccJobsTable
    ]
  where
    ts = def {
      tsRestartPredicate = Just . RestartPredicate
      $ \e _ -> qeErrorCode e == DeadlockDetected
    }