Server.Ingest: new handling of unassigned trackers

now takes all potential stops along each trip into account when guessing
tickets; also checks if a ticket is still likely in case the tracker
switched its direction. This should solve many cases where a tracker is
accidentally turned off or falls asleep halfway before the last station
of one trip, then wakes up in the middle of the next.

5 files changed, 170 insertions, 88 deletions

diff --git a/lib/API.hs b/lib/API.hs
index b2635c1..7ebfb06 100644
--- a/lib/API.hs
+++ b/lib/API.hs
@@ -1,10 +1,11 @@
 {-# LANGUAGE DataKinds            #-}
+{-# LANGUAGE DeriveAnyClass       #-}
 {-# LANGUAGE ExplicitNamespaces   #-}
 {-# LANGUAGE UndecidableInstances #-}
 
 -- | The sole authorative definition of this server's API, given as a Servant-style
 -- Haskell type. All other descriptions of the API are generated from this one.
-module API (API, CompleteAPI, GtfsRealtimeAPI, RegisterJson(..), Metrics(..)) where
+module API (API, CompleteAPI, GtfsRealtimeAPI, RegisterJson(..), Metrics(..), SentPing(..)) where
 
 import           Data.Map                    (Map)
 import           Data.Proxy                  (Proxy (..))
@@ -51,12 +52,22 @@ import           Prometheus
 import           Proto.GtfsRealtime          (FeedMessage)
 import           Servant.API.ContentTypes    (Accept (..))
 
+-- | a bare ping as sent by a tracker device
+data SentPing = SentPing
+  { sentPingToken     :: TrackerId
+  , sentPingGeopos    :: Geopos
+  , sentPingTimestamp :: UTCTime
+  } deriving (Generic)
+
+instance FromJSON SentPing where
+  parseJSON = genericParseJSON (aesonOptions "sentPing")
+
 -- | tracktrain's API
 type API =
   -- ingress API (put this behind BasicAuth?)
   -- TODO: perhaps require a first ping for registration?
        "tracker" :> "register" :> ReqBody '[JSON] RegisterJson :> Post '[JSON] Token
-  :<|> "tracker" :> "ping" :> ReqBody '[JSON] TrainPing :> Post '[JSON] (Maybe TrainAnchor)
+  :<|> "tracker" :> "ping" :> ReqBody '[JSON] SentPing :> Post '[JSON] (Maybe TrainAnchor)
   :<|> "tracker" :> "ping" :> "ws" :> WebSocket
   :<|> "ticket" :> "subscribe" :> Capture "Ticket Id" UUID :> WebSocket
   :<|> "debug" :> "pings" :> Get '[JSON] (Map Token [TrainPing])
@@ -94,6 +105,8 @@ instance ToSchema RegisterJson where
 instance ToSchema Value where
   declareNamedSchema _ = pure $ NamedSchema (Just "json") $ mempty
       & type_ ?~ SwaggerObject
+instance ToSchema SentPing where
+  declareNamedSchema = genericDeclareNamedSchema (GTFS.swaggerOptions "trainPing")
 
 
 
@@ -124,3 +137,4 @@ instance Message msg => MimeRender Proto msg where
 instance {-# OVERLAPPABLE #-} Message msg => ToSchema msg where
   declareNamedSchema proxy =
     pure (NamedSchema (Just (messageName proxy)) mempty)
+
diff --git a/lib/Extrapolation.hs b/lib/Extrapolation.hs
index 389d047..759b31e 100644
--- a/lib/Extrapolation.hs
+++ b/lib/Extrapolation.hs
@@ -18,6 +18,7 @@ import qualified Data.Vector                         as V
 import           GHC.Float                           (int2Double)
 import           GHC.IO                              (unsafePerformIO)
 
+import           API                                 (SentPing (..))
 import           Conduit                             (MonadIO (liftIO))
 import           Data.List                           (sortBy, sortOn)
 import           Data.Ord                            (Down (..))
@@ -29,8 +30,7 @@ import           Persist                             (Geopos (..),
                                                       Station (..), Stop (..),
                                                       Ticket (..), TicketId,
                                                       Token (..), Tracker (..),
-                                                      TrainAnchor (..),
-                                                      TrainPing (..))
+                                                      TrainAnchor (..))
 import           Server.Util                         (utcToSeconds)
 
