src/Main.hs

   1 module Main
   2 where
   3
   4 import Control.Concurrent (forkIO, threadDelay)
   5 import Control.Monad (forever, when)
   6 import Data.Aeson (decode)
   7 import Data.List ((\\))
   8 import Data.Monoid ((<>))
   9 import Data.Time.LocalTime (TimeZone, getCurrentTimeZone)
  10 import System.Exit (ExitCode(..), exitWith)
  11 import System.IO (hPutStrLn, stderr)
  12
  13 import CommandLine
  14 import Configuration (Cfg(..), default_config, merge_optional)
  15 import ExitCodes (exit_no_usernames)
  16 import qualified OptionalConfiguration as OC
  17 import Mail (
  18   Message(..),
  19   default_headers,
  20   print_sendmail_result,
  21   rfc822_now,
  22   sendmail
  23   )
  24 import Twitter.Http
  25 import Twitter.Status
  26 import Twitter.User
  27 import Usernames (Usernames(..))
  28
  29 -- | A wrapper around threadDelay which takes seconds instead of
  30 --   microseconds as its argument.
  31 thread_sleep :: Int -> IO ()
  32 thread_sleep seconds = do
  33   let microseconds = seconds * (10 ^ (6 :: Int))
  34   threadDelay microseconds
  35
  36
  37 -- | Given a 'Message', 'Status', and date, update that message's body
  38 -- and subject with the information contained in the status. Adds a
  39 -- /Date: / header, and returns the updated message.
  40 message_from_status :: Maybe TimeZone -> Message -> String -> Status -> Message
  41 message_from_status mtz message default_date status =
  42   message { subject = "Halcyon: " ++ (screen_name (user status)),
  43             body    = (pretty_print mtz status),
  44             headers = ((headers message) ++ ["Date: " ++ date])}
  45   where
  46     date =
  47       case created_at status of
  48         Nothing -> default_date
  49         Just c  -> utc_time_to_rfc822 mtz c
  50
  51 -- | If the given Message is not Nothing, send a copy of it for every
  52 -- Status in the list.
  53 send_messages :: Cfg -> Maybe TimeZone -> Maybe Message -> [Status] -> IO ()
  54 send_messages cfg mtz maybe_message statuses =
  55   case maybe_message of
  56     Nothing -> return ()
  57     Just message -> do
  58       default_date <- rfc822_now
  59       let mfs = message_from_status mtz message default_date
  60       let messages = map mfs statuses
  61       sendmail_results <- mapM sendmail' messages
  62       _ <- mapM print_sendmail_result sendmail_results
  63       return ()
  64   where
  65     sendmail' = sendmail (sendmail_path cfg)
  66
  67 -- | Display the number of skipped replies if ignore_replies is true
  68 --   and verbose is enabled.
  69 mention_replies :: Cfg -> [Status] -> IO ()
  70 mention_replies cfg ss = do
  71   let replies  = filter reply ss
  72   when ((ignore_replies cfg) && (verbose cfg)) $ do
  73     let countstr = show $ length replies
  74     putStrLn $ "Ignoring " ++ countstr ++ " replies."
  75
  76
  77 -- | Display the number of skipped retweets if ignore_retweets is true
  78 --   and verbose is enabled.
  79 mention_retweets :: Cfg -> [Status] -> IO ()
  80 mention_retweets cfg ss = do
  81   let retweets = filter retweeted ss
  82   when ((ignore_retweets cfg) && (verbose cfg)) $ do
  83     let countstr = show $ length retweets
  84     putStrLn  $ "Ignoring " ++ countstr ++ " retweets."
  85
  86
  87
  88 -- | Filter out replies/retweets based on the configuration.
  89 filter_statuses :: Cfg -> [Status] -> [Status]
  90 filter_statuses cfg ss =
  91   good_statuses
  92   where
  93   replies  = filter reply ss
  94   retweets = filter retweeted ss
  95
  96   good_statuses' = if (ignore_replies cfg)
  97                    then ss \\ replies
  98                    else ss
  99
 100   good_statuses = if (ignore_retweets cfg)
 101                   then good_statuses' \\ retweets
 102                   else good_statuses'
 103
 104
 105
 106 -- | This is the main recursive loop. It takes a the configuration, a
 107 --   username, a latest_status_id, and optionally a 'Message' as
 108 --   arguments. The latest_status_id is the last status (that we know
 109 --   of) to be posted to username's Twitter account. If we find any
 110 --   newer statuses when we check, they are printed and optionally
 111 --   emailed (if a 'Message' was supplied). Then, the process repeats.
