{-# LANGUAGE NoMonomorphismRestriction, OverloadedStrings #-}
module EZCouch.Retry where

import Prelude ()
import ClassyPrelude
import Control.Concurrent
import EZCouch.Logging


retryingEither [] action = action 
retryingEither (i:is) action = action >>= processResult
  where 
    processResult (Left _) 
      | i == 0 = retryingEither is action
      | otherwise = liftIO (threadDelay i) >> retryingEither is action
    processResult r = return r

retryingEither' = retryingEither defaultIntervals

retrying exceptionIntervals action = retrying_ 0
  where
    retrying_ attempt = catch action processException
      where
        exceptionInterval = listToMaybe . drop attempt . exceptionIntervals
        processException e 
          | Just i <- exceptionInterval e = do
              logLn 2 
                $ "Error occurred: " ++ show e ++ ". " 
                ++ "Retrying with a " ++ show (i `div` sec) ++ "s delay."
              unless (i == 0) (liftIO (threadDelay i)) 
              retrying_ (attempt + 1)
          | otherwise = throwIO e

defaultIntervals = [sec, sec * 5, sec * 15]
sec = 10 ^ 6