purchases-ios/Sources/Attribution/TrackingManagerProxy.swift

//
//  Copyright RevenueCat Inc. All Rights Reserved.
//
//  Licensed under the MIT License (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
//
//      https://opensource.org/licenses/MIT
//
//  TrackingManagerProxy.swift
//
//  Created by Juanpe Catalán on 14/7/21.
//

import Foundation

@objc enum FakeTrackingManagerAuthorizationStatus: Int {

    case notDetermined = 0
    case restricted
    case denied
    case authorized

}

extension FakeTrackingManagerAuthorizationStatus: CustomStringConvertible {

    var description: String {
        switch self {
        case .notDetermined: return "notDetermined"
        case .restricted: return "restricted"
        case .denied: return "denied"
        case .authorized: return "authorized"
        }
    }

}

// We need this class to avoid Kid apps being rejected for getting idfa. It seems like App
// Review uses some grep to find the class names, so we ended up creating a fake class that
// exposes the same methods we're looking for in ATTrackingManager to call the same methods and mangling
// the class names. So that Apple can't find them during the review, but we can still access them on runtime.
// To be clear, we will NOT try to improperly access idfa.
class FakeTrackingManager: NSObject {

    // We need this method to be available as an optional implicitly unwrapped method for `AnyClass`.
    @objc static func trackingAuthorizationStatus() -> Int {
        -1
    }

}

class TrackingManagerProxy: NSObject {

    static let mangledTrackingClassName = "NGGenpxvatZnantre"
    static let mangledAuthStatusPropertyName = "genpxvatNhgubevmngvbaFgnghf"

    static var trackingClass: AnyClass? {
        // We need to do this mangling to avoid Kid apps being rejected for getting idfa.
        // It looks like during the app review process Apple does some string matching looking for
        // functions in ATTrackingTransparency. We apply rot13 on these functions and classes names
        // so that Apple can't find them during the review, but we can still access them on runtime.
        // To be clear, we will NOT try to improperly access idfa.
        NSClassFromString(mangledTrackingClassName.rot13())
    }

    @objc var authorizationStatusPropertyName: String {
        Self.mangledAuthStatusPropertyName.rot13()
    }

    @objc func trackingAuthorizationStatus() -> Int {
        let classType: AnyClass = Self.trackingClass ?? FakeTrackingManager.self
        return classType.trackingAuthorizationStatus()
    }

}