FriendOrFollow.scala

import java.net.{Authenticator, PasswordAuthentication}
import java.net.{URL, HttpURLConnection}
import scala.xml.{XML, Node}
import scala.collection.mutable.Map

class FriendOrFollow (screen_name:String) {

  private val friends_url = "http://twitter.com/statuses/friends/%s.xml"
  lazy val friends:Map[String, Node] =
    getMap(friends_url.replace("%s", screen_name))

  private val followers_url = "http://twitter.com/statuses/followers/%s.xml"
  lazy val followers:Map[String, Node] =
    getMap(followers_url.replace("%s", screen_name))

  // intersection of sets of friends and followers users.
  lazy val friendsandfollowers = friends.keySet ** followers.keySet

  lazy val not_following_me_back:Map[String, Node] =
    friends.clone -- friendsandfollowers.elements

  lazy val not_following_them_back:Map[String, Node] =
    followers.clone -- friendsandfollowers.elements

  private final def getMap(url:String):Map[String, Node] = {

    def page(n:Int, map:Map[String, Node]):Map[String, Node] = {
      var urlConn = new URL(url+"?page="+n).openConnection match {
        case con:HttpURLConnection => {
          con.connect();
          con.getResponseCode match {
            case 200 => { }
            case _ => { }
          }
          con
        }
      }

      val size=map.size

      (XML.load(urlConn.getInputStream) \\ "user").foldLeft(map){
        (m, user)=> m + ((user \ "id" text) -> user)
      }
      match {
        case _map if(_map.size<=size) => map
        case _map => page(n+1, _map);
      }
    }

    page(1, Map.empty[String, Node])
  }
}

object FriendOrFollowTest {
  def main(arg:Array[String])={

    val (screen_name, username, passwd) = (arg(0), arg(1), arg(2))

    Authenticator.setDefault(
      new Authenticator {
        override def getPasswordAuthentication = {
          new PasswordAuthentication(username, passwd.toCharArray);
        }
      }
    )

    val fof = new FriendOrFollow(screen_name)

    println(screen_name+" is following these people, "+
            "but they are not following "+screen_name+" back.")

    fof.not_following_me_back.foreach { case (id, node)=>
      println(node \ "screen_name" text)
    }

    println("These people are following "+screen_name+", "+
            "but "+screen_name+" is not following them back.")

    fof.not_following_them_back.foreach { case (id, node)=>
      println(node \ "screen_name" text)
    }

  }
}