Add noise to sleep duration

1 files changed, 12 insertions, 0 deletions

diff --git a/src/lib/haskell/Utils/Time.hs b/src/lib/haskell/Utils/Time.hs
index 88aeeb6..ce36293 100644
--- a/src/lib/haskell/Utils/Time.hs
+++ b/src/lib/haskell/Utils/Time.hs
@@ -1,6 +1,7 @@
 module Utils.Time
   ( getCurrentFormattedTime
   , asleepDuration
+  , addNoise
   ) where
 
 import           Data.Text           (Text)
@@ -9,6 +10,7 @@ import           Data.Time.Clock     (DiffTime)
 import qualified Data.Time.Clock     as Clock
 import qualified Data.Time.Format    as Format
 import qualified Data.Time.LocalTime as LocalTime
+import qualified System.Random       as Random
 
 getCurrentFormattedTime :: IO Text
 getCurrentFormattedTime = do
@@ -27,3 +29,13 @@ asleepDuration from to t =
     Nothing
   where
     day = (realToFrac Clock.nominalDay) :: DiffTime
+
+-- |Add noise to a duration.
+-- > t - (n / 2) <= addNoise t n <= t + (n / 2)
+addNoise :: DiffTime -> DiffTime -> IO DiffTime
+addNoise t n = do
+  r <- Random.randomIO :: IO Float
+  return $ t + (Clock.secondsToDiffTime . round $ (r * (fromIntegral . toSeconds $ n))) - n / 2
+
+  where
+    toSeconds dt = Clock.diffTimeToPicoseconds dt `div` 10^(12 :: Integer)