//
//  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 {
        
        // Hosts launching the app with url
        static let auth = "auth"
        static let purchaseList = "purchase_list"
    }
    
    // Credentials passed from url
    private struct Credentials: Decodable {
        let user: String
        let pass: String
    }
    
    static func handle(url: URL) -> Route? {
        
        guard let scheme = url.scheme,
              scheme.localizedCaseInsensitiveCompare(PrivadoConstants.Application.urlScheme) == .orderedSame,
              let host = url.host else { return nil }
        
        switch host {
        case Constants.auth:
            if let token = URLComponents(url: url, resolvingAgainstBaseURL: false)?.queryItems?.first?.name {
                return Self.authenticate(urlToken: token)
            }
        case Constants.purchaseList:
            return .preference(tab: .upgrade)
        default:
            break
        }
        
        return nil
    }
    
    static func authenticate(urlToken: String) -> Route? {
        
        let token = urlToken
            .replacingOccurrences(of: "-", with: "+")
            .replacingOccurrences(of: "_", with: "/")
    
        guard let encrToken = Data(base64Encoded: String(token.suffix(token.count - 5)))
              , 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 decrToken = CryptoAES(key: key, iv: iv).decrypt(data: message) else {
            return nil
        }
        
        let credentials = decrToken.split(separator: ":").map { String($0) }
        if credentials.count == 2
           , let username = credentials.first
           , let password = credentials.last {
            return .login(type: .authenticate(username, password))
        }
        return nil
    }
}