{-# LANGUAGE OverloadedStrings, ScopedTypeVariables, RecordWildCards #-}
module Network.Mail.SMTP
    ( -- * Main interface
      sendMail
    , sendMail'
    , sendMailWithLogin
    , sendMailWithLogin'
    , simpleMail
    , plainTextPart
    , htmlPart
    , filePart

    -- * Types
    , module Network.Mail.SMTP.Types
    , SMTPConnection

      -- * Network.Mail.Mime's sendmail interface (reexports)
    , sendmail
    , sendmailCustom
    , renderSendMail
    , renderSendMailCustom

      -- * Establishing Connection
    , connectSMTP
    , connectSMTP'

      -- * Operation to a Connection
    , sendCommand
    , login
    , closeSMTP
    , renderAndSend
    )
    where

import Network.Mail.SMTP.Auth
import Network.Mail.SMTP.Types

import System.IO
import System.FilePath (takeFileName)

import Control.Monad (unless)
import Data.Monoid
import Data.Char (isDigit)

import Network
import Network.BSD (getHostName)
import Network.Mail.Mime hiding (simpleMail)

import Data.ByteString (ByteString)
import qualified Data.ByteString.Char8 as BS
import qualified Data.ByteString.Lazy as B
import qualified Data.ByteString as S
import qualified Data.Text as T
import qualified Data.Text.Lazy as TL
import qualified Data.Text.Lazy.Encoding as TL
import Data.Text.Encoding

data SMTPConnection = SMTPC !Handle ![ByteString]

instance Eq SMTPConnection where
    (==) (SMTPC a _) (SMTPC b _) = a == b

-- | Connect to an SMTP server with the specified host and default port (25)
connectSMTP :: HostName     -- ^ name of the server
            -> IO SMTPConnection
connectSMTP = flip connectSMTP' 25

-- | Connect to an SMTP server with the specified host and port
connectSMTP' :: HostName     -- ^ name of the server
                -> PortNumber -- ^ port number
                -> IO SMTPConnection
connectSMTP' hostname port =
    connectTo hostname (PortNumber port) >>= connectStream

-- | Attemp to send a 'Command' to the SMTP server once
tryOnce :: SMTPConnection -> Command -> ReplyCode -> IO ByteString
tryOnce = tryCommand 1

-- | Repeatedly attempt to send a 'Command' to the SMTP server
tryCommand :: Int -> SMTPConnection -> Command -> ReplyCode
           -> IO ByteString
tryCommand tries st cmd expectedReply = do
    (code, msg) <- sendCommand st cmd
    if code == expectedReply 
      then return msg
      else if tries > 1
        then tryCommand (tries - 1) st cmd expectedReply
        else do
          closeSMTP st
          fail $ "Unexpected reply to: " ++ show cmd ++ 
            ", Expected reply code: " ++ show expectedReply ++
            ", Got this instead: " ++ show code ++ " " ++ show msg

-- | Create an 'SMTPConnection' from an already connected Handle
connectStream :: Handle -> IO SMTPConnection
connectStream st =
    do (code1, _) <- parseResponse st
       unless (code1 == 220) $
              do hClose st
                 fail "cannot connect to the server"
       senderHost <- getHostName
       msg <- tryCommand 3 (SMTPC st []) (EHLO $ BS.pack senderHost) 250
       return (SMTPC st (tail $ BS.lines msg))

parseResponse :: Handle -> IO (ReplyCode, ByteString)
parseResponse st =
    do (code, bdy) <- readLines
       return (read $ BS.unpack code, BS.unlines bdy)
    where readLines =
              do l <- BS.hGetLine st
                 let (c, bdy) = BS.span isDigit l
                 if not (BS.null bdy) && BS.head bdy == '-'
                    then do (c2, ls) <- readLines
                            return (c2, BS.tail bdy:ls)
                    else return (c, [BS.tail bdy])


-- | Send a 'Command' to the SMTP server
sendCommand :: SMTPConnection -> Command -> IO (ReplyCode, ByteString)
sendCommand (SMTPC conn _) (DATA dat) =
    do bsPutCrLf conn "DATA"
       (code, _) <- parseResponse conn
       unless (code == 354) $ fail "this server cannot accept any data."
       mapM_ sendLine $ split dat
       sendLine dot
       parseResponse conn
    where 
      sendLine = bsPutCrLf conn
      split = map (padDot . stripCR) . BS.lines
      -- remove \r at the end of a line
      stripCR s = if cr `BS.isSuffixOf` s then BS.init s else s
      -- duplicate . at the start of a line
      padDot s = if dot `BS.isPrefixOf` s then dot <> s else s
      cr = BS.pack "\r"
      dot = BS.pack "."


