{-# LANGUAGE MultiWayIf, FunctionalDependencies, MultiParamTypeClasses, TypeFamilies, ScopedTypeVariables #-}
module Gargantext.Utils.Jobs.Monad (
  -- * Types and classes
    JobEnv(..)
  , NumRunners
  , JobError(..)

  , MonadJob(..)

  -- * Reporting errors to users in a friendly way
  , ToHumanFriendlyError(..)

  -- * Tracking jobs status
  , MonadJobStatus(..)

  -- * Functions
  , newJobEnv
  , defaultJobSettings
  , genSecret
  , getJobsSettings
  , getJobsState
  , getJobsMap
  , getJobsQueue
  , queueJob
  , findJob
  , checkJID
  , withJob
  , handleIDError
  , removeJob
  , markFailedNoErr
  , markFailureNoErr
  ) where

import Gargantext.Utils.Jobs.Error
import Gargantext.Utils.Jobs.Map
import Gargantext.Utils.Jobs.Queue
import Gargantext.Utils.Jobs.Settings
import Gargantext.Utils.Jobs.State

import Control.Concurrent.STM
import Control.Exception
import Control.Monad.Except
import Control.Monad.Reader
import Data.Kind (Type)
import Data.Map.Strict (Map)
import Data.Time.Clock
import Data.Void (Void)
import qualified Data.Text as T
import Network.HTTP.Client (Manager)
import Prelude

import qualified Servant.Job.Core as SJ
import qualified Servant.Job.Types as SJ
import Data.Proxy

data JobEnv t w a = JobEnv
  { jeSettings :: JobSettings
  , jeState    :: JobsState t w a
  , jeManager  :: Manager
  }

newJobEnv
  :: (EnumBounded t, Monoid w)
  => JobSettings
  -> Map t Prio
  -> Manager
  -> IO (JobEnv t w a)
newJobEnv js prios mgr = JobEnv js <$> newJobsState js prios <*> pure mgr

type NumRunners = Int

defaultJobSettings :: NumRunners -> SJ.SecretKey -> JobSettings
defaultJobSettings numRunners k = JobSettings
  { jsNumRunners = numRunners
  , jsJobTimeout = 30 * 60 -- 30 minutes
  , jsIDTimeout  = 30 * 60 -- 30 minutes
  , jsGcPeriod   =  1 * 60 -- 1 minute
  , jsSecretKey  = k
  , jsDebugLogs  = False
  }

genSecret :: IO SJ.SecretKey
genSecret = SJ.generateSecretKey

class MonadIO m => MonadJob m t w a | m -> t w a where
  getJobEnv :: m (JobEnv t w a)

instance MonadIO m => MonadJob (ReaderT (JobEnv t w a) m) t w a where
  getJobEnv = ask

getJobsSettings :: MonadJob m t w a => m JobSettings
getJobsSettings = jeSettings <$> getJobEnv

getJobsState :: MonadJob m t w a => m (JobsState t w a)
getJobsState = jeState <$> getJobEnv

getJobsMap :: MonadJob m t w a => m (JobMap (SJ.JobID 'SJ.Safe) w a)
getJobsMap = jobsData <$> getJobsState

getJobsQueue :: MonadJob m t w a => m (Queue t (SJ.JobID 'SJ.Safe))
getJobsQueue = jobsQ <$> getJobsState

queueJob
  :: (MonadJob m t w a, Ord t)
  => t
  -> i
  -> (SJ.JobID 'SJ.Safe -> i -> Logger w -> IO a)
  -> m (SJ.JobID 'SJ.Safe)
queueJob jobkind input f = do
  js <- getJobsSettings
  st <- getJobsState
  liftIO (pushJob jobkind input f js st)

findJob
  :: MonadJob m t w a
  => SJ.JobID 'SJ.Safe
  -> m (Maybe (JobEntry (SJ.JobID 'SJ.Safe) w a))
findJob jid = do
  jmap <- getJobsMap
  liftIO $ lookupJob jid jmap

data JobError
  =
  -- | We expected to find a job tagged internall as \"job\", but we found the input @T.Text@ instead.
    InvalidIDType T.Text
  -- | The given ID expired.
  | IDExpired Int
  | InvalidMacID T.Text
  | UnknownJob Int
  | JobException SomeException
  deriving Show

