src/CommandLine.hs

   1 -- |The CommandLine module handles parsing of the command-line options.
   2 -- It should more or less be a black box, providing Main with only the
   3 -- information it requires.
   4 module CommandLine
   5 ( heartbeat,
   6   help_set,
   7   help_text,
   8   ignore_replies_set,
   9   ignore_retweets_set,
  10   from_email_address,
  11   to_email_address,
  12   parse_errors,
  13   parse_usernames
  14 ) where
  15
  16 import Data.Maybe (isJust, isNothing)
  17 import System.Console.GetOpt
  18 import System.Environment (getArgs)
  19
  20
  21
  22 -- |A record containing values for all available options.
  23 data Options = Options { opt_heartbeat :: Maybe Int,
  24                          opt_help  :: Bool,
  25                          opt_ignore_replies :: Bool,
  26                          opt_ignore_retweets :: Bool,
  27                          opt_from :: Maybe String,
  28                          opt_to :: Maybe String }
  29
  30
  31 -- |Constructs an instance of Options, with each of its members set to
  32 -- default values.
  33 default_options :: Options
  34 default_options = Options { opt_heartbeat = Just 600,
  35                             opt_help = False,
  36                             opt_ignore_replies = False,
  37                             opt_ignore_retweets = False,
  38                             opt_from = Nothing,
  39                             opt_to = Nothing }
  40
  41
  42 -- |The options list that we construct associates a function with each
  43 -- option. This function is responsible for updating an Options record
  44 -- with the appropriate value.
  45 --
  46 -- For more information and an example of this idiom, see,
  47 --
  48 -- <http://www.haskell.org/haskellwiki/High-level_option_handling_with_GetOpt>
  49 --
  50 options :: [OptDescr (Options -> IO Options)]
  51 options =
  52   [ Option
  53       ['h']["help"]
  54       (NoArg set_help)
  55       "Prints this help message.",
  56
  57     Option
  58       ['n']["heartbeat"]
  59       (ReqArg set_heartbeat "heartbeat")
  60       "How many seconds to wait between polling.",
  61
  62     Option
  63       ['t']["to"]
  64       (ReqArg set_to "email_address")
  65       "Send tweets TO email_address.",
  66
  67     Option
  68       ['f']["from"]
  69       (ReqArg set_from "email_address")
  70       "Send tweets FROM email_address.",
  71
  72     Option
  73       ['i']["ignore-replies"]
  74       (NoArg set_ignore_replies)
  75       "Ignore replies.",
  76
  77     Option
  78       ['I']["ignore-retweets"]
  79       (NoArg set_ignore_retweets)
  80       "Ignore retweets."
  81   ]
  82
  83
  84 -- | Attempt to parse an 'Int' from a 'String'. This is just a 'Maybe'
  85 --   wrapper around 'reads'.
  86 parse_int :: String -> Maybe Int
  87 parse_int s =
  88   case (reads s) of
  89     [(n,_)]   -> Just n
  90     _         -> Nothing
  91
  92 set_heartbeat :: String -> Options -> IO Options
  93 set_heartbeat arg opts = do
  94   let new_heartbeat = parse_int arg
  95   return opts { opt_heartbeat = new_heartbeat }
  96
  97 set_help :: Options -> IO Options
  98 set_help opts = do
  99   return opts { opt_help = True }
 100
 101 set_ignore_retweets :: Options -> IO Options
 102 set_ignore_retweets opts =
 103   return opts { opt_ignore_retweets = True }
 104
 105 set_ignore_replies :: Options -> IO Options
 106 set_ignore_replies opts =
 107   return opts { opt_ignore_replies = True }
 108
 109 set_to :: String -> Options -> IO Options
 110 set_to arg opts = do
 111   return opts { opt_to = Just arg }
 112
 113 set_from :: String -> Options -> IO Options
 114 set_from arg opts = do
 115   return opts { opt_from = Just arg }
 116
 117
 118 -- The usage header.
 119 usage :: String
 120 usage = "Usage: twat [-n heartbeat] [-t to_address] [-f from_address] <username1> [username2, [username3]...]"
