htsn-0.0.4: src/Main.hs
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE DoAndIfThenElse #-}
module Main
where
import Control.Concurrent ( threadDelay )
import Control.Exception ( bracket, throw )
import Control.Monad ( when )
import Data.List ( isPrefixOf )
import Data.Maybe ( isNothing )
import Data.Monoid ( (<>) )
import Network (
connectTo,
PortID (PortNumber) )
import System.Console.CmdArgs ( def )
import System.Directory ( doesFileExist )
import System.Exit ( ExitCode(..), exitWith )
import System.FilePath ( (</>) )
import System.IO (
BufferMode (NoBuffering),
Handle,
hClose,
hGetChar,
hGetLine,
hPutStr,
hSetBuffering,
stderr,
stdout )
import System.IO.Error ( catchIOError )
import System.Timeout ( timeout )
import CommandLine ( get_args )
import Configuration ( Configuration(..), merge_optional )
import ExitCodes (
exit_no_feed_hosts,
exit_no_password,
exit_no_username,
exit_pidfile_exists )
import FeedHosts ( FeedHosts(..) )
import Network.Services.TSN.Logging ( init_logging )
import qualified OptionalConfiguration as OC (
OptionalConfiguration(..),
from_rc )
import Network.Services.TSN.Report (
report_debug,
report_info,
report_warning,
report_error )
import Network.Services.TSN.Terminal ( display_sent )
import Xml ( parse_xmlfid )
import Unix ( full_daemonize )
-- | Receive a single line of text from a Handle, and send it to the
-- debug log.
--
recv_line :: Handle -> IO String
recv_line h = do
line <- hGetLine h
report_debug (line ++ "\n")
return line
-- | Takes a Configuration, and an XML document (as a String). The XML
-- document is written to the output directory, as specified by the
-- Configuration.
--
-- This can fail, but we don't purposefully throw any exceptions. If
-- something goes wrong, we would rather log it and keep going.
--
save_document :: Configuration -> String -> IO ()
save_document cfg doc =
case either_path of
Left err -> report_error err
Right path -> do
already_exists <- doesFileExist path
when already_exists $ do
let msg = "File " ++ path ++ " already exists, overwriting."
report_warning msg
writeFile path doc
report_info $ "Wrote file: " ++ path ++ "."
where
-- All the fmaps are because we're working inside a Maybe.
xmlfid = fmap show (parse_xmlfid doc)
filename = fmap (++ ".xml") xmlfid
either_path = fmap ((output_directory cfg) </>) filename
-- | Loop forever, writing the buffer to file whenever a </message>
-- tag is seen. This is the low-level "loop forever" function that
-- we stay in as long as we are connected to one feed.
--
-- The documentation at
-- <http://www.sportsnetworkdata.com/feeds/xml-levels.asp> states
-- that \<message\> will always be the root element of the XML
-- documents, and \</message\> will be the final line transmitted
-- for a given document. We therefore rely on this to simplify
-- processing.
--
loop :: Configuration -> Handle -> [String] -> IO ()
loop !cfg !h !buffer = do
line <- recv_line h
let new_buffer = line : buffer
-- Use isPrefixOf to avoid line-ending issues. Hopefully they won't
-- send invalid junk (on the same line) after closing the root
-- element.
if "</message>" `isPrefixOf` line
then do
-- The buffer is in reverse (newest first) order, though, so we
-- have to reverse it first. We then concatenate all of its lines
-- into one big string.
let document = concat $ reverse new_buffer
save_document cfg document
loop cfg h [] -- Empty the buffer before looping again.
else
-- Append line to the head of the buffer and loop.
loop cfg h new_buffer
-- | Once we're connected to a feed, we need to log in. There's no
-- protocol for this (the docs don't mention one), but we have
-- (apparently) successfully guessed it.
--
-- The first thing TSN sends once we've connected is the string
-- "Username: ", containing 10 ASCII characters. We then send a
-- username, followed by a newline. If TSN likes the username, the
-- second they'll send is the string "Password: ", also containing
-- 10 ASCII characters, to which we reply in kind.
--
-- Assuming the above will always hold, it is implemented as follows:
--
-- 1. Receive 10 chars
--
-- 2. Send username if we got the username prompt
--
-- 3. Receive 10 chars
--
-- 4. Send password if we got the password prompt
--
-- If TSN likes the password as well, they send the string "The
-- Sports Network" before finally beginning to stream the feed.
--
log_in :: Configuration -> Handle -> IO ()
log_in cfg h = do
prompt1 <- recv_prompt h
if prompt1 /= username_prompt then
report_error "Didn't receive username prompt."
else do
send_cred h (username cfg)
prompt2 <- recv_prompt h
if prompt2 /= password_prompt then
report_error "Didn't receive password prompt."
else do
send_cred h (password cfg)
_ <- recv_line h -- "The Sports Network"
report_info $ "Logged in as " ++ (username cfg) ++ "."
return ()
where
username_prompt = "Username: "
password_prompt = "Password: "
send_cred :: Handle -> String -> IO ()
send_cred h' s = do
-- The carriage return is super important!
let line = s ++ "\r\n"
hPutStr h' line
display_sent line -- Don't log the username/password!
recv_chars :: Int -> Handle -> IO String
recv_chars n h' = do
s <- sequence [ hGetChar h' | _ <- [1..n] ]
report_debug s
return s
recv_prompt :: Handle -> IO String
recv_prompt = recv_chars 10
-- | Connect to @host@ and attempt to parse the feed. As long as we
-- stay connected and nothing bad happens, the program will remain in
-- this function. If anything goes wrong, then the current invocation
-- of connect_and_parse will return, and get called again later
-- (probably with a different @host@).