sendCommand (SMTPC conn _) (AUTH LOGIN username password) =
    do bsPutCrLf conn command
       _ <- parseResponse conn
       bsPutCrLf conn userB64
       _ <- parseResponse conn
       bsPutCrLf conn passB64
       (code, msg) <- parseResponse conn
       unless (code == 235) $ fail "authentication failed."
       return (code, msg)
    where command = "AUTH LOGIN"
          (userB64, passB64) = encodeLogin username password
sendCommand (SMTPC conn _) (AUTH at username password) =
    do bsPutCrLf conn command
       (code, msg) <- parseResponse conn
       unless (code == 334) $ fail "authentication failed."
       bsPutCrLf conn $ auth at (BS.unpack msg) username password
       parseResponse conn
    where command = BS.pack $ unwords ["AUTH", show at]
sendCommand (SMTPC conn _) meth =
    do bsPutCrLf conn command
       parseResponse conn
    where command = case meth of
                      (HELO param) -> "HELO " <> param
                      (EHLO param) -> "EHLO " <> param
                      (MAIL param) -> "MAIL FROM:<" <> param <> ">"
                      (RCPT param) -> "RCPT TO:<" <> param <> ">"
                      (EXPN param) -> "EXPN " <> param
                      (VRFY param) -> "VRFY " <> param
                      (HELP msg)   -> if BS.null msg
                                        then "HELP\r\n"
                                        else "HELP " <> msg
                      NOOP         -> "NOOP"
                      RSET         -> "RSET"
                      QUIT         -> "QUIT"
                      DATA{}       -> 
                          error "BUG: DATA pattern should be matched by sendCommand patterns"
                      AUTH{}       ->
                          error "BUG: AUTH pattern should be matched by sendCommand patterns"

-- | Send 'QUIT' and close the connection.
closeSMTP :: SMTPConnection -> IO ()
closeSMTP c@(SMTPC conn _) = sendCommand c QUIT >> hClose conn

-- | Sends a rendered mail to the server. 
sendRenderedMail :: ByteString   -- ^ sender mail
            -> [ByteString] -- ^ receivers
            -> ByteString   -- ^ data
            -> SMTPConnection
            -> IO ()
sendRenderedMail sender receivers dat conn = do
    _ <- tryOnce conn (MAIL sender) 250
    mapM_ (\r -> tryOnce conn (RCPT r) 250) receivers
    _ <- tryOnce conn (DATA dat) 250
    return ()

-- | Render a 'Mail' to a 'ByteString' then send it over the specified
-- 'SMTPConnection'
renderAndSend ::SMTPConnection -> Mail -> IO ()
renderAndSend conn mail@Mail{..} = do
    rendered <- lazyToStrict `fmap` renderMail' mail
    sendRenderedMail from to rendered conn
  where enc  = encodeUtf8 . addressEmail 
        from = enc mailFrom
        to   = map enc mailTo

-- | Connect to an SMTP server, send a 'Mail', then disconnect.  Uses the default port (25).
sendMail :: HostName -> Mail -> IO ()
sendMail host mail = do
  con <- connectSMTP host
  renderAndSend con mail
  closeSMTP con

-- | Connect to an SMTP server, send a 'Mail', then disconnect.
sendMail' :: HostName -> PortNumber -> Mail -> IO ()
sendMail' host port mail = do
  con <- connectSMTP' host port
  renderAndSend con mail
  closeSMTP con

-- | Connect to an SMTP server, login, send a 'Mail', disconnect.  Uses the default port (25).
sendMailWithLogin :: HostName -> UserName -> Password -> Mail -> IO ()
sendMailWithLogin host user pass mail = do
  con <- connectSMTP host
  _ <- sendCommand con (AUTH LOGIN user pass)
  renderAndSend con mail
  closeSMTP con

-- | Connect to an SMTP server, login, send a 'Mail', disconnect.
sendMailWithLogin' :: HostName -> PortNumber -> UserName -> Password -> Mail -> IO ()
sendMailWithLogin' host port user pass mail = do
  con <- connectSMTP' host port
  _ <- sendCommand con (AUTH LOGIN user pass)
  renderAndSend con mail
  closeSMTP con

-- | A convenience function that sends 'AUTH' 'LOGIN' to the server
login :: SMTPConnection -> UserName -> Password -> IO (ReplyCode, ByteString)
login con user pass = sendCommand con (AUTH LOGIN user pass)

-- | A simple interface for generating a 'Mail' with a plantext body and
-- an optional HTML body.
simpleMail :: Address   -- ^ from
           -> [Address] -- ^ to
           -> [Address] -- ^ CC
           -> [Address] -- ^ BCC
           -> T.Text -- ^ subject
           -> [Part] -- ^ list of parts (list your preferred part last)
           -> Mail
simpleMail from to cc bcc subject parts =
    Mail { mailFrom = from
         , mailTo   = to
         , mailCc   = cc
         , mailBcc  = bcc
         , mailHeaders = [ ("Subject", subject) ]
         , mailParts = [parts]
         }

-- | Construct a plain text 'Part'
plainTextPart :: TL.Text -> Part
plainTextPart = Part "text/plain; charset=utf-8" 
              QuotedPrintableText Nothing [] . TL.encodeUtf8

-- | Construct an html 'Part'
htmlPart :: TL.Text -> Part
htmlPart = Part "text/html; charset=utf-8" 
             QuotedPrintableText Nothing [] . TL.encodeUtf8

-- | Construct a file attachment 'Part'
filePart :: T.Text -- ^ content type
         -> FilePath -- ^ path to file 
         -> IO Part
filePart ct fp = do
    content <- B.readFile fp
    return $ Part ct Base64 (Just $ T.pack (takeFileName fp)) [] content 

lazyToStrict :: B.ByteString -> S.ByteString
lazyToStrict = S.concat . B.toChunks

crlf :: BS.ByteString
crlf = BS.pack "\r\n"

bsPutCrLf :: Handle -> ByteString -> IO ()
bsPutCrLf h s = BS.hPut h s >> BS.hPut h crlf >> hFlush h