{-# LANGUAGE DeriveDataTypeable #-}

{-# LANGUAGE DeriveDataTypeable, ScopedTypeVariables #-}

type NDT = NominalDiffTime

sumLogIntervals :: [LogInterval] -> Rational
sumLogIntervals ivals = F.foldl' (+) (fromInteger 0) $ fmap (toRational . ilen . workInterval) ivals

{-|
  The depreciation function should return a value between 0 and 1;
  this result is multiplied by the length of an interval of work to determine
  the depreciated value of the work.
-}
newtype Depreciation = Depreciation { depf :: NDT -> Rational } 

payouts :: WorkIndex -> Payouts
payouts widx = let addIntervalDiff total ivals = (\dt -> (dt + total, dt)) $ sumLogIntervals ivals 
                   (totalTime, keyTimes) = M.mapAccum addIntervalDiff (fromInteger 0) $ M.map snd widx
               in M.map (\kt -> kt / totalTime) keyTimes

{-|
  Payouts are determined by computing a depreciated duration value for
  each work interval. This function computes the percentage of the total
  work allocated to each address.
-}
payouts :: Depreciation -> UTCTime -> WorkIndex -> Payouts
payouts dep ptime widx = let addIntervalDiff :: (Functor f, Foldable f) => NDT -> f LogInterval -> (NDT, NDT)
                             addIntervalDiff total ivals = (\dt -> (dt + total, dt)) $ sumLogIntervals dep ptime ivals 
                             (totalTime, keyTimes) = M.mapAccum addIntervalDiff (fromInteger 0) $ M.map snd widx
                         in M.map (\kt -> toRational $ kt / totalTime) keyTimes
{-|
  
-}
sumLogIntervals :: (Functor f, Foldable f) => Depreciation -> UTCTime -> f LogInterval -> NDT
sumLogIntervals dep ptime ivals = F.foldl' (+) (fromInteger 0) $ fmap (depreciateInterval dep ptime) ivals

depreciateInterval :: Depreciation -> UTCTime -> LogInterval -> NDT
depreciateInterval dep ptime ival = let depreciation :: Rational
                                        depreciation = depf dep $ diffUTCTime ptime (end . workInterval $ ival)
                                    in  fromRational $ depreciation * (toRational . ilen . workInterval $ ival)