    {-# OPTIONS -Wall -Werror #-}

    module Data.Time.Format
    	(
    	-- * UNIX-style formatting
    	module Data.Time.Format,
    	module Data.Time.Format.Parse
    	) where

    import Data.Time.Format.Parse
    import Data.Time.LocalTime
    import Data.Time.Calendar.WeekDate
    import Data.Time.Calendar.OrdinalDate
    import Data.Time.Calendar
    import Data.Time.Calendar.Private
    import Data.Time.Clock
    import Data.Time.Clock.POSIX

    import System.Locale
    import Data.Maybe
    import Data.Char
    import Data.Fixed

    -- <http://www.opengroup.org/onlinepubs/007908799/xsh/strftime.html>
    class FormatTime t where
    	formatCharacter :: Char -> Maybe (TimeLocale -> t -> String)

    -- | Substitute various time-related information for each %-code in the string, as per 'formatCharacter'.
    --
    -- For all types (note these three are done here, not by 'formatCharacter'):
    --
    -- [@%%@] @%@
    --
    -- [@%t@] tab
    --
    -- [@%n@] newline
    --
    -- For TimeZone (and ZonedTime and UTCTime):
    --
    -- [@%z@] timezone offset on the format @-HHMM@.
    --
    -- [@%Z@] timezone name
    --
    -- For LocalTime (and ZonedTime and UTCTime):
    --
    -- [@%c@] as 'dateTimeFmt' @locale@ (e.g. @%a %b %e %H:%M:%S %Z %Y@)
    --
    -- For TimeOfDay (and LocalTime and ZonedTime and UTCTime):
    --
    -- [@%R@] same as @%H:%M@
    --
    -- [@%T@] same as @%H:%M:%S@
    --
    -- [@%X@] as 'timeFmt' @locale@ (e.g. @%H:%M:%S@)
    --
    -- [@%r@] as 'time12Fmt' @locale@ (e.g. @%I:%M:%S %p@)
    --
    -- [@%P@] day half from ('amPm' @locale@), converted to lowercase, @am@, @pm@
    --
    -- [@%p@] day half from ('amPm' @locale@), @AM@, @PM@
    --
    -- [@%H@] hour, 24-hour, leading 0 as needed, @00@ - @23@
    --
    -- [@%I@] hour, 12-hour, leading 0 as needed, @01@ - @12@
    --
    -- [@%k@] hour, 24-hour, leading space as needed, @ 0@ - @23@
    --
    -- [@%l@] hour, 12-hour, leading space as needed, @ 1@ - @12@
    --
    -- [@%M@] minute, @00@ - @59@
    --
    -- [@%S@] second, without decimal part, @00@ - @60@
    --
    -- [@%q@] picosecond, including trailing zeros, @000000000000@ - @999999999999@.
    --
    -- [@%Q@] decimal point and up to 12 second decimals, without trailing zeros.
    -- For a whole number of seconds, @%Q@ produces the empty string.
    --
    -- For UTCTime and ZonedTime:
    --
    -- [@%s@] number of whole seconds since the Unix epoch. For times before
    -- the Unix epoch, this is a negative number. Note that in @%s.%q@ and @%s%Q@
    -- the decimals are positive, not negative. For example, 0.9 seconds
    -- before the Unix epoch is formatted as @-1.1@ with @%s%Q@.
    --
    -- For Day (and LocalTime and ZonedTime and UTCTime):
    --
    -- [@%D@] same as @%m\/%d\/%y@
    --
    -- [@%F@] same as @%Y-%m-%d@
    --
    -- [@%x@] as 'dateFmt' @locale@ (e.g. @%m\/%d\/%y@)
    --
    -- [@%Y@] year
    --
    -- [@%y@] last two digits of year, @00@ - @99@
    --
    -- [@%C@] century (being the first two digits of the year), @00@ - @99@
    --
    -- [@%B@] month name, long form ('fst' from 'months' @locale@), @January@ - @December@
    --
    -- [@%b@, @%h@] month name, short form ('snd' from 'months' @locale@), @Jan@ - @Dec@
    --
    -- [@%m@] month of year, leading 0 as needed, @01@ - @12@
    --
    -- [@%d@] day of month, leading 0 as needed, @01@ - @31@
    --
    -- [@%e@] day of month, leading space as needed,  @ 1@ - @31@
    --
    -- [@%j@] day of year for Ordinal Date format, @001@ - @366@
    --
    -- [@%G@] year for Week Date format
    --
    -- [@%g@] last two digits of year for Week Date format, @00@ - @99@
    --
    -- [@%f@] century (first two digits of year) for Week Date format, @00@ - @99@
    --
    -- [@%V@] week for Week Date format, @01@ - @53@
    --
    -- [@%u@] day for Week Date format, @1@ - @7@
    --
    -- [@%a@] day of week, short form ('snd' from 'wDays' @locale@), @Sun@ - @Sat@
    --
    -- [@%A@] day of week, long form ('fst' from 'wDays' @locale@), @Sunday@ - @Saturday@
    --
    -- [@%U@] week number of year, where weeks start on Sunday (as 'sundayStartWeek'), @00@ - @53@
    --
    -- [@%w@] day of week number, @0@ (= Sunday) - @6@ (= Saturday)
    --
    -- [@%W@] week number of year, where weeks start on Monday (as 'mondayStartWeek'), @00@ - @53@
    formatTime :: (FormatTime t) => TimeLocale -> String -> t -> String
    formatTime _ [] _ = ""
    formatTime locale ('%':c:cs) t = (formatChar c) ++ (formatTime locale cs t) where
    	formatChar '%' = "%"
    	formatChar 't' = "\t"
    	formatChar 'n' = "\n"
    	formatChar _ = case (formatCharacter c) of
    		Just f -> f locale t
    		_ -> ""
    formatTime locale (c:cs) t = c:(formatTime locale cs t)

