-- It should more or less be a black box, providing Main with only the
-- information it requires.
module CommandLine
-( help_set,
+( heartbeat,
+ help_set,
help_text,
from_email_address,
to_email_address,
-- |A record containing values for all available options.
-data Options = Options { opt_help :: Bool,
+data Options = Options { opt_heartbeat :: Maybe Int,
+ opt_help :: Bool,
opt_from :: Maybe String,
opt_to :: Maybe String }
-- |Constructs an instance of Options, with each of its members set to
-- default values.
default_options :: Options
-default_options = Options { opt_help = False,
+default_options = Options { opt_heartbeat = Just 600,
+ opt_help = False,
opt_from = Nothing,
opt_to = Nothing }
options :: [OptDescr (Options -> IO Options)]
options =
[ Option ['h'][] (NoArg set_help) "Prints this help message.",
+ Option ['n'][] (ReqArg set_heartbeat "heartbeat") "How many seconds to wait between polling.",
Option ['t'][] (ReqArg set_to "email_address") "Send tweets TO email_address.",
Option ['f'][] (ReqArg set_from "email_address") "Send tweets FROM email_address."
]
+-- | Attempt to parse an 'Int' from a 'String'. This is just a 'Maybe'
+-- wrapper around 'reads'.
+parse_int :: String -> Maybe Int
+parse_int s =
+ case (reads s) of
+ [(n,_)] -> Just n
+ _ -> Nothing
+
+set_heartbeat :: String -> Options -> IO Options
+set_heartbeat arg opts = do
+ let new_heartbeat = parse_int arg
+ return opts { opt_heartbeat = new_heartbeat }
+
set_help :: Options -> IO Options
set_help opts = do
return opts { opt_help = True }
-- The usage header.
usage :: String
-usage = "Usage: twat [-t to_address] [-f from_address] <username1> [username2, [username3]...]"
+usage = "Usage: twat [-n heartbeat] [-t to_address] [-f from_address] <username1> [username2, [username3]...]"
-- The usage header, and all available flags (as generated by GetOpt)
return opts
+-- | A list of parse errors relating to the heartbeat.
+heartbeat_errors :: IO [String]
+heartbeat_errors = do
+ hb <- heartbeat
+ if (isNothing hb)
+ then return ["\"heartbeat\" does not appear to be an integer."]
+ else return []
+
-- |Parse errors relating to the list of usernames.
username_errors :: IO [String]
username_errors = do
let (_, usernames, _) = getOpt Permute options argv
if (null usernames)
- then return ["No usernames provided."]
+ then return ["no usernames provided."]
else return []
toaddr <- to_email_address
fromaddr <- from_email_address
if (isNothing toaddr) && (isJust fromaddr)
- then return ["\"From\" address specified without \"To\" address."]
+ then return ["\"from\" address specified without \"to\" address."]
else return []
toaddr <- to_email_address
fromaddr <- from_email_address
if (isJust toaddr) && (isNothing fromaddr)
- then return ["\"To\" address specified without \"From\" address."]
+ then return ["\"to\" address specified without \"from\" address."]
else return []
parse_errors = do
argv <- getArgs
let (_, _, errors) = getOpt Permute options argv
+ errs_heartbeat <- heartbeat_errors
errs_username <- username_errors
errs_to <- to_errors
errs_from <- from_errors
- return $ map format_error (errors ++ errs_username ++ errs_to ++ errs_from)
+ return $ map format_error (errors ++
+ errs_heartbeat ++
+ errs_username ++
+ errs_to ++
+ errs_from)
-- |Was the "help" option passed on the command line?
help_set :: IO Bool
opts <- parse_options
return (opt_help opts)
+-- |What's the heartbeat?
+heartbeat :: IO (Maybe Int)
+heartbeat = do
+ opts <- parse_options
+ return (opt_heartbeat opts)
-- |What "To" address was given on the command line?
to_email_address :: IO (Maybe String)