src/Mail.hs

   1 -- |Email functions and data types.
   2
   3 module Mail
   4 where
   5
   6 import Control.Concurrent
   7 import Control.Exception (evaluate)
   8 import Data.List (intercalate)
   9 import System.Exit
  10 import System.Process
  11 import System.Time (CalendarTime(..), ClockTime, getClockTime, Month, toCalendarTime)
  12 import System.IO (hClose, hGetContents, hPutStr)
  13
  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 -- |The default headers attached to each message.
  26 -- The MIME junk is needed for UTF-8 to work properly.
  27 -- Note that your mail server should support the 8BITMIME extension.
  28 default_headers :: [Header]
  29 default_headers = ["MIME-Version: 1.0",
  30                    "Content-Type: text/plain; charset=UTF-8",
  31                    "Content-Transfer-Encoding: 8bit"]
  32
  33 -- |Showing a message will print it in roughly RFC-compliant
  34 -- form. This form is sufficient for handing the message off to
  35 -- sendmail.
  36 instance Show Message where
  37     show m =
  38         concat [ if (length (headers m) == 0) then "" else (intercalate "\n" (headers m)) ++ "\n",
  39                  "Subject: " ++ (subject m) ++ "\n",
  40                  "From: " ++ (from m) ++ "\n",
  41                  "To: " ++ (to m) ++ "\n",
  42                  "\n",
  43                  (body m) ]
  44
  45
  46
  47 -- |Pad a string on the left with zeros until the entire string has
  48 -- length n.
  49 pad_left :: String -> Int -> String
  50 pad_left str n
  51          | n < (length str) = str
  52          | otherwise = (replicate num_zeros '0') ++ str
  53     where num_zeros = n - (length str)
  54
  55
  56
  57 -- |Formats a month name according to RFC822.
  58 format_month :: Month -> String
  59 format_month month = take 3 (show month)
  60
  61
  62 -- |Takes an offset from UTC (in seconds) and returns the four-digit
  63 -- offset as a 'String' in +hhmm format.
  64 format_timezone :: Int -> String
  65 format_timezone seconds =
  66     sign ++ pad_hh ++ pad_mm
  67     where
  68       seconds_norm = abs seconds
  69       hh = seconds_norm `div` 3600
  70       mm = (seconds_norm - (hh*3600)) `div` 60
  71       pad_hh = pad_left (show hh) 2
  72       pad_mm = pad_left (show mm) 2
  73       sign = if seconds < 0 then "-" else "+"
  74
  75
  76 -- |Takes a 'ClockTime' as an argument, and formats it as an RFC822 Date header.
  77 --
  78 -- See,
  79 --
  80 --   <http://cr.yp.to/immhf/date.html>
  81 --
  82 -- for information.
  83 format_clocktime :: ClockTime -> IO String
  84 format_clocktime ct = do
  85   caltime <- (toCalendarTime ct)
  86
  87   let days = pad_left (show (ctDay caltime)) 2
  88   let month = format_month (ctMonth caltime)
  89   let year = show $ ctYear caltime
  90   let hours = pad_left (show (ctHour caltime)) 2
  91   let minutes = pad_left (show (ctMin caltime)) 2
  92   let seconds = pad_left (show (ctSec caltime)) 2
  93   let timezone = format_timezone (ctTZ caltime)
  94
  95   return $ concat [(show $ ctWDay caltime) ++ ", ",
  96                    days ++ " ",
  97                    month ++ " ",
  98                    year ++ " ",
  99                    hours ++ ":",
 100                    minutes ++ ":",
 101                    seconds ++ " ",
 102                    timezone]
 103
 104
 105 -- |Constructs an RFC822 Date header with the current date/time.
 106 construct_date_header :: IO String
 107 construct_date_header = do
 108   date <- getClockTime
 109   format_clocktime date
 110
 111
 112
 113 -- |Takes a message as an argument, and passes it to the system's
 114 -- sendmail binary.
 115 sendmail :: Message -> IO (String, String, ExitCode)
 116 sendmail message = do
 117   let sendmail_args = ["-f",
 118                        (from message)]
 119
 120   (inh, outh, errh, ph) <-
 121       runInteractiveProcess "/usr/bin/sendmail" sendmail_args Nothing Nothing
 122
 123   outm <- newEmptyMVar
 124   outs <- hGetContents outh
 125
 126   errm <- newEmptyMVar
 127   errs <- hGetContents errh
 128
 129   _ <- forkIO $ hPutStr inh (show message) >> hClose inh
 130   _ <- forkIO $ evaluate (length outs) >> putMVar outm ()
 131   _ <- forkIO $ evaluate (length errs) >> putMVar errm ()
 132
 133   readMVar outm
 134   readMVar errm
 135
 136   ec <- waitForProcess ph
 137   return (outs, errs, ec)
 138
 139
 140 -- |The 'sendmail' function returns a three-tuple of its outputs,
 141 -- errors, and exit codes.  This function pretty-prints one of those
 142 -- three-tuples.
 143 print_sendmail_result :: (String, String, ExitCode) -> IO ()
 144 print_sendmail_result (outs, errs, ec) = do
 145     case ec of
 146       ExitSuccess -> return ()
 147       _ -> putStrLn $ concat ["Output: " ++ outs,
 148                               "\nErrors: " ++ errs,
 149                               "\nExit Code: " ++ (show ec)]