    instance FormatTime LocalTime where
    	formatCharacter 'c' = Just (\locale -> formatTime locale (dateTimeFmt locale))
    	formatCharacter c = case (formatCharacter c) of
    		Just f -> Just (\locale dt -> f locale (localDay dt))
    		Nothing -> case (formatCharacter c) of
    			Just f -> Just (\locale dt -> f locale (localTimeOfDay dt))
    			Nothing -> Nothing

    instance FormatTime TimeOfDay where
    	-- Aggregate
    	formatCharacter 'R' = Just (\locale -> formatTime locale "%H:%M")
    	formatCharacter 'T' = Just (\locale -> formatTime locale "%H:%M:%S")
    	formatCharacter 'X' = Just (\locale -> formatTime locale (timeFmt locale))
    	formatCharacter 'r' = Just (\locale -> formatTime locale (time12Fmt locale))
    	-- AM/PM
    	formatCharacter 'P' = Just (\locale day -> map toLower ((if (todHour day) < 12 then fst else snd) (amPm locale)))
    	formatCharacter 'p' = Just (\locale day -> (if (todHour day) < 12 then fst else snd) (amPm locale))
    	-- Hour
    	formatCharacter 'H' = Just (\_ -> show2 . todHour)
    	formatCharacter 'I' = Just (\_ -> show2 . (\h -> (mod (h - 1) 12) + 1) . todHour)
    	formatCharacter 'k' = Just (\_ -> show2Space . todHour)
    	formatCharacter 'l' = Just (\_ -> show2Space . (\h -> (mod (h - 1) 12) + 1) . todHour)
    	-- Minute
    	formatCharacter 'M' = Just (\_ -> show2 . todMin)
    	-- Second
    	formatCharacter 'S' = Just (\_ -> (show2 :: Int -> String) . truncate . todSec)
    	formatCharacter 'q' = Just (\_ -> drop 1 . dropWhile (/='.') . showFixed False . todSec)
    	formatCharacter 'Q' = Just (\_ -> dropWhile (/='.') . showFixed True . todSec)

