FacebookAuth.swift

import Foundation
import FBSDKCoreKit
import FBSDKLoginKit

class FacebookAuth {

  class func auth(callback: (Bool) -> (), viewController: UIViewController) {
    
    let parameters = ["fields" : "id,name,email"]
    let facebookReadPermissions = ["public_profile", "email", "user_friends"]

    if FBSDKAccessToken.currentAccessToken() != nil {
      FBSDKAccessToken.refreshCurrentAccessToken { (connection, result, error) -> Void in

        let graphRequest : FBSDKGraphRequest = FBSDKGraphRequest(graphPath: "me", parameters: parameters)
        graphRequest.startWithCompletionHandler { (connection, result, error) -> Void in
          if error != nil {
            FBSDKLoginManager().logOut()
            callback(false)
          } else if result != nil {
            validateUserData(callback, result: result)
            return
          } else {
            callback(false)
          }
        }
      }
      
    }
    
    FBSDKLoginManager().logInWithReadPermissions(facebookReadPermissions, fromViewController: viewController, handler: {
      (result:FBSDKLoginManagerLoginResult!, error:NSError!) -> Void in
      if error != nil {
        FBSDKLoginManager().logOut()
        callback(false)
        return
      } else if result != nil && result.isCancelled {
        FBSDKLoginManager().logOut()
        callback(false)
        return
      } else {
        let graphRequest : FBSDKGraphRequest = FBSDKGraphRequest(graphPath: "me", parameters: parameters)
        graphRequest.startWithCompletionHandler { (connection, result, error) -> Void in
          if error != nil {
            FBSDKLoginManager().logOut()
            callback(false)
          } else if result != nil {
            validateUserData(callback, result: result)
          }
        }
      }
    })
    
  }
  
  class func validateUserData(callback: (Bool) -> (), result : AnyObject?) {
    if let userData = result as? [String:AnyObject] {
      if userData.count > 0 {
        analyseLogin(callback,
          name: (userData["name"] as? String)!,
          email: (userData["email"] as? String)!,
          facebookId: (userData["id"] as? String)!)
      } else {
        callback(false)
      }
    } else {
      callback(false)
    }
  }
  
  class func analyseLogin(callback: (Bool) -> (), name: String, email: String, facebookId: String) {
    //Request for our web service, no points to be verified here.
  }
  
}