src/Twitter/Http.hs

   1 module Twitter.Http
   2 where
   3
   4 import Network.Curl
   5 import System.IO (hPutStrLn, stderr)
   6
   7 -- |The API URL of username's timeline.
   8 --
   9 -- See,
  10 --
  11 --   <http://dev.twitter.com/doc/get/statuses/user_timeline>
  12 --
  13 user_timeline_url :: String -> String
  14 user_timeline_url username =
  15     concat [ "http://api.twitter.com/1/statuses/user_timeline.xml",
  16              "?screen_name=" ++ username,
  17              "&include_rts=true",
  18              "&count=10" ]
  19
  20 status_url :: Integer -> String
  21 status_url status_id =
  22     concat [ "http://api.twitter.com/1/statuses/show/",
  23              (show status_id),
  24              ".xml" ]
  25
  26 -- |Given username's last status id, constructs the API URL for
  27 -- username's new statuses. Essentially, 'user_timeline_url' with a
  28 -- "since_id" parameter tacked on.
  29 user_new_statuses_url :: String -> Integer -> String
  30 user_new_statuses_url username last_status_id =
  31     concat [ user_timeline_url username,
  32              "&since_id=" ++ (show last_status_id) ]
  33
  34
  35 get_status :: Integer -> IO (Maybe String)
  36 get_status status_id = do
  37     let uri = (status_url status_id)
  38     status <- (http_get uri)
  39     return status
  40
  41
  42 -- |Return's username's timeline, or 'Nothing' if there was an error.
  43 get_user_timeline :: String -> IO (Maybe String)
  44 get_user_timeline username = do
  45   let uri = (user_timeline_url username)
  46   timeline <- (http_get uri)
  47   return timeline
  48
  49
  50 -- | Returns the XML representing all of username's statuses that are
  51 --   newer than last_status_id.
  52 get_user_new_statuses :: String -> Integer -> IO (Maybe String)
  53 get_user_new_statuses username last_status_id = do
  54   let uri = (user_new_statuses_url username last_status_id)
  55   new_statuses <- (http_get uri)
  56   return new_statuses
  57
  58
  59 -- | Options that will be passed to every curl request.
  60 curl_options :: [CurlOption]
  61 curl_options =
  62   [ CurlTimeout 45,
  63     -- The Global cache is not thread-friendly.
  64     CurlDNSUseGlobalCache False,
  65      -- And we don't want to use a DNS cache anyway.
  66     CurlDNSCacheTimeout 0 ]
  67
  68
  69 -- | Uses the CURL API to retrieve uri. Returns 'Nothing' if there was
  70 --   an error.
  71 http_get :: String -> IO (Maybe String)
  72 http_get uri =
  73   withCurlDo $ do
  74   -- Create a Curl instance.
  75   curl <- initialize
  76
  77   -- Perform the request, and get back a CurlResponse object.
  78   -- The cast is needed to specify how we would like our headers
  79   -- and body returned (Strings).
  80   resp <- do_curl_ curl uri curl_options :: IO CurlResponse
  81
  82   -- Pull out the response code as a CurlCode.
  83   let code = respCurlCode resp
  84
  85   case code of
  86     CurlOK -> return $ Just (respBody resp)
  87     error_code -> do
  88       hPutStrLn stderr ("HTTP Error: " ++ (show error_code))
  89       -- If an error occurred, we want to dump as much information as
  90       -- possible. If this becomes a problem, we can use respGetInfo to
  91       -- query the response object for more information
  92       return Nothing