lib/Data/Time/LocalTime/Internal/TimeOfDay.hs

    {-# OPTIONS -fno-warn-unused-imports #-}
    #include "HsConfigure.h"
    -- #hide
    module Data.Time.LocalTime.Internal.TimeOfDay
    (
        -- * Time of day
        TimeOfDay(..),midnight,midday,makeTimeOfDayValid,
        utcToLocalTimeOfDay,localToUTCTimeOfDay,
        timeToTimeOfDay,timeOfDayToTime,
        dayFractionToTimeOfDay,timeOfDayToDayFraction
    ) where

    import Control.DeepSeq
    import Data.Typeable
    import Data.Fixed
    #if LANGUAGE_Rank2Types
    import Data.Data
    #endif
    import Data.Time.Clock.Internal.DiffTime
    import Data.Time.Calendar.Private
    import Data.Time.LocalTime.Internal.TimeZone

    -- | Time of day as represented in hour, minute and second (with picoseconds), typically used to express local time of day.
    data TimeOfDay = TimeOfDay {
        -- | range 0 - 23
        todHour    :: Int,
        -- | range 0 - 59
        todMin     :: Int,
        -- | Note that 0 <= 'todSec' < 61, accomodating leap seconds.
        -- Any local minute may have a leap second, since leap seconds happen in all zones simultaneously
        todSec     :: Pico
    } deriving (Eq,Ord
    #if LANGUAGE_DeriveDataTypeable
    #if LANGUAGE_Rank2Types
    #if HAS_DataPico
        ,Data, Typeable
    #endif
    #endif
    #endif
        )

    instance NFData TimeOfDay where
        rnf (TimeOfDay h m s) = rnf h `seq` rnf m `seq` s `seq` () -- FIXME: Data.Fixed had no NFData instances yet at time of writing

    -- | Hour zero
    midnight :: TimeOfDay
    midnight = TimeOfDay 0 0 0

    -- | Hour twelve
    midday :: TimeOfDay
    midday = TimeOfDay 12 0 0

    instance Show TimeOfDay where
        show (TimeOfDay h m s) = (show2 h) ++ ":" ++ (show2 m) ++ ":" ++ (show2Fixed s)

    makeTimeOfDayValid :: Int -> Int -> Pico -> Maybe TimeOfDay
    makeTimeOfDayValid h m s = do
        _ <- clipValid 0 23 h
        _ <- clipValid 0 59 m
        _ <- clipValid 0 60.999999999999 s
        return (TimeOfDay h m s)

    -- | Convert a time of day in UTC to a time of day in some timezone, together with a day adjustment.
    utcToLocalTimeOfDay :: TimeZone -> TimeOfDay -> (Integer,TimeOfDay)
    utcToLocalTimeOfDay zone (TimeOfDay h m s) = (fromIntegral (div h' 24),TimeOfDay (mod h' 24) (mod m' 60) s) where
        m' = m + timeZoneMinutes zone
        h' = h + (div m' 60)

    -- | Convert a time of day in some timezone to a time of day in UTC, together with a day adjustment.
    localToUTCTimeOfDay :: TimeZone -> TimeOfDay -> (Integer,TimeOfDay)
    localToUTCTimeOfDay zone = utcToLocalTimeOfDay (minutesToTimeZone (negate (timeZoneMinutes zone)))

    posixDayLength :: DiffTime
    posixDayLength = fromInteger 86400

    -- | Get the time of day given a time since midnight.
    -- Time more than 24h will be converted to leap-seconds.
    timeToTimeOfDay :: DiffTime -> TimeOfDay
    timeToTimeOfDay dt | dt >= posixDayLength = TimeOfDay 23 59 (60 + (realToFrac (dt - posixDayLength)))
    timeToTimeOfDay dt = TimeOfDay (fromInteger h) (fromInteger m) s where
        s' = realToFrac dt
        s = mod' s' 60
        m' = div' s' 60
        m = mod' m' 60
        h = div' m' 60

    -- | Get the time since midnight for a given time of day.
    timeOfDayToTime :: TimeOfDay -> DiffTime
    timeOfDayToTime (TimeOfDay h m s) = ((fromIntegral h) * 60 + (fromIntegral m)) * 60 + (realToFrac s)

    -- | Get the time of day given the fraction of a day since midnight.
    dayFractionToTimeOfDay :: Rational -> TimeOfDay
    dayFractionToTimeOfDay df = timeToTimeOfDay (realToFrac (df * 86400))

    -- | Get the fraction of a day since midnight given a time of day.
    timeOfDayToDayFraction :: TimeOfDay -> Rational
    timeOfDayToDayFraction tod = realToFrac (timeOfDayToTime tod) / realToFrac posixDayLength