{-
SBV: SMT Based Verification in Haskell

Copyright (c) 2010-2025, Levent Erkok (erkokl@gmail.com)
All rights reserved.

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    * Redistributions in binary form must reproduce the above copyright
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      documentation and/or other materials provided with the distribution.
    * Neither the name of the developer (Levent Erkok) nor the
      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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-}

module ShowTDiff where

import Data.List (intercalate)
import Data.Ratio
import Data.Time.Clock
import GHC.Real (Ratio((:%)))
import Numeric (showFFloat)

-- | Show 'NominalDiffTime' in human readable form. 'NominalDiffTime' is
-- essentially picoseconds (10^-12 seconds). We show it so that
-- it's represented at the day:hour:minute:second.XXX granularity.
showTDiff :: NominalDiffTime -> String
showTDiff diff
   | denom /= 1    -- Should never happen! But just in case.
   = show diff
   | True
   = intercalate ":" fields
   where total, denom :: Integer
         total :% denom = (picoFactor % 1) * toRational diff

         -- there are 10^12 pico-seconds in a second
         picoFactor :: Integer
         picoFactor = (10 :: Integer) ^ (12 :: Integer)

         (s2p, m2s, h2m, d2h) = case drop 1 $ scanl (*) 1 [picoFactor, 60, 60, 24] of
                                  (s2pv : m2sv : h2mv : d2hv : _) -> (s2pv, m2sv, h2mv, d2hv)
                                  _                               -> (0, 0, 0, 0)  -- won't ever happen

         (days,    days')    = total    `divMod` d2h
         (hours,   hours')   = days'    `divMod` h2m
         (minutes, seconds') = hours'   `divMod` m2s
         (seconds, picos)    = seconds' `divMod` s2p
         secondsPicos        =  show seconds
                             ++ dropWhile (/= '.') (showFFloat (Just 3) (fromIntegral picos * (10**(-12) :: Double)) "s")

         aboveSeconds = map (\(t, v) -> show v ++ [t]) $ dropWhile (\p -> snd p == 0) [('d', days), ('h', hours), ('m', minutes)]
         fields       = aboveSeconds ++ [secondsPicos]