{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards   #-}
module Database.PostgreSQL.Simple.QueueSpec (spec, main) where
import           Control.Concurrent
import           Control.Concurrent.Async
import           Control.Monad
import           Data.Aeson
import           Data.Function
import           Data.IORef
import           Data.List
import           Database.PostgreSQL.Simple.Queue
import           Database.PostgreSQL.Simple.Queue.Migrate
import           Test.Hspec                     (Spec, hspec, it)
import           Test.Hspec.Expectations.Lifted
import           Test.Hspec.DB

main :: IO ()
main = hspec spec

spec :: Spec
spec = describeDB migrate "Database.Queue" $ do
  itDB "empty locks nothing" $
    tryLockDB `shouldReturn` Nothing

  itDB "empty gives count 0" $
    getCountDB `shouldReturn` 0

  itDB "enqueues/tryLocks/unlocks" $ do
    payloadId <- enqueueDB $ String "Hello"
    getCountDB `shouldReturn` 1

    Just Payload {..} <- tryLockDB
    getCountDB `shouldReturn` 0

    pId `shouldBe` payloadId
    pValue `shouldBe` String "Hello"
    tryLockDB `shouldReturn` Nothing

    unlockDB pId
    getCountDB `shouldReturn` 1

  itDB "tryLocks/dequeues" $ do
    Just Payload {..} <- tryLockDB
    getCountDB `shouldReturn` 0

    dequeueDB pId `shouldReturn` ()
    tryLockDB `shouldReturn` Nothing

  it "enqueues and dequeues concurrently tryLock" $ \testDB -> do
    let withPool' = withPool testDB
        elementCount = 1000 :: Int
        expected = [0 .. elementCount - 1]

    ref <- newIORef []

    loopThreads <- replicateM 10 $ async $ fix $ \next -> do
      mpayload <- withPool' tryLock
      case mpayload of
        Nothing -> next
        Just Payload {..}  -> do
          lastCount <- atomicModifyIORef ref
                     $ \xs -> (pValue : xs, length xs + 1)
          withPool' $ flip dequeue pId
          when (lastCount < elementCount) next

    -- Fork a hundred threads and enqueue an index
    forM_ [0 .. elementCount - 1] $ \i ->
      forkIO $ void $ withPool' $ flip enqueue $ toJSON i

    waitAnyCancel loopThreads
    Just decoded <- mapM (decode . encode) <$> readIORef ref
    sort decoded `shouldBe` sort expected

  it "enqueues and dequeues concurrently lock" $ \testDB -> do
    let withPool' = withPool testDB
        elementCount = 1000 :: Int
        expected = [0 .. elementCount - 1]

    ref <- newIORef []

    loopThreads <- replicateM 10 $ async $ fix $ \next -> do
      Payload {..} <- withPool' lock
      lastCount <- atomicModifyIORef ref
                 $ \xs -> (pValue : xs, length xs + 1)
      withPool' $ flip dequeue pId
      when (lastCount < elementCount) next

    -- Fork a hundred threads and enqueue an index
    forM_ [0 .. elementCount - 1] $ \i -> forkIO $ void $ withPool' $
      flip enqueue $ toJSON i

    waitAnyCancel loopThreads
    Just decoded <- mapM (decode . encode) <$> readIORef ref
    sort decoded `shouldBe` sort expected