{-# LANGUAGE OverloadedStrings #-}

module SubscriptionStoreSpec (spec) where

import           Control.Concurrent
import           Control.Concurrent.STM
import           Control.Exception
import           Control.Monad
import           Data.IORef
import           Subscription.Store
import           Subscription.Types
import           Test.Hspec
import           Types.Msg

spec :: Spec
spec = do
  describe "global pending delivery limits" $ do
    it "shares the message limit across subscriptions and coalesces notification" $ do
      slowEvents <- newIORef (0 :: Int)
      firstOverflow <- newIORef (0 :: Int)
      secondOverflow <- newIORef (0 :: Int)
      store <-
        newSubscriptionStore
          (PendingLimits 1 1024)
          (modifyIORef' slowEvents (+ 1))
      registerSubscription store "1" "A" (modifyIORef' firstOverflow (+ 1))
      registerSubscription store "2" "B" (modifyIORef' secondOverflow (+ 1))

      dispatchMessage store (message "1" "one")
        `shouldReturn` DispatchQueued
      dispatchMessage store (message "2" "two")
        `shouldReturn` DispatchDropped True
      dispatchMessage store (message "2" "three")
        `shouldReturn` DispatchDropped False

      readIORef slowEvents `shouldReturn` 0
      readIORef firstOverflow `shouldReturn` 0
      readIORef secondOverflow `shouldReturn` 2

    it "rejects a delivery that exceeds the global byte limit" $ do
      store <- newSubscriptionStore (PendingLimits 10 4) (pure ())
      registerSubscription store "1" "A" (pure ())

      dispatchMessage store (message "1" "12345")
        `shouldReturn` DispatchDropped True

    it "re-enables notification after the backlog recovers" $ do
      slowEvents <- newIORef (0 :: Int)
      callbackStarted <- newEmptyMVar
      releaseCallback <- newEmptyMVar
      stopping <- newTVarIO False
      store <-
        newSubscriptionStore
          (PendingLimits 1 1024)
          (modifyIORef' slowEvents (+ 1))
      register
        store
        "1"
        (SubscriptionMeta "A" Nothing False)
        (SubscribeConfig Nothing Nothing)
        (\_ -> putMVar callbackStarted () >> takeMVar releaseCallback)
        (pure ())
      startWorkers
        1
        store
        (readTVar stopping >>= check)
        (const (pure ()))

      dispatchMessage store (message "1" "one")
        `shouldReturn` DispatchQueued
      takeMVar callbackStarted
      dispatchMessage store (message "1" "two")
        `shouldReturn` DispatchDropped True
      putMVar releaseCallback ()
      atomically (awaitCallbackDrain store)
      readIORef slowEvents `shouldReturn` 1

      dispatchMessage store (message "1" "three")
        `shouldReturn` DispatchQueued
      takeMVar callbackStarted
      dispatchMessage store (message "1" "four")
        `shouldReturn` DispatchDropped True
      putMVar releaseCallback ()
      atomically (awaitCallbackDrain store)
      readIORef slowEvents `shouldReturn` 2
      atomically (writeTVar stopping True)

    it "releases capacity when a callback throws" $ do
      callbackFailed <- newEmptyMVar
      stopping <- newTVarIO False
      store <- newSubscriptionStore (PendingLimits 1 1024) (pure ())
      register
        store
        "1"
        (SubscriptionMeta "A" Nothing False)
        (SubscribeConfig Nothing Nothing)
        (const (throwIO (userError "callback failed")))
        (pure ())
      startWorkers
        1
        store
        (readTVar stopping >>= check)
        (putMVar callbackFailed)

      dispatchMessage store (message "1" "one")
        `shouldReturn` DispatchQueued
      void (takeMVar callbackFailed)
      atomically (awaitCallbackDrain store)
      dispatchMessage store (message "1" "two")
        `shouldReturn` DispatchQueued
      void (takeMVar callbackFailed)
      atomically (awaitCallbackDrain store)
      atomically (writeTVar stopping True)

    it "removes a one-shot subscription whose delivery is dropped" $ do
      store <- newSubscriptionStore (PendingLimits 1 1024) (pure ())
      registerSubscription store "1" "A" (pure ())
      register
        store
        "2"
        (SubscriptionMeta "B" Nothing True)
        (SubscribeConfig Nothing Nothing)
        (const (pure ()))
        (pure ())

      dispatchMessage store (message "1" "one")
        `shouldReturn` DispatchQueued
      dispatchMessage store (message "2" "two")
        `shouldReturn` DispatchDropped True
      dispatchMessage store (message "2" "two")
        `shouldReturn` DispatchMissing

registerSubscription
  :: SubscriptionStore
  -> SID
  -> Subject
  -> IO ()
  -> IO ()
registerSubscription store sidValue subjectValue =
  register
    store
    sidValue
    (SubscriptionMeta subjectValue Nothing False)
    (SubscribeConfig Nothing Nothing)
    (const (pure ()))

message :: SID -> Payload -> Msg
message sidValue payloadValue =
  Msg "A" sidValue Nothing (Just payloadValue) Nothing