 121
 122
 123 -- The usage header, and all available flags (as generated by GetOpt)
 124 help_text :: String
 125 help_text = usageInfo usage options
 126
 127
 128 -- Return a list of options.
 129 parse_options :: IO Options
 130 parse_options = do
 131   argv <- getArgs
 132   let (actions, _, _) = getOpt Permute options argv
 133
 134   -- This will execute each of the functions contained in our options
 135   -- list, one after another, on a default_options record. The end
 136   -- result should be an Options instance with all of its members set
 137   -- correctly.
 138   opts <- foldl (>>=) (return default_options) actions
 139
 140   return opts
 141
 142
 143 -- | A list of parse errors relating to the heartbeat.
 144 heartbeat_errors :: IO [String]
 145 heartbeat_errors = do
 146   hb <- heartbeat
 147   if (isNothing hb)
 148     then return ["\"heartbeat\" does not appear to be an integer."]
 149     else return []
 150
 151 -- |Parse errors relating to the list of usernames.
 152 username_errors :: IO [String]
 153 username_errors = do
 154   argv <- getArgs
 155   let (_, usernames, _) = getOpt Permute options argv
 156
 157   if (null usernames)
 158     then return ["no usernames provided."]
 159     else return []
 160
 161
 162 -- |Parse errors relating to the "To" address.
 163 to_errors :: IO [String]
 164 to_errors = do
 165   toaddr <- to_email_address
 166   fromaddr <- from_email_address
 167   if (isNothing toaddr) && (isJust fromaddr)
 168     then return ["\"from\" address specified without \"to\" address."]
 169     else return []
 170
 171
 172 -- |Parse errors relating to the "From" address.
 173 from_errors :: IO [String]
 174 from_errors = do
 175   toaddr <- to_email_address
 176   fromaddr <- from_email_address
 177   if (isJust toaddr) && (isNothing fromaddr)
 178     then return ["\"to\" address specified without \"from\" address."]
 179     else return []
 180
 181
 182 -- |Format an error message for printing.
 183 format_error :: String -> String
 184 format_error err = "ERROR: " ++ err ++ "\n"
 185
 186
 187 -- |Return a list of all parse errors.
 188 parse_errors :: IO [String]
 189 parse_errors = do
 190   argv <- getArgs
 191   let (_, _, errors) = getOpt Permute options argv
 192   errs_heartbeat <- heartbeat_errors
 193   errs_username <- username_errors
 194   errs_to <- to_errors
 195   errs_from <- from_errors
 196   return $ map format_error (errors ++
 197                              errs_heartbeat ++
 198                              errs_username ++
 199                              errs_to ++
 200                              errs_from)
 201
 202 -- |Was the "help" option passed on the command line?
 203 help_set :: IO Bool
 204 help_set = do
 205     opts <- parse_options
 206     return (opt_help opts)
 207
 208 -- | Was the "ignore-replies" option passes on the command line?
 209 ignore_replies_set :: IO Bool
 210 ignore_replies_set = do
 211   opts <- parse_options
 212   return (opt_ignore_replies opts)
 213
 214 -- | Was the "ignore-retweets" option passes on the command line?
 215 ignore_retweets_set :: IO Bool
 216 ignore_retweets_set = do
 217   opts <- parse_options
 218   return (opt_ignore_retweets opts)
 219
 220 -- |What's the heartbeat?
 221 heartbeat :: IO (Maybe Int)
 222 heartbeat = do
 223   opts <- parse_options
 224   return (opt_heartbeat opts)
 225
 226 -- |What "To" address was given on the command line?
 227 to_email_address :: IO (Maybe String)
 228 to_email_address = do
 229     opts <- parse_options
 230     return (opt_to opts)
 231
 232 -- |What "From" address was given on the command line?
 233 from_email_address :: IO (Maybe String)
 234 from_email_address = do
 235     opts <- parse_options
 236     return (opt_from opts)
 237
 238
 239 -- |What usernames were passed on the command line?
 240 parse_usernames :: IO [String]
 241 parse_usernames = do
 242   argv <- getArgs
 243   let (_, usernames, _) = getOpt Permute options argv
 244   return usernames