src/Main.hs

   1 module Main
   2 where
   3
   4 import Control.Concurrent (forkIO, threadDelay)
   5 import Control.Monad (forever, when)
   6 import Data.Maybe (fromJust)
   7 import System.Exit (ExitCode(..), exitWith)
   8 import System.IO (hPutStrLn, stderr)
   9
  10 import CommandLine
  11 import ExitCodes
  12 import Mail
  13 import Twitter.Http
  14 import Twitter.Status
  15 import Twitter.User
  16
  17
  18 -- |A wrapper around threadDelay which takes seconds instead of
  19 -- microseconds as its argument.
  20 thread_sleep :: Int -> IO ()
  21 thread_sleep seconds = do
  22   let microseconds = seconds * (10 ^ (6 :: Int))
  23   threadDelay microseconds
  24
  25
  26 -- |Given a 'Message', 'Status', and default date, update that
  27 -- message's body and subject with the information contained in the
  28 -- status. Adds a /Date: / header, and returns the updated message.
  29 message_from_status :: Message -> String -> Status -> Message
  30 message_from_status message default_date status =
  31   message { subject = "Twat: " ++ (screen_name (user status)),
  32             body    = (pretty_print status),
  33             headers = ((headers message) ++ ["Date: " ++ date])}
  34   where
  35     -- Use the Status' created_at date if it can be coerced into
  36     -- RFC822 format.
  37     date = case (created_at_to_rfc822 $ created_at status) of
  38              Nothing -> default_date
  39              Just c  -> c
  40
  41 -- |This is the main recursive loop. It takes a length of time to
  42 -- delay (in seconds), a username, a latest_status_id, and optionally
  43 -- a 'Message' as arguments. The latest_status_id is the last status
  44 -- (that we know of) to be posted to username's Twitter account. If we
  45 -- find any newer statuses when we check, they are printed and
  46 -- optionally emailed (if a 'Message' was supplied). Then, the process
  47 -- repeats.
  48 recurse :: Int -> String -> Integer -> (Maybe Message) -> IO ()
  49 recurse delay username latest_status_id maybe_message = do
  50     thread_sleep delay
  51     xmldata <- get_user_new_statuses username latest_status_id
  52
  53     -- Parsing an empty result can blow up. Just pretend there are
  54     -- no new statuses in that case.
  55     let new_statuses = case xmldata of
  56                          Just xml -> parse_statuses xml
  57                          Nothing  -> []
  58
  59     case (length new_statuses) of
  60       0 ->
  61         recurse delay username latest_status_id maybe_message
  62       _ -> do
  63         let new_latest_status_id = get_max_status_id new_statuses
  64         _ <- mapM (putStrLn . pretty_print) new_statuses
  65
  66         case maybe_message of
  67           Nothing -> do
  68              recurse delay username new_latest_status_id maybe_message
  69              return ()
  70           Just message -> do
  71              default_date <- rfc822_now
  72              let messages = map (message_from_status message (default_date)) new_statuses
  73              sendmail_results <- mapM sendmail messages
  74              _ <- mapM print_sendmail_result sendmail_results
  75              recurse delay username new_latest_status_id maybe_message
  76              return ()
  77
  78
  79 -- |Try continually to download username's timeline, and determine the
  80 -- latest status id to be posted once we have done so.
  81 get_latest_status_id :: Int -> String -> IO Integer
  82 get_latest_status_id delay username = do
  83   xmldata <- get_user_timeline username
  84
  85   let initial_statuses = case xmldata of
  86                            Just xml -> parse_statuses xml
  87                            Nothing -> []
  88
  89   case (length initial_statuses) of
  90     0 -> do
  91       -- If the HTTP part barfs, try again after a while.
  92       putStrLn ("Couldn't retrieve " ++ username ++ "'s timeline. Retrying...")
  93       thread_sleep delay
  94       get_latest_status_id delay username
  95     _ -> return (get_max_status_id initial_statuses)
  96
  97
  98
  99 -- |This function wraps two steps. First, we need to find the latest
 100 -- status id posted by username. Once we have that, we can begin the
 101 -- recursive loop that checks for updates forever. The message
 102 -- argument is optional and is passed to recurse in case the updates
 103 -- should be emailed.
 104 run_twat :: Int -> Maybe Message -> String -> IO ()
 105 run_twat delay message username = do
 106   latest_status_id <- get_latest_status_id delay username
 107   recurse delay username latest_status_id message
 108   return ()
 109
 110
 111 -- |The main function just parses the command-line arguments and then
 112 -- forks off calls to 'run_twat' for each supplied username. After
 113 -- forking, main loops forever.
 114 main :: IO ()
 115 main = do
 116   errors <- parse_errors
 117
 118   -- If there  were errors parsing the command-line options,
 119   -- print them and exit.
 120   when (not (null errors)) $ do
 121       hPutStrLn stderr (concat errors)
 122       putStrLn help_text
 123       exitWith (ExitFailure exit_args_parse_failed)
 124
 125   -- Next, check to see if the 'help' option was passed to the
 126   -- program. If it was, display the help, and exit successfully.
 127   help_opt_set <- help_set
 128   when help_opt_set $ do
 129       putStrLn help_text
 130       exitWith ExitSuccess
 131
 132   usernames <- parse_usernames
 133
 134   -- If we have both a "To" and "From" address, we'll create a
 135   -- message object to be passed to all of our threads.
 136   to_address <- to_email_address
 137   from_address <- from_email_address
 138   let message = case to_address of
 139                   Nothing -> Nothing
 140                   Just toaddr ->
 141                       case from_address of
 142                         Nothing -> Nothing
 143                         Just fromaddr ->
 144                             Just (Message { headers = default_headers,
 145                                             body = "",
 146                                             subject = "",
 147                                             to = toaddr,
 148                                             from = fromaddr })
 149
 150   -- This should be safe since we checked for parse errors earlier.
 151   delay <- fmap fromJust heartbeat
 152
 153   -- Execute run_twat on each username in a new thread.
 154   _ <- mapM (forkIO . (run_twat delay message)) usernames
 155
 156   _ <- forever $ do
 157     -- This thread (the one executing main) doesn't do anything,
 158     -- but when it terminates, so do all the threads we forked.
 159     -- As a result, we need to keep this thread on life support.
 160     thread_sleep delay
 161
 162   return ()
 163
 164
 165 -- |A debugging tool that will parse, print, and email a single status
 166 -- (given by its id).
 167 twat_single_status :: Integer -> (Maybe Message) -> IO ()
 168 twat_single_status the_status_id maybe_message = do
 169     xmldata <- get_status the_status_id
 170
 171     -- Parsing an empty result can blow up. Just pretend there are
 172     -- no new statuses in that case.
 173     let statuses = case xmldata of
 174                      Just xml -> parse_status xml
 175                      Nothing  -> []
 176
 177     case (length statuses) of
 178       0 -> do
 179         putStrLn "No statuses returned."
 180         return ()
 181       _ -> do
 182         _ <- mapM (putStrLn . pretty_print) statuses
 183
 184         case maybe_message of
 185           Nothing -> do
 186              putStrLn "No message object given."
 187              return ()
 188           Just message -> do
 189              default_date <- rfc822_now
 190              let messages = map (message_from_status message (default_date)) statuses
 191              sendmail_results <- mapM sendmail messages
 192              _ <- mapM print_sendmail_result sendmail_results
 193              return ()