Github emailer

githubNotifications.hs

import Control.Applicative
import Github.Gists
import Github.Users.Followers
import System.Directory
import Control.Monad
import qualified Data.Set as S
import Text.Printf
import System.Process
import System.IO.Unsafe

followersFile = "followers.txt"

compareFollowers Nothing _ = return ()

compareFollowers (Just prev) cur = do
    let newFollowers = S.toList $ cur S.\\ prev
        unfollowedBy = S.toList $ prev S.\\ cur
    forM_ newFollowers $ \userName ->
        system (printf "echo 'https://www.github.com/%s' | mail -s '%s followed you on Github!' bluemangroupie@gmail.com" userName userName)
    forM_ unfollowedBy $ \userName ->
        system (printf "echo 'https://www.github.com/%s' | mail -s '%s unfollowed you on Github!' bluemangroupie@gmail.com" userName userName)

main = do
    followers_ <- usersFollowing "egonSchiele"
    fileExists <- doesFileExist followersFile
    let prevFollowers = if fileExists
                          then Just (S.fromList . lines . unsafePerformIO . readFile $ followersFile)
                          else Nothing

    case followers_ of
      Left err -> print err
      Right followers -> do
        let logins = githubOwnerLogin <$> followers
        compareFollowers prevFollowers (S.fromList logins)
        writeFile followersFile (unlines logins)