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 Data.Time (formatTime, getZonedTime)
  10 import System.Exit
  11 import System.Locale (defaultTimeLocale, rfc822DateFormat)
  12 import System.Process
  13 import System.IO (hClose, hGetContents, hPutStr)
  14
  15
  16 type Header = String
  17
  18 -- |A crude model of an RFC821 email message.
  19 data Message = Message { headers :: [Header],
  20                          subject :: String,
  21                          body    :: String,
  22                          from    :: String,
  23                          to      :: String }
  24              deriving (Eq)
  25
  26 -- |The default headers attached to each message.
  27 -- The MIME junk is needed for UTF-8 to work properly.
  28 -- Note that your mail server should support the 8BITMIME extension.
  29 default_headers :: [Header]
  30 default_headers = ["MIME-Version: 1.0",
  31                    "Content-Type: text/plain; charset=UTF-8",
  32                    "Content-Transfer-Encoding: 8bit"]
  33
  34 -- |Showing a message will print it in roughly RFC-compliant
  35 -- form. This form is sufficient for handing the message off to
  36 -- sendmail.
  37 instance Show Message where
  38     show m =
  39         concat [ if (length (headers m) == 0) then "" else (intercalate "\n" (headers m)) ++ "\n",
  40                  "Subject: " ++ (subject m) ++ "\n",
  41                  "From: " ++ (from m) ++ "\n",
  42                  "To: " ++ (to m) ++ "\n",
  43                  "\n",
  44                  (body m) ]
  45
  46
  47
  48 -- |Pad a string on the left with zeros until the entire string has
  49 -- length n.
  50 pad_left :: String -> Int -> String
  51 pad_left str n
  52          | n < (length str) = str
  53          | otherwise = (replicate num_zeros '0') ++ str
  54     where num_zeros = n - (length str)
  55
  56
  57
  58 -- | Constructs a 'String' in RFC822 date format for the current
  59 --   date/time.
  60 rfc822_now :: IO String
  61 rfc822_now = do
  62   date <- getZonedTime
  63   return $ formatTime defaultTimeLocale rfc822DateFormat date
  64
  65
  66
  67 -- |Takes a message as an argument, and passes it to the system's
  68 -- sendmail binary.
  69 sendmail :: Message -> IO (String, String, ExitCode)
  70 sendmail message = do
  71   let sendmail_args = ["-f",
  72                        (from message)]
  73
  74   (inh, outh, errh, ph) <-
  75       runInteractiveProcess "/usr/bin/sendmail" sendmail_args Nothing Nothing
  76
  77   outm <- newEmptyMVar
  78   outs <- hGetContents outh
  79
  80   errm <- newEmptyMVar
  81   errs <- hGetContents errh
  82
  83   _ <- forkIO $ hPutStr inh (show message) >> hClose inh
  84   _ <- forkIO $ evaluate (length outs) >> putMVar outm ()
  85   _ <- forkIO $ evaluate (length errs) >> putMVar errm ()
  86
  87   readMVar outm
  88   readMVar errm
  89
  90   ec <- waitForProcess ph
  91   return (outs, errs, ec)
  92
  93
  94 -- |The 'sendmail' function returns a three-tuple of its outputs,
  95 -- errors, and exit codes.  This function pretty-prints one of those
  96 -- three-tuples.
  97 print_sendmail_result :: (String, String, ExitCode) -> IO ()
  98 print_sendmail_result (outs, errs, ec) = do
  99     case ec of
 100       ExitSuccess -> return ()
 101       _ -> putStrLn $ concat ["Output: " ++ outs,
 102                               "\nErrors: " ++ errs,
 103                               "\nExit Code: " ++ (show ec)]