import Control.Applicative
import Control.Monad
import Control.Exception.Base

import qualified Data.Aeson.Types as A

import qualified Data.Text as T

import qualified Data.Aeson.Types as A
import qualified Data.Text as T

import Control.Applicative
import Control.Monad
import Control.Exception.Base

  in M.map (\kt -> toRational $ kt / totalTime) keyTimes

  in  M.map (\kt -> toRational $ kt / totalTime) keyTimes

  in M.map (bimap (fmap event) (fmap workInterval)) $ logSum

  in  M.map (bimap (fmap event) (fmap workInterval)) $ logSum

  in insert (btcAddr entry) acc workIndex

  in  insert (btcAddr entry) acc workIndex

newtype Months = Months Integer 
monthsLength :: Months -> NominalDiffTime
monthsLength (Months i) = fromInteger $ 60 * 60 * 24 * 30 * i
linearDepreciation :: Months -> Months -> Depreciation
linearDepreciation undepPeriod depPeriod = 
  let maxDepreciable :: NominalDiffTime
      maxDepreciable = monthsLength undepPeriod + monthsLength depPeriod 

      zeroTime :: NominalDiffTime
      zeroTime = fromInteger 0

  let depf ndt = undefined

  in Depreciation depf
-- data LogEventParseError = LogEventParseError String deriving (Show, Typeable)
-- instance Exception LogEventParseError where
-- instance FromField WorkEvent where
--   fromField f m = let fromText "start_work" = return StartWork
--                       fromText "stop_work"  = return StopWork
--                       fromText a = conversionError $ LogEventParseError $ "unrecognized log event type " ++ a
--                   in fromField f m >>= fromText
-- instance FromRow LogEntry where
--   fromRow = LogEntry <$> field <*> field <*> field 

      depf :: NominalDiffTime -> Rational
      depf dt = if dt < monthsLength undepPeriod 
        then 1
        else toRational (max zeroTime (maxDepreciable - dt)) / toRational maxDepreciable

      zeroTime :: NominalDiffTime
      zeroTime = fromInteger 0

      depf :: NominalDiffTime -> Rational
      depf dt = if dt < monthsLength undepPeriod 
        then 1
        else toRational (max zeroTime (maxDepreciable - dt)) / toRational maxDepreciable
  in Depreciation depf