//
//  Inception.swift
//  PrivadoVPN
//
//  Created by Juraldinio on 8/18/20.
//  Copyright © 2020 Privado LLC. All rights reserved.
//

import Foundation

final class Inception {
    
    private enum Constants {
        static let authenticate = "auth"
        static let customer = "customer"
        //
        static let suffixLength = 5
    }
    
    // Credentials passed from url
    private struct Credentials: Decodable {
        let user: String
        let pass: String
    }
    // privadovpn://auth?yLCUMSNr2bQ5Vq-38Hhw16RhwVGCgMM1ETsYzEXd0P8GBaUGnS65HSfB0Nkm9bz1vQcDw

    static func handle(url: URL) -> Route? {
        
        guard let scheme = url.scheme
              , scheme.localizedCaseInsensitiveCompare(PrivadoConstants.Application.scheme) == .orderedSame
              , let host = url.host else { return nil }
        
        switch host {
        case Constants.authenticate:
            return Self.authenticate(components: URLComponents(url: url, resolvingAgainstBaseURL: false))
        case Constants.customer:
            return .customer
        default:
            return nil
        }
        
        /*let encoded = host.replacingOccurrences(of: base64, with: "")
        guard let data = Data(base64Encoded: encoded)
            , let credentials = try? JSONDecoder().decode(Credentials.self, from: data) else {
                return nil
        }
        
        return .login(type: .authenticate(credentials.user, credentials.pass))*/
    }
    
    // MARK: - Static Private
    
    private static func authenticate(components: URLComponents?) -> Route? {
        
        guard let components = components
              , let urlToken = components.queryItems?.first?.name else { return nil }
        
        let token = urlToken
            .replacingOccurrences(of: "-", with: "+")
            .replacingOccurrences(of: "_", with: "/")
    
        guard let encrToken = Data(base64Encoded: String(token.suffix(token.count - Constants.suffixLength)))
              , let key = PrivadoConstants.Session.key.data(using: .utf8) else {
            return nil
        }
        
        let blockSize = 16
        let iv = encrToken.prefix(upTo: blockSize)
        let message = encrToken.suffix(encrToken.count - blockSize)
        
        guard let decriptedToken = CryptoAES(key: key, iv: iv).decrypt(data: message) else { return nil }
        
        let credentials = decriptedToken
            .split(separator: ":")
            .map { String($0) }
        
        if credentials.count == 2
           , let username = credentials.first
           , let password = credentials.last {
            return .login(type: .authenticate(username, password, true))
        }
        
        return nil
        
    }
    
}