 -- | Determines how to extrapolate delays (and potentially other things) from the real-time
@@ -44,7 +44,7 @@ class Extrapolator strategy where
     -> Ticket
     -> V.Vector (Stop, Station, TimeZoneSeries)
     -> V.Vector ShapePoint
-    -> TrainPing
+    -> SentPing
     -> TrainAnchor
 
   -- | extrapolate status at some time (i.e. "how much delay does the train have *now*?")
@@ -65,14 +65,14 @@ instance Extrapolator LinearExtrapolator where
   -- (in case the train just stands still for a while, take the most recent update)
   extrapolateAtPosition _ history positionNow =
     fmap (minimumBy (compare `on` difference))
-    $ NE.nonEmpty $ sortOn (Down . trainAnchorWhen)
+    $ NE.nonEmpty $ sortOn (Down . trainAnchorCreated)
     $ NE.filter (\a -> trainAnchorSequence a < positionNow) history
     where difference status = positionNow - trainAnchorSequence status
 
-  extrapolateAnchorFromPing _ ticketId Ticket{..} stops shape ping@TrainPing{..} = TrainAnchor
-    { trainAnchorCreated = trainPingTimestamp
+  extrapolateAnchorFromPing _ ticketId Ticket{..} stops shape ping@SentPing{..} = TrainAnchor
+    { trainAnchorCreated = sentPingTimestamp
     , trainAnchorTicket = ticketId
-    , trainAnchorWhen = utcToSeconds trainPingTimestamp ticketDay
+    , trainAnchorWhen = utcToSeconds sentPingTimestamp ticketDay
     , trainAnchorSequence
     , trainAnchorDelay
     , trainAnchorMsg = Nothing
@@ -81,8 +81,8 @@ instance Extrapolator LinearExtrapolator where
           (trainAnchorDelay, trainAnchorSequence) = linearDelay stops shape ping ticketDay
           tzseries = undefined
 
-linearDelay :: V.Vector (Stop, Station, TimeZoneSeries) -> V.Vector ShapePoint -> TrainPing -> Day -> (Seconds, Double)
-linearDelay tripStops shape TrainPing{..} runningDay = (observedDelay, observedSequence)
+linearDelay :: V.Vector (Stop, Station, TimeZoneSeries) -> V.Vector ShapePoint -> SentPing -> Day -> (Seconds, Double)
+linearDelay tripStops shape SentPing{..} runningDay = (observedDelay, observedSequence)
   where -- at which (fractional) sequence number is the ping?
         observedSequence = int2Double (stopSequence lastStop)
           + observedProgress * int2Double (stopSequence nextStop - stopSequence lastStop)
@@ -93,7 +93,7 @@ linearDelay tripStops shape TrainPing{..} runningDay = (observedDelay, observedS
           + if expectedProgress == 1
           -- if the hypothetical on-time train is already at (or past) the next station,
           -- just add the time distance we're behind
-          then seconds2Double (utcToSeconds trainPingTimestamp runningDay - nextSeconds)
+          then seconds2Double (utcToSeconds sentPingTimestamp runningDay - nextSeconds)
           -- otherwise the above is sufficient
           else 0
 
@@ -107,14 +107,14 @@ linearDelay tripStops shape TrainPing{..} runningDay = (observedDelay, observedS
           | p < 0     -> 0
           | p > 1     -> 1
           | otherwise -> p
-          where p = seconds2Double (utcToSeconds trainPingTimestamp runningDay - lastSeconds)
+          where p = seconds2Double (utcToSeconds sentPingTimestamp runningDay - lastSeconds)
                   / seconds2Double expectedTravelTime
 
         -- scheduled duration between last and next stops
         expectedTravelTime = nextSeconds - lastSeconds
 
         -- closest point on the shape; this is where we assume the train to be
-        closestPoint = minimumBy (compare `on` euclid trainPingGeopos) line
+        closestPoint = minimumBy (compare `on` euclid sentPingGeopos) line
 
