Tusker/Tusker/Screens/Onboarding/OnboardingViewController.swift

//
//  OnboardingViewController.swift
//  Tusker
//
//  Created by Shadowfacts on 8/18/18.
//  Copyright © 2018 Shadowfacts. All rights reserved.
//

import UIKit
import AuthenticationServices
import Pachyderm

protocol OnboardingViewControllerDelegate {
    func didFinishOnboarding(account: LocalData.UserAccountInfo)
}

class OnboardingViewController: UINavigationController {

    static var blocks: [NSRegularExpression] = {
        guard let path = Bundle.main.path(forResource: "DomainBlocks", ofType: "plist"),
            let array = NSArray(contentsOfFile: path) as? [String] else { return [] }
        return array.compactMap { try? NSRegularExpression(pattern: $0, options: .caseInsensitive) }
    }()
    
    var onboardingDelegate: OnboardingViewControllerDelegate?
    
    var instanceSelector = InstanceSelectorTableViewController()
    
    var authenticationSession: ASWebAuthenticationSession?
    
    init() {
        super.init(rootViewController: instanceSelector)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        instanceSelector.delegate = self
    }
    
    private func doAuthenticationSession(url: URL) async throws -> URL {
        return try await withCheckedThrowingContinuation { continuation in
            self.authenticationSession = ASWebAuthenticationSession(url: url, callbackURLScheme: "tusker") { url, error in
                defer {
                    DispatchQueue.main.async {
                        self.authenticationSession = nil
                    }
                }
                if let url = url {
                    continuation.resume(returning: url)
                } else {
                    continuation.resume(throwing: error!)
                }
            }
            DispatchQueue.main.async {
                // Prefer ephemeral sessions to make it easier to sign into multiple accounts on the same instance.
                self.authenticationSession!.prefersEphemeralWebBrowserSession = true
                self.authenticationSession!.presentationContextProvider = self
                self.authenticationSession!.start()
            }
        }
    }

}

extension OnboardingViewController: InstanceSelectorTableViewControllerDelegate {
    func didSelectInstance(url instanceURL: URL) {
        async {
            let mastodonController = MastodonController(instanceURL: instanceURL)
            let (clientID, clientSecret) = await mastodonController.registerApp()
            
            var components = URLComponents(url: instanceURL, resolvingAgainstBaseURL: false)!
            components.path = "/oauth/authorize"
            components.queryItems = [
                URLQueryItem(name: "client_id", value: clientID),
                URLQueryItem(name: "response_type", value: "code"),
                URLQueryItem(name: "scope", value: "read write follow"),
                URLQueryItem(name: "redirect_uri", value: "tusker://oauth")
            ]
            
            guard let url = try? await self.doAuthenticationSession(url: components.url!),
                  let components = URLComponents(url: url, resolvingAgainstBaseURL: true),
                  let item = components.queryItems?.first(where: { $0.name == "code" }),
                  let authCode = item.value else {
                return
            }
            
            let accessToken = await mastodonController.authorize(authorizationCode: authCode)
            
            // construct a temporary UserAccountInfo instance for the MastodonController to use to fetch its own account
            let tempAccountInfo = LocalData.UserAccountInfo(id: "temp", instanceURL: instanceURL, clientID: clientID, clientSecret: clientSecret, username: nil, accessToken: accessToken)
            mastodonController.accountInfo = tempAccountInfo
            
            let account: Account
            do {
                account = try await mastodonController.getOwnAccount()
            } catch {
                let alert = UIAlertController(title: "Unable to Verify Credentials", message: "Your account fcould not be fetcheda this time: \(error.localizedDescription)", preferredStyle: .alert)
                alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: nil))
                self.present(alert, animated: true)
                return
            }
            
            let accountInfo = LocalData.shared.addAccount(instanceURL: instanceURL, clientID: clientID, clientSecret: clientSecret, username: account.username, accessToken: accessToken)
            mastodonController.accountInfo = accountInfo
            
            self.onboardingDelegate?.didFinishOnboarding(account: accountInfo)
        }
    }
}

extension OnboardingViewController: ASWebAuthenticationPresentationContextProviding {
    func presentationAnchor(for session: ASWebAuthenticationSession) -> ASPresentationAnchor {
        return view.window!
    }
}