import Control.Arrow                   ( second )
import Control.Concurrent              ( forkIO, threadDelay )
import Control.Exception               ( mask_, catch )
import Control.Monad                   ( when )
import qualified Data.ByteString as B  ( ByteString )
import qualified Data.ByteString.Char8 as B  ( putStrLn )
import Data.Char                       ( isDigit )
import Network.HaskellNet.IMAP.Connection as I  ( IMAPConnection )
import Network.HaskellNet.IMAP   as I  ( list, select, search, SearchQuery(..), fetch
                                       , connectIMAPPort, login 
                                       )
import Network.Socket            as S  ( HostName, PortNumber )
import Prelude hiding                  (catch)
import System.Directory                ( canonicalizePath )
import System.Environment              ( getArgs )
import System.Exit                     ( exitFailure )
import System.IO.Error                 ( isDoesNotExistError )

import SSLWrap                         ( mapSSL )


main :: IO ()
main = do
  let config_file = "config.txt"
      parseConfig = map (second (drop 1) . break (=='=')) . lines
      defaultConfig = unlines 
                        [ "hostname=imap.gmail.com"
                        , "port=993"
                        , "username=facundominguez@gmail.com"
                        , "passwd=haskellisnice"
                        , "ssl_wrap_port=3004"
                        ]
  opts <- catch (fmap parseConfig$ readFile config_file)$ \e -> do
            when (isDoesNotExistError e)$ do
                writeFile config_file defaultConfig
                putStrLn$ unlines 
                  [ ""
                  , "Thanks for using imapget!"
                  , ""
                  , "You need to edit a configuration file to specify where to connect"
                  , "and which username and password to use."
                  , ""
                  , "I just created a default ./"++config_file++" file."
                  , "Please edit it to set your options."
                  ]
            exitFailure

  let readConfig name action = maybe (putStrLn$ "error: missing "++name++" option from "++config_file) action$ lookup name opts

  readConfig "hostname"$ \hostname ->
   readConfig "port"$ \port ->
    readConfig "username"$ \username ->
     readConfig "passwd"$ \passwd ->
      readConfig "ssl_wrap_port"$ \ssl_wrap_port -> do

  args <- getArgs

  case args of
    ["list"] | all isDigit port ->
         main' IMAPConf 
                { icHostname = hostname
                , icPort = fromIntegral (read port :: Int)
                , icUsername = username 
                , icPasswd = passwd 
                , icSSLWrapPort = fromIntegral (read ssl_wrap_port :: Int)
                } 
                Nothing
    ["fetch",label] | all isDigit port ->
         main' IMAPConf 
                { icHostname =hostname
                , icPort = fromIntegral (read port :: Int)
                , icUsername = username 
                , icPasswd = passwd 
                , icSSLWrapPort = fromIntegral (read ssl_wrap_port :: Int)
                }
                (Just label)
    _ -> putStrLn "USAGE: imapget [list|fetch label]"


type UserName = String
type Password = String
type Label = String

data IMAPConf = IMAPConf 
    { icHostname :: S.HostName
    , icPort :: S.PortNumber
    , icUsername :: UserName
    , icPasswd :: Password
    , icSSLWrapPort :: S.PortNumber
    }

main' :: IMAPConf -> Maybe Label -> IO ()
main' conf mlabel = do 
  case mlabel of
    Nothing -> do
        withIMAP conf$ \ic -> do
            putStrLn$ "Fetching mailbox ..."
            I.list ic >>= mapM_ (putStrLn . snd)
    Just label -> getEmails conf label B.putStrLn 


getEmails :: IMAPConf -> Label -> (B.ByteString -> IO a) -> IO ()
getEmails c label f = withIMAP c$ \ic -> do
  putStrLn$ "Selecting "++label++" ..."
  I.select ic label
  putStrLn$ "Retrieving "++label++" ..."
  I.search ic [ALLs]
     >>= mapM_ (\uid -> I.fetch ic uid >>= f)
       


withIMAP :: IMAPConf -> (I.IMAPConnection -> IO a) -> IO a
withIMAP c action = do
  -- launch thread for wrapping tcp with SSL
  cafile <- canonicalizePath "cacert.pem"
  _ <- mask_$ forkIO$ mapSSL cafile (icSSLWrapPort c) (icHostname c) (icPort c)
  
  -- start imap communication
  threadDelay$ 500*1000
  putStrLn$ "Connecting to "++icHostname c++":"++show (icPort c)++" (wrapping with ssl through localhost:"++show (icSSLWrapPort c)++") ..."
  ic <- connectIMAPPort "localhost" (icSSLWrapPort c)
  putStrLn$ "Authenticating user "++icUsername c++" ..."
  I.login ic (icUsername c) (icPasswd c)
  action ic