         -- scheduled departure at last & arrival at next stop
         lastSeconds = toSeconds (stopDeparture lastStop) lastTzSeries runningDay
diff --git a/lib/Persist.hs b/lib/Persist.hs
index 46e5ef4..e268455 100644
--- a/lib/Persist.hs
+++ b/lib/Persist.hs
@@ -142,6 +142,8 @@ TrainPing json sql=tt_trip_ping
   token TrackerId
   geopos Geopos
   timestamp UTCTime
+  sequence Double
+  ticket TicketId
   deriving Show Generic Eq
 
 -- status of a train somewhen in time (may be in the future),
@@ -177,6 +179,8 @@ instance ToSchema TrainAnchor where
 instance ToSchema Announcement where
   declareNamedSchema = genericDeclareNamedSchema (GTFS.swaggerOptions "announcement")
 
+type InSql a = ReaderT SqlBackend (LoggingT (ResourceT IO)) a
+
 runSqlWithoutLog :: MonadIO m
   => Pool SqlBackend
   -> ReaderT SqlBackend (NoLoggingT (ResourceT IO)) a
@@ -188,7 +192,7 @@ runSqlWithoutLog pool = liftIO . flip runSqlPersistMPool pool
 -- no better way than to nest logger monads …
 runSql :: (MonadLogger m, MonadIO m, MonadReader LoggingConfig m)
   => Pool SqlBackend
-  -> ReaderT SqlBackend (LoggingT (ResourceT IO)) a
+  -> InSql  a
   -> m a
 runSql pool x = do
   conf <- ask
diff --git a/lib/Server/Ingest.hs b/lib/Server/Ingest.hs
index d774017..6a8383f 100644
--- a/lib/Server/Ingest.hs
+++ b/lib/Server/Ingest.hs
@@ -3,12 +3,15 @@
 
 module Server.Ingest (handleTrackerRegister, handleTrainPing, handleWS) where
 import           API                                 (Metrics (..),
-                                                      RegisterJson (..))
+                                                      RegisterJson (..),
+                                                      SentPing (..))
 import           Control.Concurrent.STM              (atomically, readTVar,
                                                       writeTQueue)
-import           Control.Monad                       (forever, void, when)
+import           Control.Monad                       (forM, forever, unless,
+                                                      void, when)
 import           Control.Monad.Catch                 (handle)
-import           Control.Monad.Extra                 (ifM, mapMaybeM, whenJust)
+import           Control.Monad.Extra                 (ifM, mapMaybeM, whenJust,
+                                                      whenJustM)
 import           Control.Monad.IO.Class              (MonadIO (liftIO))
 import           Control.Monad.Logger                (LoggingT, logInfoN,
                                                       logWarnN)
@@ -23,6 +26,7 @@ import           Data.Text                           (Text)
 import           Data.Text.Encoding                  (decodeASCII, decodeUtf8)
 import           Data.Time                           (NominalDiffTime,
                                                       UTCTime (..), addUTCTime,
+                                                      diffUTCTime,
                                                       getCurrentTime,
                                                       nominalDay)
 import qualified Data.Vector                         as V
@@ -38,10 +42,12 @@ import           Server.Util                         (ServiceM, getTzseries,
                                                       utcToSeconds)
 
 import           Config                              (LoggingConfig,
-                                                      ServerConfig)
+                                                      ServerConfig (..))
+import           Control.Exception                   (throw)
+import           Control.Monad.Logger.CallStack      (logErrorN)
 import           Data.ByteString                     (ByteString)
 import           Data.ByteString.Lazy                (toStrict)
-import           Data.Foldable                       (minimumBy)
+import           Data.Foldable                       (find, minimumBy)
 import           Data.Function                       (on, (&))
 import qualified Data.Text                           as T
 import           Data.Time.LocalTime.TimeZone.Series (TimeZoneSeries)
@@ -49,12 +55,12 @@ import qualified Data.UUID                           as UUID
 import           Extrapolation                       (Extrapolator (..),
                                                       LinearExtrapolator (..),
                                                       euclid)
+import           GHC.Generics                        (Generic)
 import           GTFS                                (seconds2Double)
 import           Prometheus                          (decGauge, incGauge)
 import           Server.Base                         (ServerState)
 