 112 recurse :: Cfg -> String -> Integer -> (Maybe Message) -> IO ()
 113 recurse cfg username latest_status_id maybe_message = do
 114   thread_sleep (heartbeat cfg)
 115   timeline <- get_user_new_statuses cfg username latest_status_id
 116
 117   -- FIXME
 118   let Just new_statuses = decode timeline :: Maybe Timeline
 119
 120   case (length new_statuses) of
 121     0 ->
 122       do_recurse latest_status_id
 123     _ -> do
 124
 125       mention_replies cfg new_statuses
 126       mention_retweets cfg new_statuses
 127
 128       let good_statuses = filter_statuses cfg new_statuses
 129
 130       tz <- getCurrentTimeZone
 131       let mtz = Just tz
 132       mapM_ (putStrLn . (pretty_print mtz)) good_statuses
 133
 134       send_messages cfg mtz maybe_message good_statuses
 135
 136       let new_latest_status_id = get_max_status_id new_statuses
 137       do_recurse new_latest_status_id
 138
 139   where
 140     -- This lets us write all of these parameters once rather
 141     -- than... more than once.
 142     do_recurse :: Integer -> IO ()
 143     do_recurse lsi = recurse cfg username lsi maybe_message
 144
 145
 146 -- | Try continually to download username's timeline, and determine the
 147 --   latest status id to be posted once we have done so.
 148 get_latest_status_id :: Cfg -> String -> IO Integer
 149 get_latest_status_id cfg username = do
 150   let delay = heartbeat cfg
 151   timeline <- get_user_timeline cfg username
 152   let Just initial_timeline = decode timeline :: Maybe Timeline
 153
 154   case (length initial_timeline) of
 155     0 -> do
 156       -- If the HTTP part barfs, try again after a while.
 157       putStrLn ("Couldn't retrieve " ++ username ++ "'s timeline. Retrying...")
 158       thread_sleep delay
 159       get_latest_status_id cfg username
 160     _ -> return (get_max_status_id initial_timeline)
 161
 162
 163
 164 -- | This function wraps two steps. First, we need to find the latest
 165 --   status id posted by username. Once we have that, we can begin the
 166 --   recursive loop that checks for updates forever. The message
 167 --   argument is optional and is passed to recurse in case the updates
 168 --   should be emailed.
 169 run :: Cfg -> Maybe Message -> String -> IO ()
 170 run cfg msg username = do
 171   latest_status_id <- get_latest_status_id cfg username
 172   recurse cfg username latest_status_id msg
 173   return ()
 174
 175
 176
 177 -- | Take advantage of the Maybe monad to only return a message when
 178 --   we have both a "to" and "from" address.
 179 construct_message :: Cfg -> Maybe Message
 180 construct_message cfg = do
 181   to_addr <- to_address cfg
 182   from_addr <- from_address cfg
 183   return $ make_msg to_addr from_addr
 184   where
 185     make_msg t f = Message { headers = default_headers,
 186                              body = "",
 187                              subject = "",
 188                              to = t,
 189                              from = f }
 190
 191 -- |The main function just parses the command-line arguments and then
 192 -- forks off calls to 'run' for each supplied username. After
 193 -- forking, main loops forever.
 194 main :: IO ()
 195 main = do
 196   -- And a Cfg object.
 197   rc_cfg  <- OC.from_rc
 198   cmd_cfg <- apply_args
 199
 200   -- Merge the config file options with the command-line ones,
 201   -- prefering the command-line ones.
 202   let opt_config = rc_cfg <> cmd_cfg
 203
 204   -- Finally, update a default config with any options that have been
 205   -- set in either the config file or on the command-line.
 206   let cfg = merge_optional default_config opt_config
 207
 208   when (null $ get_usernames (usernames cfg)) $ do
 209     hPutStrLn stderr "ERROR: no usernames supplied."
 210     _ <- show_help
 211     exitWith (ExitFailure exit_no_usernames)
 212
 213   -- If we have both a "To" and "From" address, we'll create a
 214   -- message object to be passed to all of our threads.
 215   let message = construct_message cfg
 216
 217   -- Execute run on each username in a new thread.
 218   let run_curried = run cfg message
 219   _ <- mapM (forkIO . run_curried) (get_usernames (usernames cfg))
 220
 221   _ <- forever $
 222     -- This thread (the one executing main) doesn't do anything,
 223     -- but when it terminates, so do all the threads we forked.
 224     -- As a result, we need to keep this thread on life support.
 225     thread_sleep (heartbeat cfg)
 226
 227   return ()