Tusker/Tusker/Screens/Notifications/NotificationLoadingViewController.swift

//
//  NotificationLoadingViewController.swift
//  Tusker
//
//  Created by Shadowfacts on 4/12/24.
//  Copyright © 2024 Shadowfacts. All rights reserved.
//

import UIKit
import Pachyderm

class NotificationLoadingViewController: UIViewController {
    
    private let notificationID: String
    private let mastodonController: MastodonController
    
    init(notificationID: String, mastodonController: MastodonController) {
        self.notificationID = notificationID
        self.mastodonController = mastodonController
        
        super.init(nibName: nil, bundle: nil)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .secondarySystemBackground
        
        let indicator = UIActivityIndicatorView(style: .medium)
        indicator.startAnimating()
        indicator.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(indicator)
        NSLayoutConstraint.activate([
            indicator.centerXAnchor.constraint(equalTo: view.safeAreaLayoutGuide.centerXAnchor),
            indicator.centerYAnchor.constraint(equalTo: view.safeAreaLayoutGuide.centerYAnchor),
        ])
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        Task {
            let request = Client.getNotification(id: notificationID)
            do {
                let (notification, _) = try await mastodonController.run(request)
                await withCheckedContinuation { continuation in
                    let container = mastodonController.persistentContainer
                    let context = container.viewContext
                    container.addAll(notifications: [notification], in: context) {
                        continuation.resume()
                    }
                }
                showNotification(notification)
            } catch {
                showLoadingError(error)
            }
        }
    }
    
    private func showNotification(_ notification: Pachyderm.Notification) {
        let vc: UIViewController
        switch notification.kind {
        case .mention, .status, .poll, .update:
            guard let statusID = notification.status?.id else {
                showLoadingError(Error.missingStatus)
                return
            }
            vc = ConversationViewController(for: statusID, state: .unknown, mastodonController: mastodonController)
        case .reblog, .favourite:
            guard let statusID = notification.status?.id else {
                showLoadingError(Error.missingStatus)
                return
            }
            let actionType = notification.kind == .reblog ? StatusActionAccountListViewController.ActionType.reblog : .favorite
            vc = StatusActionAccountListViewController(actionType: actionType, statusID: statusID, statusState: .unknown, accountIDs: [notification.account.id], mastodonController: mastodonController)
        case .emojiReaction:
            guard let statusID = notification.status?.id else {
                showLoadingError(Error.missingStatus)
                return
            }
            guard let emoji = notification.emoji else {
                showLoadingError(Error.unknownType)
                return
            }
            let actionType = StatusActionAccountListViewController.ActionType.emojiReaction(emoji, notification.emojiURL)
            vc = StatusActionAccountListViewController(actionType: actionType, statusID: statusID, statusState: .unknown, accountIDs: [notification.account.id], mastodonController: mastodonController)
        case .follow:
            vc = ProfileViewController(accountID: notification.account.id, mastodonController: mastodonController)
        case .followRequest:
            vc = FollowRequestNotificationViewController(notification: notification, mastodonController: mastodonController)
        case .unknown:
            showLoadingError(Error.unknownType)
            return
        }
        guard let navigationController else {
            fatalError("Don't know how to show notification VC outside of navigation controller: parent is \(parent?.description ?? "<nil>")")
        }
        navigationController.viewControllers[navigationController.viewControllers.count - 1] = vc
    }
    
    private func showLoadingError(_ error: any Swift.Error) {
        let image = UIImageView(image: UIImage(systemName: "exclamationmark.triangle.fill")!)
        image.tintColor = .secondaryLabel
        image.contentMode = .scaleAspectFit
        
        let title = UILabel()
        title.textColor = .secondaryLabel
        title.font = .preferredFont(forTextStyle: .title1).withTraits(.traitBold)!
        title.adjustsFontForContentSizeCategory = true
        title.text = "Couldn't Load Notification"
        
        let subtitle = UILabel()
        subtitle.textColor = .secondaryLabel
        subtitle.font = .preferredFont(forTextStyle: .body)
        subtitle.adjustsFontForContentSizeCategory = true
        subtitle.numberOfLines = 0
        subtitle.textAlignment = .center
        if let error = error as? Error {
            subtitle.text = error.localizedDescription
        } else if let error = error as? Client.Error {
            subtitle.text = error.localizedDescription
        } else {
            subtitle.text = error.localizedDescription
        }
        
        let stack = UIStackView(arrangedSubviews: [
            image,
            title,
            subtitle,
        ])
        stack.axis = .vertical
        stack.alignment = .center
        stack.spacing = 8
        stack.isAccessibilityElement = true
        stack.accessibilityLabel = "\(title.text!). \(subtitle.text!)"
        
        stack.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(stack)
        NSLayoutConstraint.activate([
            image.widthAnchor.constraint(equalToConstant: 64),
            image.heightAnchor.constraint(equalToConstant: 64),
            
            stack.leadingAnchor.constraint(equalToSystemSpacingAfter: view.safeAreaLayoutGuide.leadingAnchor, multiplier: 1),
            view.safeAreaLayoutGuide.trailingAnchor.constraint(equalToSystemSpacingAfter: stack.trailingAnchor, multiplier: 1),
            stack.centerYAnchor.constraint(equalTo: view.safeAreaLayoutGuide.centerYAnchor),
        ])
    }

}

private enum Error: LocalizedError {
    case missingStatus
    case unknownType
    
    var errorDescription: String? {
        switch self {
        case .missingStatus:
            "Missing status for mention/status notification"
        case .unknownType:
            "Unknown notification type"
        }
    }
}