 
-
 handleTrackerRegister
   :: Pool SqlBackend
   -> RegisterJson
@@ -74,78 +80,96 @@ handleTrainPing
   -> ServerState
   -> ServerConfig
   -> LoggingT (ReaderT LoggingConfig Handler) a
-  -> TrainPing
+  -> SentPing
   -> LoggingT (ReaderT LoggingConfig Handler) (Maybe TrainAnchor)
-handleTrainPing dbpool subscribers cfg onError ping@TrainPing{..} =
-  isTokenValid dbpool trainPingToken >>= \case
+handleTrainPing dbpool subscribers cfg onError ping@SentPing{..} =
+  isTokenValid dbpool sentPingToken >>= \case
   Nothing -> onError >> pure Nothing
   Just tracker@Tracker{..} -> do
 
-    -- if the tracker is not associated with a ticket, it is probably
-    -- just starting out on a new trip, or has finished an old one.
-    maybeTicketId <- case trackerCurrentTicket of
-      Just ticketId -> pure (Just ticketId)
-      Nothing -> runSql dbpool $ do
-        now <- liftIO getCurrentTime
-        tickets <- selectList [ TicketDay ==. utctDay now, TicketCompleted ==. False ] []
-        ticketsWithFirstStation <- flip mapMaybeM tickets
-            (\ticket@(Entity ticketId _) -> do
-              selectFirst [StopTicket ==. ticketId] [Asc StopSequence] >>= \case
-                Nothing -> pure Nothing
-                Just (Entity _ stop) -> do
-                  station <- getJust (stopStation stop)
-                  tzseries <- liftIO $ getTzseries cfg (GTFS.tzname (stopDeparture stop))
-                  pure (Just (ticket, station, stop, tzseries)))
-
-        if null ticketsWithFirstStation then pure Nothing else do
-          let (closestTicket, _, _, _) = minimumBy
-                -- (compare `on` euclid trainPingGeopos . stationGeopos . snd)
-                (compare `on`
-                 (\(Entity _ ticket, station, stop, tzseries) ->
-                     let
-                       runningDay = ticketDay ticket
-                       spaceDistance = euclid trainPingGeopos (stationGeopos station)
-                       timeDiff =
-                         GTFS.toSeconds (stopDeparture stop) tzseries runningDay
-                         - utcToSeconds now runningDay
-                     in
-                       euclid trainPingGeopos (stationGeopos station)
-                       + abs (seconds2Double timeDiff / 3600)))
-                ticketsWithFirstStation
-          logInfoN
-            $ "Tracker "+|UUID.toString (coerce trainPingToken)|+
-            " is now handling ticket "+|UUID.toString (coerce (entityKey closestTicket))|+
-            " (trip "+|ticketTripName (entityVal closestTicket)|+")."
-
-          update trainPingToken
-            [TrackerCurrentTicket =. Just (entityKey closestTicket)]
-
-          pure (Just (entityKey closestTicket))
-
-    ticketId <- case maybeTicketId of
+    unless (serverConfigDebugMode cfg) $ do
+      now <- liftIO getCurrentTime
+      let timeDiff = sentPingTimestamp `diffUTCTime` now
+      when (utctDay sentPingTimestamp /= utctDay now) $ do
+        logErrorN "received ping for wrong day"
+        throw err400
+      when (timeDiff < 10) $ do
+        logWarnN "received ping more than 10 seconds out of date"
+        throw err400
+      when (timeDiff > 10) $ do
+        logWarnN "received ping from more than 10 seconds in the future"
+        throw err400
+
+    ticketId <- case trackerCurrentTicket of
       Just ticketId -> pure ticketId
-      Nothing -> do
-        logWarnN $ "Tracker "+|UUID.toString (coerce trainPingToken)|+
-          " sent a ping, but no trips are running today."
-        throwError err400
+      -- if the tracker is not associated with a ticket, it is probably new
+      -- & should be auto-associated with the most fitting current ticket
+      Nothing -> runSql dbpool (guessTicketFromPing cfg ping) >>= \case
+        Just ticketId -> pure ticketId
+        Nothing -> do
+          logWarnN $ "Tracker "+|UUID.toString (coerce sentPingToken)|+
+            " sent a ping, but no trips are running today."
+          throwError err400
+
+
+    runSql dbpool $ insertSentPing subscribers cfg ping tracker ticketId
+
+insertSentPing
+  :: ServerState
+  -> ServerConfig
+  -> SentPing
+  -> Tracker
+  -> TicketId
+  -> InSql (Maybe TrainAnchor)
+insertSentPing subscribers cfg ping@SentPing{..} tracker@Tracker{..} ticketId = do
+  ticket@Ticket{..} <- getJust ticketId
+
+  stations <- selectList [ StopTicket ==. ticketId ] [Asc StopArrival]
+     >>= mapM (\stop -> do
+       station <- getJust (stopStation (entityVal stop))
+       tzseries <- liftIO $ getTzseries cfg (GTFS.tzname (stopArrival (entityVal stop)))
+       pure (entityVal stop, station, tzseries))
+     <&> V.fromList
+
+  shapePoints <- selectList [ShapePointShape ==. ticketShape] [Asc ShapePointIndex]
+    <&> (V.fromList . fmap entityVal)
+
+
+  let anchor = extrapolateAnchorFromPing LinearExtrapolator
+                  ticketId ticket stations shapePoints ping
 
