-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/


-- | A high performance in memory and LevelDB backend for powerqueue
--   
--   A high performance in memory and LevelDB backend for powerqueue
@package powerqueue-levelmem
@version 0.1.1.0

module Data.PowerQueue.Backend.LevelMem

-- | Create a new data container for in memory job tracking and leveldb
--   disk persistence. Provide a <a>FilePath</a> for storing the data, an
--   <a>Int</a> as maximum queue size and a <a>JobEncoding</a> for
--   individual job encoding.
withLevelMem :: LevelMemCfg j -> (LevelMem j -> IO a) -> IO a
data LevelMemCfg j
LevelMemCfg :: !FilePath -> !Int -> !(JobEncoding j) -> !InProgressCfg -> LevelMemCfg j

-- | directory for persistence
[lmc_storageDir] :: LevelMemCfg j -> !FilePath

-- | maximum size of queue, succeeding enqueues will block
[lmc_maxQueueSize] :: LevelMemCfg j -> !Int

-- | binary encoding of jobs
[lmc_jobEncoding] :: LevelMemCfg j -> !(JobEncoding j)

-- | how should in progress jobs be handled after a restart while loading
--   from disk
[lmc_inProgressRecovery] :: LevelMemCfg j -> !InProgressCfg

-- | Behavoir for in progress jobs after loading the state from disk on
--   launch
data InProgressCfg

-- | mark the job as in progress
IpRecover :: InProgressCfg

-- | add the job to the queue
IpRestart :: InProgressCfg

-- | discard the job
IpForget :: InProgressCfg

-- | Binary encoding of a single job. Note that it is highly recommended to
--   use a backwards compatible decoder, otherwise the persistent state can
--   not be read. You could use safecopy or an appropriate cereal, binary,
--   aeson or other decoding.
data JobEncoding j
JobEncoding :: (j -> ByteString) -> (ByteString -> Either String j) -> JobEncoding j
[j_encode] :: JobEncoding j -> j -> ByteString
[j_decode] :: JobEncoding j -> ByteString -> Either String j

-- | The data container for tracking jobs and persisting them to disk
data LevelMem j
data JobStatus

-- | job is enqueued, not being worked on
JQueued :: JobStatus

-- | job currently being worked on
JInProgress :: JobStatus

-- | Get a snapshot of the current state of all jobs.
getJobStatusMap :: LevelMem j -> IO [(j, JobStatus)]

-- | Get the job status for a job. Note that this is a potentially
--   expensive operation as all known jobs must be traversed. A more
--   efficient handling would be to call <a>getJobStatusMap</a> once
--   beforce launching the worker and then tracking status manually within
--   the worker.
getJobStatus :: Eq j => j -> LevelMem j -> IO (Maybe JobStatus)

-- | Create a queue backend from <a>LevelMem</a>
newLevelMemBackend :: LevelMem j -> QueueBackend j
instance GHC.Classes.Eq Data.PowerQueue.Backend.LevelMem.JobStatus
instance GHC.Show.Show Data.PowerQueue.Backend.LevelMem.JobStatus