darcs-beta-2.7.98.1: src/DateMatcher.hs
-- Copyright (C) 2004 David Roundy
--
-- This program is free software; you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation; either version 2, or (at your option)
-- any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program; see the file COPYING. If not, write to
-- the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
-- Boston, MA 02110-1301, USA.
{-# LANGUAGE ExistentialQuantification #-}
module DateMatcher ( parseDateMatcher
-- for debugging only
, DateMatcher(..), getMatchers ) where
import Prelude hiding ( catch )
import Control.Exception.Extensible ( catch, throw )
import System.IO.Error ( isUserError, ioeGetErrorString )
import Data.Maybe ( isJust )
import System.Time
import IsoDate ( parseDate, englishDateTime, englishInterval, englishLast, iso8601Interval,
resetCalendar, subtractFromMCal, getLocalTz,
MCalendarTime(..), toMCalendarTime, unsafeToCalendarTime,
unsetTime,
)
import Text.ParserCombinators.Parsec ( eof, parse, ParseError )
-- | 'withinDay' @x y@ is true if @x <= y < (x + one_day)@
-- Note that this converts the two dates to @ClockTime@ to avoid
-- any timezone-related errors
withinDay :: CalendarTime -> CalendarTime -> Bool
withinDay a b = within (Just $ toClockTime a)
(Just (addToClockTime day $ toClockTime a))
(toClockTime b)
where day = TimeDiff 0 0 1 0 0 0 0
-- | 'dateRange' @x1 x2 y@ is true if @x1 <= y < x2@
-- Since @x1@ and @x2@ can be underspecified, we simply assume the
-- first date that they could stand for.
dateRange :: Maybe MCalendarTime -> Maybe MCalendarTime -> CalendarTime -> Bool
dateRange a b c = cDateRange (fmap unsafeToCalendarTime a)
(fmap unsafeToCalendarTime b) c
-- | 'cDateRange' @x1 x2 y@ is true if @x1 <= y < x2@
cDateRange :: Maybe CalendarTime -> Maybe CalendarTime -> CalendarTime -> Bool
cDateRange a b c = within (fmap toClockTime a)
(fmap toClockTime b) (toClockTime c)
-- | 'within' @x1 x2 y@ is true if @x1 <= y < x2@
within :: Maybe ClockTime -> Maybe ClockTime -> ClockTime -> Bool
within (Just start) (Just end) time = start <= time && time < end
within Nothing (Just end) time = time < end
within (Just start) Nothing time = start <= time
within _ _ _ = undefined
-- | 'samePartialDate' @range exact@ is true if @exact@ falls
-- within the a range of dates represented by @range@.
-- The purpose of this function is to support matching on partially
-- specified dates. That is, if you only specify the date 2007,
-- this function should match any dates within that year. On the
-- other hand, if you specify 2007-01, this function will match any
-- dates within that month. This function only matches up to the
-- second.
samePartialDate :: MCalendarTime -> CalendarTime -> Bool
samePartialDate a b_ =
within (Just clockA)
(Just $ addToClockTime interval clockA)
(toClockTime calB)
where interval
| isJust (mctSec a) = second
| isJust (mctMin a) = minute
| isJust (mctHour a) = hour
| isJust (mctYDay a) = day
| mctWeek a = maybe week (const day) (mctWDay a)
| isJust (mctDay a) = day
| isJust (mctMonth a) = month
| otherwise = year
year = TimeDiff 1 0 0 0 0 0 0
month = TimeDiff 0 1 0 0 0 0 0
week = TimeDiff 0 0 7 0 0 0 0
day = TimeDiff 0 0 1 0 0 0 0
hour = TimeDiff 0 0 0 1 0 0 0
minute = TimeDiff 0 0 0 0 1 0 0
second = TimeDiff 0 0 0 0 0 1 0
--
clockA = toClockTime $ unsafeToCalendarTime a
calB = resetCalendar b_
-- | A 'DateMatcher' combines a potential parse for a date string
-- with a "matcher" function that operates on a given date.
-- We use an existential type on the matcher to allow
-- the date string to either be interpreted as a point in time
-- or as an interval.
data DateMatcher = forall d . (Show d) =>
DM String -- name
(Either ParseError d) -- parser
(d -> CalendarTime -> Bool) -- matcher
-- | 'parseDateMatcher' @s@ return the first matcher in
-- 'getMatchers' that can parse 's'
parseDateMatcher :: String -> IO (CalendarTime -> Bool)
parseDateMatcher d =
do matcher <- tryMatchers `fmap` getMatchers d
-- Hack: test the matcher against the current date and discard the results.
-- We just want to make sure it won't throw any exceptions when we use it for real.
matcher `fmap` now >>= (`seq` return matcher)
`catchUserError`
-- If the user enters a date > maxint seconds ago, the toClockTime
-- function cannot work.
\e -> if e == "Time.toClockTime: invalid input"
then error "Can't handle dates that far back!"
else error e
where
catchUserError comp handler
= catch comp (\e -> if isUserError e then handler (ioeGetErrorString e) else throw e)
-- | 'getMatchers' @d@ returns the list of matchers that will be
-- applied on @d@. If you wish to extend the date parsing code,
-- this will likely be the function that you modify to do so.
getMatchers :: String -> IO [DateMatcher]
getMatchers d =
do rightNow <- now
let midnightToday = unsetTime rightNow
mRightNow = toMCalendarTime rightNow
matchIsoInterval (Left dur) = dateRange (Just $ dur `subtractFromMCal` mRightNow) (Just mRightNow)
matchIsoInterval (Right (a,b)) = dateRange (Just a) (Just b)
tzNow <- getLocalTz
return -- note that the order of these is quite important as some matchers
-- can match the same date.
[ DM "from English date"
(parseDateWith $ englishLast midnightToday)
(\(a,_) -> cDateRange (Just a) Nothing)
, DM "specific English date"
(parseDateWith $ englishDateTime midnightToday)
withinDay
, DM "English interval"
(parseDateWith $ englishInterval rightNow)
(uncurry cDateRange)
, DM "ISO 8601 interval"
(parseDateWith $ iso8601Interval tzNow)
matchIsoInterval
, DM "CVS, ISO 8601, or old style date"
(parseDate tzNow d)
samePartialDate ]
where
tillEof p = do { x <- p; eof; return x }
parseDateWith p = parse (tillEof p) "" d
-- | 'tryMatchers' @ms@ returns the first successful match in @ms@
-- It is an error if there are no matches
tryMatchers :: [DateMatcher] -> (CalendarTime -> Bool)
tryMatchers (DM _ parsed matcher : ms) =
case parsed of
Left _ -> tryMatchers ms
Right d -> matcher d
tryMatchers [] = error "Can't support fancy dates."
-- darcs-doc: self-explanatory
now :: IO CalendarTime
now = getClockTime >>= toCalendarTime