InstagramQuerier.swift

import UIKit
import AFNetworking

class InstagramQuerier: NSObject {
    static let sharedQuerier = InstagramQuerier()
    private let manager : AFHTTPRequestOperationManager = AFHTTPRequestOperationManager()
    
  func fetchFollowers(account: Account, count: Int = -1, completion: (Bool, [User]) -> (Void)) {
        let params = "/users/\(account.userId)/followed-by|access_token=\(account.accessToken)"
        let sig = HMAC.signWithKey(UserSettings.InstagramClientSecret(), usingData: params)
        let parameters = [
            "access_token" : account.accessToken,
            "sig" : sig
        ]
        let urlString = "https://api.instagram.com/v1/users/\(account.userId)/followed-by/"
        manager.GET(urlString, parameters: parameters, success: { (operation, result) -> Void in
            let result = result as! NSDictionary
            let pagination = result["pagination"] as! NSDictionary
            let nextURLString = pagination["next_url"] as? String
            
            let usersInfo = result["data"] as! NSArray
            let currentFollowers = User.parse(usersInfo)
            self.followersHelper(count, currentFollowers: currentFollowers, nextURLString: nextURLString, completion: completion)
            }) { (operation, error) -> Void in
                completion(false, [])
        }
    }
    
    private func followersHelper(count: Int, currentFollowers: [User], nextURLString: String?, completion: (Bool, [User]) -> (Void)) {
        if let nextURLString = nextURLString {
            
            let nextURL = NSURL(string: nextURLString)!
            let queryStrings = nextURL.parameters()
            let accessToken = queryStrings["access_token"]!
            let cursor = queryStrings["cursor"]!
            let userId = nextURL.pathComponents![3]
            let params = "/users/\(userId)/followed-by|access_token=\(accessToken)|cursor=\(cursor)"
            let sig = HMAC.signWithKey(UserSettings.InstagramClientSecret(), usingData: params)
            let parameters = [
                "access_token" : accessToken,
                "cursor" : cursor,
                "sig" : sig
            ]
            
            manager.GET("https://api.instagram.com/v1/users/\(userId)/followed-by/", parameters: parameters, success: { (operation, result) -> Void in
                let result = result as! NSDictionary
                let pagination = result["pagination"] as! NSDictionary
                let nextURLString = pagination["next_url"] as? String
                
                let usersInfo = result["data"] as! NSArray
                let users = User.parse(usersInfo)
                
                let currentFollowers = currentFollowers + users
                
                if currentFollowers.count >= count && count != -1 {
                    completion(true, currentFollowers)
                } else {
                    self.followersHelper(count, currentFollowers: currentFollowers, nextURLString: nextURLString, completion: completion)
                }
                }) { (operation, error) -> Void in
                    
            }
        } else {
            completion(true, currentFollowers)
        }
    }
}