Many improvements

[Rakka.git] / Rakka / W3CDateTime.hs

diff --git a/Rakka/W3CDateTime.hs b/Rakka/W3CDateTime.hs
new file mode 100644 (file)
index 0000000..85af47a
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+++ b/Rakka/W3CDateTime.hs
@@ -0,0 +1,99 @@
+module Rakka.W3CDateTime
+    ( formatW3CDateTime
+    , parseW3CDateTime
+    )
+    where
+
+import           Control.Monad
+import           Data.Time
+import           Prelude hiding (min)
+import           Text.ParserCombinators.Parsec
+import           Text.Printf
+
+
+formatW3CDateTime :: ZonedTime -> String
+formatW3CDateTime zonedTime
+    = formatLocalTime (zonedTimeToLocalTime zonedTime)
+      ++
+      formatTimeZone (zonedTimeZone zonedTime)
+    where
+      formatLocalTime :: LocalTime -> String
+      formatLocalTime localTime
+          = let (year, month, day) = toGregorian (localDay localTime)
+                timeOfDay          = localTimeOfDay localTime
+                (secInt, secFrac)  = properFraction (todSec timeOfDay)
+            in
+              (printf "%04d-%02d-%02dT%02d:%02d:%02d"
+                      year
+                      month
+                      day
+                      (todHour timeOfDay)
+                      (todMin timeOfDay)
+                      (secInt :: Int))
+              ++
+              (if secFrac == 0
+               then ""
+               else tail (show secFrac))
+      
+      formatTimeZone :: TimeZone -> String
+      formatTimeZone tz
+          = case timeZoneMinutes tz of
+              offset | offset <  0 -> '-':(showTZ $ negate offset)
+                     | offset == 0 -> "Z"
+                     | otherwise   -> '+':(showTZ offset)
+      
+      showTZ :: Int -> String   
+      showTZ offset
+          = let hour   = offset `div` 60
+                minute = offset - hour * 60
+            in 
+              show2 hour ++ ":" ++ show2 minute
+            
+      show2 :: Int -> String
+      show2 n | n < 10    = '0':(show n)
+              | otherwise = show n
+
+
+parseW3CDateTime :: String -> Maybe ZonedTime
+parseW3CDateTime src
+    = case parse w3cDateTime "" src of
+        Right zt -> Just zt
+        Left  _  -> Nothing
+
+w3cDateTime :: Parser ZonedTime
+w3cDateTime = do year <- liftM read (count 4 digit)
+                 mon  <- option 1 (char '-' >> liftM read (count 2 digit))
+                 day  <- option 1 (char '-' >> liftM read (count 2 digit))
+                 (hour, min, sec, offMin)
+                     <- option (0, 0, 0, 0) time
+                 eof
+
+                 let julianDay = fromGregorian year mon day
+                     timeOfDay = TimeOfDay hour min (fromRational $ toRational sec)
+                     localTime = LocalTime julianDay timeOfDay
+                     timeZone  = minutesToTimeZone offMin
+                     zonedTime = ZonedTime localTime timeZone
+
+                 return zonedTime
+    where
+      time :: Parser (Int, Int, Double, Int)
+      time = do char 'T'
+                hour   <- liftM read (count 2 digit)
+                char ':'
+                min    <- liftM read (count 2 digit)
+                sec    <- option 0 $ do char ':'
+                                        secInt  <- count 2 digit
+                                        secFrac <- option "" $ do c  <- char '.'
+                                                                  cs <- many1 digit
+                                                                  return (c:cs)
+                                        return $ read (secInt ++ secFrac)
+                offMin <- (char 'Z' >> return 0)
+                        <|>
+                        (do sign <- (char '+' >> return 1)
+                                    <|>
+                                    (char '-' >> return (-1))
+                            h    <- liftM read (count 2 digit)
+                            char ':'
+                            m    <- liftM read (count 2 digit)
+                            return $ sign * h * 60 + m)
+                return (hour, min, sec, offMin)
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