module Nuthatch.Runtime
  ( retryStartup
  ) where

import           Control.Exception (SomeException)
import           Control.Retry
  ( RetryStatus (..)
  , constantDelay
  , limitRetries
  , retrying
  )
import           Data.Aeson (Value (String), toJSON)
import           Data.Either (isLeft)
import           Data.Text (Text)
import qualified Data.Text as T
import           Nuthatch.Audit (audit)
import           Nuthatch.Recovery (trySynchronous)

retryStartup :: Int -> Int -> Text -> IO value -> IO value
retryStartup attempts delayMs dependency action = do
  result <- retrying policy shouldRetry $ \_ ->
    tryStartup action
  case result of
    Right value -> pure value
    Left _ -> do
      audit "dependency_startup" "exhausted" Nothing
        [ ("dependency", String dependency)
        , ("attempts", toJSON attempts)
        ]
      fail ("startup dependency unavailable: " <> T.unpack dependency)
  where
    policy =
      limitRetries (max 0 (attempts - 1))
        <> constantDelay (max 1 delayMs * 1000)
    shouldRetry status outcome = do
      if isLeft outcome
        then audit "dependency_startup" "retry" Nothing
          [ ("dependency", String dependency)
          , ("attempt", toJSON (rsIterNumber status + 1))
          ]
        else pure ()
      pure (isLeft outcome)

tryStartup :: IO value -> IO (Either SomeException value)
tryStartup = trySynchronous