src/Mail.hs

   1 -- |Email functions and data types.
   2
   3 module Mail
   4 where
   5
   6 import Control.Concurrent
   7 import Control.Concurrent.MVar
   8 import Control.Exception (evaluate)
   9 import Data.List (intercalate)
  10 import System.Exit
  11 import System.Process
  12 import System.Time (CalendarTime(..), ClockTime, getClockTime, Month, toCalendarTime)
  13 import System.IO
  14
  15 type Header = String
  16
  17 -- |A crude model of an RFC821 email message.
  18 data Message = Message { headers :: [Header],
  19                          subject :: String,
  20                          body    :: String,
  21                          from    :: String,
  22                          to      :: String }
  23              deriving (Eq)
  24
  25 -- |Showing a message will print it in roughly RFC-compliant
  26 -- form. This form is sufficient for handing the message off to
  27 -- sendmail.
  28 instance Show Message where
  29     show m =
  30         concat [ if (length (headers m) == 0) then "" else (intercalate "\n" (headers m)) ++ "\n",
  31                  "Subject: " ++ (subject m) ++ "\n",
  32                  "From: " ++ (from m) ++ "\n",
  33                  "To: " ++ (to m) ++ "\n",
  34                  "\n",
  35                  (body m) ]
  36
  37
  38
  39 -- |Pad a string on the left with zeros until the entire string has
  40 -- length n.
  41 pad_left :: String -> Int -> String
  42 pad_left str n
  43          | n < (length str) = str
  44          | otherwise = (replicate num_zeros '0') ++ str
  45     where num_zeros = n - (length str)
  46
  47
  48
  49 -- |Formats a month name according to RFC822.
  50 format_month :: Month -> String
  51 format_month month = take 3 (show month)
  52
  53
  54 -- |Takes an offset from UTC (in seconds) and returns the four-digit
  55 -- offset as a 'String' in +hhmm format.
  56 format_timezone :: Int -> String
  57 format_timezone seconds =
  58     sign ++ pad_hh ++ pad_mm
  59     where
  60       seconds_norm = abs seconds
  61       hh = seconds_norm `div` 3600
  62       mm = (seconds_norm - (hh*3600)) `div` 60
  63       pad_hh = pad_left (show hh) 2
  64       pad_mm = pad_left (show mm) 2
  65       sign = if seconds < 0 then "-" else "+"
  66
  67
  68 -- |Takes a 'ClockTime' as an argument, and formats it as an RFC822 Date header.
  69 --
  70 -- See,
  71 --
  72 --   <http://cr.yp.to/immhf/date.html>
  73 --
  74 -- for information.
  75 format_clocktime :: ClockTime -> IO String
  76 format_clocktime ct = do
  77   caltime <- (toCalendarTime ct)
  78
  79   let days = pad_left (show (ctDay caltime)) 2
  80   let month = format_month (ctMonth caltime)
  81   let year = show $ ctYear caltime
  82   let hours = pad_left (show (ctHour caltime)) 2
  83   let minutes = pad_left (show (ctMin caltime)) 2
  84   let seconds = pad_left (show (ctSec caltime)) 2
  85   let timezone = format_timezone (ctTZ caltime)
  86
  87   return $ concat [(show $ ctWDay caltime) ++ ", ",
  88                    days ++ " ",
  89                    month ++ " ",
  90                    year ++ " ",
  91                    hours ++ ":",
  92                    minutes ++ ":",
  93                    seconds ++ " ",
  94                    timezone]
  95
  96
  97 -- |Constructs an RFC822 Date header with the current date/time.
  98 construct_date_header :: IO String
  99 construct_date_header = do
 100   date <- getClockTime
 101   format_clocktime date
 102
 103
 104
 105 -- |Takes a message as an argument, and passes it to the system's
 106 -- sendmail binary.
 107 sendmail :: Message -> IO (String, String, ExitCode)
 108 sendmail message = do
 109   let sendmail_args = ["-f",
 110                        (from message)]
 111
 112   (inh, outh, errh, ph) <-
 113       runInteractiveProcess "/usr/bin/sendmail" sendmail_args Nothing Nothing
 114
 115   outm <- newEmptyMVar
 116   outs <- hGetContents outh
 117
 118   errm <- newEmptyMVar
 119   errs <- hGetContents errh
 120
 121   forkIO $ hPutStr inh (show message) >> hClose inh
 122   forkIO $ evaluate (length outs) >> putMVar outm ()
 123   forkIO $ evaluate (length errs) >> putMVar errm ()
 124
 125   readMVar outm
 126   readMVar errm
 127
 128   ec <- waitForProcess ph
 129   return (outs, errs, ec)
 130
 131
 132 -- |The 'sendmail' function returns a three-tuple of its outputs,
 133 -- errors, and exit codes.  This function pretty-prints one of those
 134 -- three-tuples.
 135 print_sendmail_result :: (String, String, ExitCode) -> IO ()
 136 print_sendmail_result (outs, errs, ec) = do
 137     case ec of
 138       ExitSuccess -> return ()
 139       _ -> putStrLn $ concat ["Output: " ++ outs,
 140                               "\nErrors: " ++ errs,
 141                               "\nExit Code: " ++ (show ec)]