-- | Functions and data for working with Twitter users.
module Twitter.User (
  User(..),
  screen_name_to_timeline_url )
where

import Control.Applicative ( (<$>) )
import Data.Aeson ( (.:), FromJSON(..), Value(Object) )
import Data.Text ( pack )
import Data.Monoid ( mempty )


-- | Represents a Twitter user, and contains the only attribute
--   thereof that we care about: the screen (user) name.
--
data User = User { screen_name :: String } deriving (Eq, Show)

instance FromJSON User where
  -- | Parse the JSON we get from the Twitter API into a 'User' if we
  --   can.
  --
  parseJSON (Object u) =
    User <$> (u .: screen_name_field)
    where
      screen_name_field = pack "screen_name"

  -- Do whatever.
  parseJSON _ = mempty


-- | Get the URL for the given screen name's timeline.
--
--   Examples:
--
--   >>> screen_name_to_timeline_url "washington_irving"
--   "http://twitter.com/washington_irving"
--
screen_name_to_timeline_url :: String -> String
screen_name_to_timeline_url =
  ("http://twitter.com/" ++)