checkJID
  :: MonadJob m t w a
  => SJ.JobID 'SJ.Unsafe
  -> m (Either JobError (SJ.JobID 'SJ.Safe))
checkJID (SJ.PrivateID tn n t d) = do
  now <- liftIO getCurrentTime
  js <- getJobsSettings
  if | tn /= "job" -> pure (Left $ InvalidIDType $ T.pack tn)
     | now > addUTCTime (fromIntegral $ jsIDTimeout js) t -> pure (Left $ IDExpired n)
     | d /= SJ.macID tn (jsSecretKey js) t n -> pure (Left $ InvalidMacID $ T.pack d)
     | otherwise -> pure $ Right (SJ.PrivateID tn n t d)

withJob
  :: MonadJob m t w a
  => SJ.JobID 'SJ.Unsafe
  -> (SJ.JobID 'SJ.Safe -> JobEntry (SJ.JobID 'SJ.Safe) w a -> m r)
  -> m (Either JobError (Maybe r))
withJob jid f = do
  r <- checkJID jid
  case r of
    Left e -> pure (Left e)
    Right jid' -> do
      mj <- findJob jid'
      case mj of
        Nothing -> pure (Right Nothing)
        Just j  -> Right . Just <$> f jid' j

handleIDError
  :: MonadError e m
  => (JobError -> e)
  -> m (Either JobError a)
  -> m a
handleIDError toE act = act >>= \r -> case r of
  Left err -> throwError (toE err)
  Right a  -> pure a

removeJob
  :: (Ord t, MonadJob m t w a)
  => Bool -- is it queued (and we have to remove jid from queue)
  -> t
  -> SJ.JobID 'SJ.Safe
  -> m ()
removeJob queued t jid = do
  q <- getJobsQueue
  m <- getJobsMap
  liftIO . atomically $ do
    when queued $
      deleteQueue t jid q
    deleteJob jid m

--
-- Tracking jobs status
--

-- | A monad to query for the status of a particular job /and/ submit updates for in-progress jobs.
class MonadJobStatus m where

  -- | This is type family for the concrete 'JobHandle' that is associated to
  -- a job when it starts and it can be used to query for its completion status. Different environment
  -- can decide how this will look like.
  type JobHandle      m :: Type

  type JobType        m :: Type
  type JobOutputType  m :: Type
  type JobEventType   m :: Type

  -- | A job handle that doesn't do anything. Sometimes useful in all those circumstances
  -- where we need to test a function taking a 'JobHandle' as input but we are not interested
  -- in the progress tracking.
  noJobHandle :: Proxy m -> JobHandle m

  -- | Retrevies the latest 'JobEventType' from the underlying monad. It can be
  -- used to query the latest status for a particular job, given its 'JobHandle' as input.
  getLatestJobStatus :: JobHandle m -> m (JobEventType m)

  -- | Adds an extra \"tracer\" that logs events to the passed action. Produces
  -- a new 'JobHandle'.
  withTracer :: Logger (JobEventType m) -> JobHandle m -> (JobHandle m -> m a) -> m a

  -- Creating events

  -- | Start tracking a new 'JobEventType' with 'n' remaining steps.
  markStarted :: Int -> JobHandle m -> m ()

  -- | Mark 'n' steps of the job as succeeded, while simultaneously substracting this number
  -- from the remaining steps.
  markProgress :: Int -> JobHandle m -> m ()

  -- | Mark 'n' step of the job as failed, while simultaneously substracting this number
  -- from the remaining steps. Attach an optional error message to the failure.
  markFailure :: forall e. ToHumanFriendlyError e => Int -> Maybe e -> JobHandle m -> m ()

  -- | Finish tracking a job by marking all the remaining steps as succeeded.
  markComplete :: JobHandle m -> m ()

  -- | Finish tracking a job by marking all the remaining steps as failed. Attach an optional
  -- message to the failure.
  markFailed :: forall e. ToHumanFriendlyError e => Maybe e -> JobHandle m -> m ()

  -- | Add 'n' more steps to the running computation, they will be marked as remaining.
  addMoreSteps :: MonadJobStatus m => Int -> JobHandle m -> m ()

-- | Helper on top of 'markFailed' for when we don't have a diagnostic to log.
markFailedNoErr :: MonadJobStatus m => JobHandle m -> m ()
markFailedNoErr = markFailed (Nothing :: Maybe Void)

markFailureNoErr :: MonadJobStatus m => Int -> JobHandle m -> m ()
markFailureNoErr steps = markFailure steps (Nothing :: Maybe Void)