-    runSql dbpool $ do
-      ticket@Ticket{..} <- getJust ticketId
 
-      stations <- selectList [ StopTicket ==. ticketId ] [Asc StopArrival]
-         >>= mapM (\stop -> do
-           station <- getJust (stopStation (entityVal stop))
-           tzseries <- liftIO $ getTzseries cfg (GTFS.tzname (stopArrival (entityVal stop)))
-           pure (entityVal stop, station, tzseries))
-         <&> V.fromList
+  maybeReassign <- selectFirst
+      [ TrainPingTicket ==. ticketId ]
+      [ Desc TrainPingTimestamp ]
+    <&> find (\ping -> trainPingSequence (entityVal ping) > trainAnchorSequence anchor)
+    >> guessTicketFromPing cfg ping
+    <&> find (/= ticketId)
 
-      shapePoints <- selectList [ShapePointShape ==. ticketShape] [Asc ShapePointIndex]
-        <&> (V.fromList . fmap entityVal)
 
-      let anchor = extrapolateAnchorFromPing LinearExtrapolator
-                      ticketId ticket stations shapePoints ping
+      -- mapM (\newTicketId -> if ticketId /= newTicketId then Just newTicketId else Nothing))
+    -- >>= (\ping -> guessTicketFromPing cfg ping >>= \case
+    --   Just newTicketId | ticketId /= newTicketId -> pure (Just newTicketId)
+    --   _ -> pure Nothing)
 
-      insert ping
+  case maybeReassign of
+    Just newTicketId -> do
+      update sentPingToken
+        [TrackerCurrentTicket =. Just newTicketId ]
+      logInfoN $ "tracker "+|UUID.toText (coerce sentPingToken)|+
+        "has switched direction, and was reassigned to ticket "
+        +|UUID.toText (coerce newTicketId)|+"."
+      insertSentPing subscribers cfg ping tracker newTicketId
+    Nothing -> do
+      let trackedPing = TrainPing
+           { trainPingToken = sentPingToken
+           , trainPingGeopos = sentPingGeopos
+           , trainPingTimestamp = sentPingTimestamp
+           , trainPingSequence = trainAnchorSequence anchor
+           , trainPingTicket = ticketId
+           }
+
+      insert trackedPing
 
       last <- selectFirst [TrainAnchorTicket ==. ticketId] [Desc TrainAnchorWhen]
       -- only insert new estimates if they've actually changed anything
@@ -158,18 +182,18 @@ handleTrainPing dbpool subscribers cfg onError ping@TrainPing{..} =
             & (\(stop, _, _) -> stopSequence stop)
             & fromIntegral
       when (trainAnchorSequence anchor + 0.1 >= maxSequence) $ do
-        update trainPingToken
+        update sentPingToken
           [TrackerCurrentTicket =. Nothing]
         update ticketId
           [TicketCompleted =. True]
-        logInfoN $ "Tracker "+|UUID.toString (coerce trainPingToken)|+
+        logInfoN $ "Tracker "+|UUID.toString (coerce sentPingToken)|+
           " has completed ticket "+|UUID.toString (coerce ticketId)|+
           " (trip "+|ticketTripName|+")"
 
       queues <- liftIO $ atomically $ do
         queues <- readTVar subscribers <&> M.lookup (coerce ticketId)
         whenJust queues $
-          mapM_ (\q -> writeTQueue q (Just ping))
+          mapM_ (\q -> writeTQueue q (Just trackedPing))
         pure queues
       pure (Just anchor)
 
