ServerSideToken.hs

#!/usr/bin/env stack
-- stack --resolver lts-8.13 --install-ghc runghc --package scotty --package fb
-- --package text --package http-client --package http-client-tls

{-# LANGUAGE OverloadedStrings #-}

import Control.Monad.Trans (lift)
import Control.Monad.Trans.Resource
import qualified Data.Text.Lazy as T
import Facebook
import Network.HTTP.Client
import Network.HTTP.Client.TLS
import Web.Scotty


main = do
  mgr <- newManager tlsManagerSettings

  scotty 3000 $ do
    get "/" $ do
      url <- runResourceT $ runFacebookT credentials mgr $ do
        getUserAccessTokenStep1 callbackUrl scopes
      redirect $ T.fromStrict url

    get "/auth/facebook/callback" $ do
      code <- param "code"
      token <- lift $ runResourceT $ runFacebookT credentials mgr $ do
        getUserAccessTokenStep2 callbackUrl [("code", code)]
      redirect "/"


callbackUrl = "http://localhost:3000/auth/facebook/callback"


credentials = Credentials
  { appName = "xxx"
  , appId = "xxx"
  , appSecret = "xxx" }


scopes =
  [ "public_profile"
  , "email"
  , "manage_pages"
  ]