{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE FlexibleContexts #-}

-- Example:
--   $ export OAUTH_CONSUMER_KEY="your consumer key"
--   $ export OAUTH_CONSUMER_SECRET="your consumer secret"
--   $ runhaskell oauth_pin.hs

module Main where

import Web.Twitter.Conduit hiding (lookup)
import Web.Authenticate.OAuth as OA
import Network.HTTP.Conduit
import qualified Data.ByteString.Char8 as S8
import Data.Maybe
import Data.Monoid
import Control.Monad.Trans.Control
import Control.Monad.Trans.Resource
import Control.Monad.IO.Class
import System.Environment
import System.IO (hFlush, stdout)

getTokens :: IO OAuth
getTokens = do
    consumerKey <- getEnv "OAUTH_CONSUMER_KEY"
    consumerSecret <- getEnv "OAUTH_CONSUMER_SECRET"
    return $
        twitterOAuth
        { oauthConsumerKey = S8.pack consumerKey
        , oauthConsumerSecret = S8.pack consumerSecret
        , oauthCallback = Just "oob"
        }

authorize :: (MonadBaseControl IO m, MonadResource m)
          => OAuth -- ^ OAuth Consumer key and secret
          -> Manager
          -> m Credential
authorize oauth mgr = do
    cred <- OA.getTemporaryCredential oauth mgr
    let url = OA.authorizeUrl oauth cred
    pin <- getPIN url
    OA.getAccessToken oauth (OA.insert "oauth_verifier" pin cred) mgr
  where
    getPIN url = liftIO $ do
        putStrLn $ "browse URL: " ++ url
        putStr "> what was the PIN twitter provided you with? "
        hFlush stdout
        S8.getLine

main :: IO ()
main = do
    tokens <- getTokens
    Credential cred <- liftIO $ withManager $ authorize tokens
    print cred

    S8.putStrLn . S8.intercalate "\n" $
        [ "export OAUTH_CONSUMER_KEY=\"" <> oauthConsumerKey tokens <> "\""
        , "export OAUTH_CONSUMER_SECRET=\"" <> oauthConsumerSecret tokens <> "\""
        , "export OAUTH_ACCESS_TOKEN=\"" <> fromMaybe "" (lookup "oauth_token" cred) <> "\""
        , "export OAUTH_ACCESS_SECRET=\"" <> fromMaybe "" (lookup "oauth_token_secret" cred) <> "\""
        ]