--
-- Steps:
--
-- 1. Connect to the host on the XML port
--
-- 2. Log in
--
-- 3. Go into the eternal read/save loop.
--
connect_and_parse :: Configuration -> String -> IO ()
connect_and_parse cfg host = do
report_info $ "Connecting to " ++ host ++ "."
bracket acquire_handle release_handle action
return ()
where
five_seconds :: Int
five_seconds = 5000000
acquire_handle = connectTo host (PortNumber 4500)
release_handle = hClose
action h = do
-- No buffering anywhere.
hSetBuffering h NoBuffering
-- The feed is often unresponsive after we send out username. It
-- happens in a telnet session, too (albeit less frequently?),
-- so there might be a bug on their end.
--
-- If we dump the packets with tcpdump, it looks like their
-- software is getting confused: they send us some XML in
-- the middle of the log-in procedure.
--
-- On the other hand, the documentation at
-- <http://www.sportsnetworkdata.com/feeds/xml-levels.asp>
-- states that you can only make one connection per username to
-- a given host. So maybe they're simply rejecting the username
-- in an unfriendly fashion. In any case, the easiest fix is to
-- disconnect and try again.
--
login_worked <- timeout five_seconds $ log_in cfg h
case login_worked of
Nothing -> report_info $ "Login timed out (5 seconds). "
++ "Waiting 5 seconds to reconnect."
Just _ -> loop cfg h []
-- | A wrapper around threadDelay which takes seconds instead of
-- microseconds as its argument.
--
thread_sleep :: Int -> IO ()
thread_sleep seconds = do
let microseconds = seconds * (10 ^ (6 :: Int))
threadDelay microseconds
-- | The entry point of the program.
--
main :: IO ()
main = do
rc_cfg <- OC.from_rc
cmd_cfg <- get_args
-- Merge the config file options with the command-line ones,
-- prefering the command-line ones.
let opt_config = rc_cfg <> cmd_cfg
-- Update a default config with any options that have been set in
-- either the config file or on the command-line. We initialize
-- logging before the missing parameter checks below so that we can
-- log the errors.
let cfg = (def :: Configuration) `merge_optional` opt_config
init_logging (log_level cfg) (log_file cfg) (syslog cfg)
-- Check the optional config for missing required options. This is
-- necessary because if the user specifies an empty list of
-- hostnames in e.g. the config file, we want to bail rather than
-- fall back on the default list (which was merged from a default
-- Configuration above).
when (null $ get_feed_hosts (OC.feed_hosts opt_config)) $ do
report_error "No feed hosts supplied."
exitWith (ExitFailure exit_no_feed_hosts)
when (isNothing (OC.password opt_config)) $ do
report_error "No password supplied."
exitWith (ExitFailure exit_no_password)
when (isNothing (OC.username opt_config)) $ do
report_error "No username supplied."
exitWith (ExitFailure exit_no_username)
when (daemonize cfg) $ do
-- Old PID files can be left around after an unclean shutdown. We
-- only care if we're running as a daemon.
pidfile_exists <- doesFileExist (pidfile cfg)
when pidfile_exists $ do
report_error $ "PID file " ++ (pidfile cfg) ++ " already exists. "
++ "Refusing to start."
exitWith (ExitFailure exit_pidfile_exists)
-- This may be superstition (and I believe stderr is unbuffered),
-- but it can't hurt.
hSetBuffering stderr NoBuffering
hSetBuffering stdout NoBuffering
-- The rest of the program is kicked off by the following line which
-- begins connecting to our feed hosts, starting with the first one,
-- and proceeds in a round-robin fashion.
let run_program = round_robin cfg 0
-- If we were asked to daemonize, do that; otherwise just run the thing.
if (daemonize cfg)
then try_daemonize cfg run_program
else run_program
where
-- | This is the top-level "loop forever" function. If an
-- exception is thrown, it will propagate up to this point, where
-- it will be logged and ignored in style.
--
-- Afterwards, we recurse (call ourself) again to loop more forevers.
--
round_robin :: Configuration -> Int -> IO ()
round_robin cfg feed_host_idx = do
let hosts = get_feed_hosts $ feed_hosts cfg
let host = hosts !! feed_host_idx
catchIOError (connect_and_parse cfg host) (report_error . show)
thread_sleep 5 -- Wait 5s before attempting to reconnect.
round_robin cfg $ (feed_host_idx + 1) `mod` (length hosts)
-- | A exception handler around full_daemonize. If full_daemonize
-- doesn't work, we report the error and crash. This is fine; we
-- only need the program to be resilient once it actually starts.
--
try_daemonize :: Configuration -> IO () -> IO ()
try_daemonize cfg program =
catchIOError
(full_daemonize cfg program)
(\e -> do
report_error (show e)
throw e)