@@ -196,6 +220,46 @@ handleWS dbpool subscribers cfg Metrics{..} conn = do
           Just anchor -> liftIO $ WS.sendTextData conn (A.encode anchor)
           Nothing     -> pure ()
 
+
+guessTicketFromPing :: ServerConfig -> SentPing -> InSql (Maybe (Key Ticket))
+guessTicketFromPing cfg SentPing{..} = do
+  tickets <- selectList [ TicketDay ==. utctDay sentPingTimestamp, TicketCompleted ==. False ] []
+
+  ticketsWithStation <- forM tickets (\ticket@(Entity ticketId _) -> do
+    stops <- selectList [StopTicket ==. ticketId] [Asc StopSequence] >>= mapM (\(Entity _ stop) -> do
+      station <- getJust (stopStation stop)
+      tzseries <- liftIO $ getTzseries cfg (GTFS.tzname (stopDeparture stop))
+      pure (station, stop, tzseries))
+    pure (ticket, stops))
+
+  if null ticketsWithStation then pure Nothing else do
+    let (closestTicket, _) = ticketsWithStation
+         & minimumBy (compare `on` (\(Entity _ ticket, stations) ->
+            let
+              runningDay = ticketDay ticket
+              smallestDistance = stations
+                <&> (\(station, stop, tzseries) -> spaceAndTimeDiff
+                      (sentPingGeopos, utcToSeconds sentPingTimestamp runningDay)
+                      (stationGeopos station, GTFS.toSeconds (stopDeparture stop) tzseries runningDay))
+                & minimum
+            in smallestDistance))
+
+    logInfoN
+      $ "Tracker "+|UUID.toString (coerce sentPingToken)|+
+      " is now handling ticket "+|UUID.toString (coerce (entityKey closestTicket))|+
+      " (trip "+|ticketTripName (entityVal closestTicket)|+")."
+
+    update sentPingToken
+      [TrackerCurrentTicket =. Just (entityKey closestTicket)]
+
+    pure (Just (entityKey closestTicket))
+
+spaceAndTimeDiff :: (Geopos, GTFS.Seconds) -> (Geopos, GTFS.Seconds) -> Double
+spaceAndTimeDiff (pos1, time1) (pos2, time2) =
+  spaceDistance + abs (seconds2Double timeDiff / 3600)
+  where spaceDistance = euclid pos1 pos2
+        timeDiff = time1 - time2
+
 -- TODO: proper debug logging for expired tokens
 isTokenValid :: Pool SqlBackend -> TrackerId -> ServiceM (Maybe Tracker)
 isTokenValid dbpool token = runSql dbpool $ get token >>= \case
diff --git a/todo.org b/todo.org
index 1148ba6..396c343 100644
--- a/todo.org
+++ b/todo.org
@@ -4,8 +4,6 @@
 ** TODO auto-reconnect of /tracker websocket fails after android has gone to sleep
 ** DONE /tracker should remember its token, not constantly open a new one
 either via a cookie or url parameter & redirect
-** TODO matching of tokens to trip ought not to assume trips are at their start position
-this produces horrible results if the tracker is started towards a trip's end
 ** TODO train anchors are sorted wrong
 probably based on sequence number, not based on time. results in "stuck"
 nonsensical delay information if we had a mistaken geolocation in the middle
@@ -18,6 +16,8 @@ that time, since we assume linear movement.
 ** DONE do not give tripupdates after tickets are completed or outdated
 ** TODO tickets are not reliably marked completed
 ** TODO any kind of check against unrealistically fast travel?
+** DONE matching of tokens to trip ought not to assume trips are at their start position
+this produces horrible results if the tracker is started towards a trip's end
 * TODO implement GTFS realtime
 ** TODO get google to accept trip updates
 ** DONE get google to accept service alerts