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.  The MIME junk is
  27 --   needed for UTF-8 to work properly. Note that your mail server
  28 --   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 (or compatible).
  37 instance Show Message where
  38   show m =
  39     concat [ formatted_headers,
  40              "Subject: " ++ (subject m) ++ "\n",
  41              "From: " ++ (from m) ++ "\n",
  42              "To: " ++ (to m) ++ "\n",
  43              "\n",
  44              (body m) ]
  45     where
  46       formatted_headers =
  47         if null (headers m)
  48         then ""
  49         else (intercalate "\n" (headers m)) ++ "\n"
  50
  51
  52 -- |Pad a string on the left with zeros until the entire string has
  53 -- length n.
  54 pad_left :: String -> Int -> String
  55 pad_left str n
  56  | n < (length str) = str
  57  | otherwise = (replicate num_zeros '0') ++ str
  58    where num_zeros = n - (length str)
  59
  60
  61
  62 -- | Constructs a 'String' in RFC822 date format for the current
  63 --   date/time.
  64 rfc822_now :: IO String
  65 rfc822_now = do
  66   date <- getZonedTime
  67   return $ formatTime defaultTimeLocale rfc822DateFormat date
  68
  69
  70
  71 -- |Takes a message as an argument, and passes it to the system's
  72 -- sendmail (or compatible) binary.
  73 sendmail :: FilePath -> Message -> IO (String, String, ExitCode)
  74 sendmail sendmail_path message = do
  75   let sendmail_args = ["-f",
  76                        (from message),
  77                        (to message)]
  78
  79   (inh, outh, errh, ph) <-
  80       runInteractiveProcess sendmail_path sendmail_args Nothing Nothing
  81
  82   outm <- newEmptyMVar
  83   outs <- hGetContents outh
  84
  85   errm <- newEmptyMVar
  86   errs <- hGetContents errh
  87
  88   _ <- forkIO $ hPutStr inh (show message) >> hClose inh
  89   _ <- forkIO $ evaluate (length outs) >> putMVar outm ()
  90   _ <- forkIO $ evaluate (length errs) >> putMVar errm ()
  91
  92   readMVar outm
  93   readMVar errm
  94
  95   ec <- waitForProcess ph
  96   return (outs, errs, ec)
  97
  98
  99 -- |The 'sendmail' function returns a three-tuple of its outputs,
 100 -- errors, and exit codes.  This function pretty-prints one of those
 101 -- three-tuples.
 102 print_sendmail_result :: (String, String, ExitCode) -> IO ()
 103 print_sendmail_result (outs, errs, ec) = do
 104   case ec of
 105     ExitSuccess -> return ()
 106     _ -> putStrLn $ concat ["Output: " ++ outs,
 107                             "\nErrors: " ++ errs,
 108                             "\nExit Code: " ++ (show ec)]