oAuth2 as Grails Controller

gistfile1.txt

import grails.converters.JSON

class AuthController {

    def login = {
      //let's fetch everything which depends on the provider from the config
      def config    = grailsApplication.config.oauth.providers[params.provider]
      def appKey    = config.appKey
      def secret    = config.secret
      def scope     = config.scope
      def callback  = g.createLink(action:'callback',absolute:true)
      def state     = params.provider+":"+new Sha256Hash("3r89sd"+new Date()+Math.random()).toHex()
      def url       = config.url+"&scope=${->scope.encodeAsURL()}&redirect_uri=${->callback.encodeAsURL()}&state=${->state}&client_id=${->appKey.encodeAsURL()}"
      session.state = state
      redirect  url:url
    }
    def callback() {
        println params
        //verify cross site forgery
        if (params.state!=session.state) {
            throw Exception("something nasty happened...")
        }
        def provider   = params.state.split(':')[0]
        def config     = grailsApplication.config.oauth.providers[provider]
        def appKey     = config.appKey
        def secret     = config.secret
        def scope      = config.scope
        def tokenUrl   = config.tokenUrl
        def state      = session.state
        def callback   = g.createLink(action:'callback',absolute:true)
        def tokenQuery = "code=${->params.code.encodeAsURL()}&client_id=${->appKey.encodeAsURL()}&client_secret=${->secret.encodeAsURL()}&redirect_uri=${->callback.encodeAsURL()}&grant_type=authorization_code"
        def url        = new URL(tokenUrl)
        def connection = url.openConnection()
        connection.setRequestMethod("POST")
        connection.doOutput = true

        def writer = new OutputStreamWriter(connection.outputStream)
        writer.write(tokenQuery)
        writer.flush()
        writer.close()
        connection.connect()
        def body = connection.content.text
        def response = JSON.parse(body)
        if (response.size()==0) {
            //for facebook, we get no JSON but URL params
            body.split('&').inject([:]) {map, kv ->
                def (key, value) = kv.split('=').toList()
                if(value != null) {
                    response[key] = URLDecoder.decode(value)
                }
            }        
        }
        def userinfo = config.identityApi+"?access_token=${->response.access_token}"
        def profile = JSON.parse(new URL(userinfo).text)
        def name    = profile.name
        def email   = profile.email?:profile.emails?.preferred
    }

}