{- arch-tag: Sendmail utility
Copyright (c) 2004-2011 John Goerzen <jgoerzen@complete.org>

All rights reserved.

For license and copyright information, see the file LICENSE

{- |
   Module     : Network.Email.Sendmail
   Copyright  : Copyright (C) 2004-2011 John Goerzen
   License    : BSD3

   Maintainer : John Goerzen <jgoerzen@complete.org>
   Stability  : provisional
   Portability: portable

This Haskell module provides an interface to transmitting a mail message.

This is not compatible with Windows at this time.

Written by John Goerzen, jgoerzen\@complete.org

#if (defined(mingw32_HOST_OS) || defined(mingw32_TARGET_OS) || defined(__MINGW32__))
module Network.Email.Sendmail
module Network.Email.Sendmail(sendmail)

import System.Cmd.Utils
import System.Directory
import System.IO
import System.IO.Error
import qualified Control.Exception(try, IOException)

sendmails :: [String]
sendmails = ["/usr/sbin/sendmail",

findsendmail :: IO String
findsendmail =
    let worker [] = return "sendmail"
        worker (this:next) =
            e <- doesFileExist this
            if e then
               p <- getPermissions this
               if executable p then
                  return this
                  else worker next
               else worker next
        worker sendmails

{- | Transmits an e-mail message using the system's mail transport agent.

This function takes a message, a list of recipients, and an optional sender,
and transmits it using the system's MTA, sendmail.

If @sendmail@ is on the @PATH@, it will be used; otherwise, a list of system
default locations will be searched.

A failure will be logged, since this function uses 'System.Cmd.Utils.safeSystem'

This function will first try @sendmail@.  If it does not exist, an error is
logged under @System.Cmd.Utils.pOpen3@ and various default @sendmail@ locations
are tried.  If that still fails, an error is logged and an exception raised.

sendmail :: Maybe String                -- ^ The envelope from address.  If not specified, takes the system's default, which is usually based on the effective userid of the current process.  This is not necessarily what you want, so I recommend specifying it.
         -> [String]                    -- ^ A list of recipients for your message.  An empty list is an error.
         -> String                      -- ^ The message itself.
         -> IO ()
sendmail _ [] _ = fail "sendmail: no recipients specified"
sendmail Nothing recipients msg = sendmail_worker recipients msg
sendmail (Just from) recipients msg =
    sendmail_worker (("-f" ++ from) : recipients) msg

sendmail_worker :: [String] -> String -> IO ()
sendmail_worker args msg =
    let func h = hPutStr h msg
        --pOpen WriteToPipe "/usr/sbin/sendmail" args func
        rv <- Control.Exception.try (pOpen WriteToPipe "sendmail" args func)
        case rv of
            Right x -> return x
            Left (_ :: Control.Exception.IOException) -> do
                      sn <- findsendmail
                      r <- pOpen WriteToPipe sn args func
                      return $! r