    	-- Default
    	formatCharacter _   = Nothing

    instance FormatTime ZonedTime where
    	formatCharacter 'c' = Just (\locale -> formatTime locale (dateTimeFmt locale))
    	formatCharacter 's' = Just (\_ zt -> show (floor (utcTimeToPOSIXSeconds (zonedTimeToUTC zt)) :: Integer))
    	formatCharacter c = case (formatCharacter c) of
    		Just f -> Just (\locale dt -> f locale (zonedTimeToLocalTime dt))
    		Nothing -> case (formatCharacter c) of
    			Just f -> Just (\locale dt -> f locale (zonedTimeZone dt))
    			Nothing -> Nothing

    instance FormatTime TimeZone where
    	formatCharacter 'z' = Just (\_ -> timeZoneOffsetString)
    	formatCharacter 'Z' =
                Just (\_ z -> let n = timeZoneName z
                               in if null n then timeZoneOffsetString z else n)
    	formatCharacter _ = Nothing

    instance FormatTime Day where
    	-- Aggregate
    	formatCharacter 'D' = Just (\locale -> formatTime locale "%m/%d/%y")
    	formatCharacter 'F' = Just (\locale -> formatTime locale "%Y-%m-%d")
    	formatCharacter 'x' = Just (\locale -> formatTime locale (dateFmt locale))

    	-- Year Count
    	formatCharacter 'Y' = Just (\_ -> show . fst . toOrdinalDate)
    	formatCharacter 'y' = Just (\_ -> show2 . mod100 . fst . toOrdinalDate)
    	formatCharacter 'C' = Just (\_ -> show2 . div100 . fst . toOrdinalDate)
    	-- Month of Year
    	formatCharacter 'B' = Just (\locale -> fst . (\(_,m,_) -> (months locale) !! (m - 1)) . toGregorian)
    	formatCharacter 'b' = Just (\locale -> snd . (\(_,m,_) -> (months locale) !! (m - 1)) . toGregorian)
    	formatCharacter 'h' = Just (\locale -> snd . (\(_,m,_) -> (months locale) !! (m - 1)) . toGregorian)
    	formatCharacter 'm' = Just (\_ -> show2 . (\(_,m,_) -> m) . toGregorian)
    	-- Day of Month
    	formatCharacter 'd' = Just (\_ -> show2 . (\(_,_,d) -> d) . toGregorian)
    	formatCharacter 'e' = Just (\_ -> show2Space . (\(_,_,d) -> d) . toGregorian)
    	-- Day of Year
    	formatCharacter 'j' = Just (\_ -> show3 . snd . toOrdinalDate)

    	-- ISO 8601 Week Date
    	formatCharacter 'G' = Just (\_ -> show . (\(y,_,_) -> y) . toWeekDate)
    	formatCharacter 'g' = Just (\_ -> show2 . mod100 . (\(y,_,_) -> y) . toWeekDate)
    	formatCharacter 'f' = Just (\_ -> show2 . div100 . (\(y,_,_) -> y) . toWeekDate)

    	formatCharacter 'V' = Just (\_ -> show2 . (\(_,w,_) -> w) . toWeekDate)
    	formatCharacter 'u' = Just (\_ -> show . (\(_,_,d) -> d) . toWeekDate)

    	-- Day of week
    	formatCharacter 'a' = Just (\locale -> snd . ((wDays locale) !!) . snd . sundayStartWeek)
    	formatCharacter 'A' = Just (\locale -> fst . ((wDays locale) !!) . snd . sundayStartWeek)
    	formatCharacter 'U' = Just (\_ -> show2 . fst . sundayStartWeek)
    	formatCharacter 'w' = Just (\_ -> show . snd . sundayStartWeek)
    	formatCharacter 'W' = Just (\_ -> show2 . fst . mondayStartWeek)

    	-- Default
    	formatCharacter _   = Nothing

    instance FormatTime UTCTime where
    	formatCharacter c = fmap (\f locale t -> f locale (utcToZonedTime utc t)) (formatCharacter c)