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