Tusker/Tusker/Screens/Notifications/NotificationsTableViewController.swift

//
//  NotificationsTableViewController.swift
//  Tusker
//
//  Created by Shadowfacts on 9/2/18.
//  Copyright © 2018 Shadowfacts. All rights reserved.
//

import UIKit
import Pachyderm

class NotificationsTableViewController: EnhancedTableViewController {
    
    var timelineSegments: [TimelineSegment<Pachyderm.Notification>] = [] {
        didSet {
            DispatchQueue.main.async {
                self.tableView.reloadData()
            }
        }
    }
    
    var newer: RequestRange?
    var older: RequestRange?
    
    init() {
        super.init(style: .plain)
        
        title = "Notifications"
        tabBarItem.image = UIImage(systemName: "bell.fill")
        
        self.refreshControl = UIRefreshControl()
        refreshControl!.addTarget(self, action: #selector(refreshNotifications(_:)), for: .valueChanged)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        tableView.rowHeight = UITableView.automaticDimension
        tableView.estimatedRowHeight = 140
        
        tableView.register(UINib(nibName: "StatusTableViewCell", bundle: nil), forCellReuseIdentifier: "statusCell")
        tableView.register(UINib(nibName: "ActionNotificationTableViewCell", bundle: nil), forCellReuseIdentifier: "actionCell")
        tableView.register(UINib(nibName: "FollowNotificationTableViewCell", bundle: nil), forCellReuseIdentifier: "followCell")
        
        tableView.prefetchDataSource = self
        
        let request = MastodonController.client.getNotifications()
        MastodonController.client.run(request) { result in
            guard case let .success(notifications, pagination) = result else { fatalError() }
            
            self.timelineSegments.append(TimelineSegment(objects: notifications))
            MastodonCache.addAll(notifications: notifications)
            MastodonCache.addAll(statuses: notifications.compactMap { $0.status })
            MastodonCache.addAll(accounts: notifications.map { $0.account })
            
            self.newer = pagination?.newer
            self.older = pagination?.older
        }
        
        userActivity = UserActivityManager.checkNotificationsActivity()
    }
    
    // MARK: - Table view data source

    override func numberOfSections(in tableView: UITableView) -> Int {
        return timelineSegments.count
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return timelineSegments[section].count
    }

    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let notificationID = timelineSegments[indexPath.section][indexPath.row]
        guard let notification = MastodonCache.notification(for: notificationID) else { fatalError() }
        
        switch notification.kind {
        case .mention:
            guard let cell = tableView.dequeueReusableCell(withIdentifier: "statusCell", for: indexPath) as? StatusTableViewCell else { fatalError() }
            cell.updateUI(statusID: notification.status!.id)
            cell.delegate = self
            return cell
        case .favourite, .reblog:
            guard let cell = tableView.dequeueReusableCell(withIdentifier: "actionCell", for: indexPath) as? ActionNotificationTableViewCell else { fatalError() }
            cell.updateUI(for: notification)
            cell.delegate = self
            return cell
        case .follow:
            guard let cell = tableView.dequeueReusableCell(withIdentifier: "followCell", for: indexPath) as? FollowNotificationTableViewCell else { fatalError() }
            cell.updateUI(for: notification)
            cell.delegate = self
            return cell
        }
    }
 

    override func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
        if indexPath.section == timelineSegments.count - 1,
            indexPath.row == timelineSegments[indexPath.section].count - 1 {
            guard let older = older else { return }
            
            let request = MastodonController.client.getNotifications(range: older)
            MastodonController.client.run(request) { result in
                guard case let .success(newNotifications, pagination) = result else { fatalError() }
                
                self.timelineSegments[self.timelineSegments.count - 1].append(objects: newNotifications)
                MastodonCache.addAll(notifications: newNotifications)
                MastodonCache.addAll(statuses: newNotifications.compactMap { $0.status })
                MastodonCache.addAll(accounts: newNotifications.map { $0.account })

                self.older = pagination?.older
            }
        }
    }
    
    override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
        return true
    }
    
    override func tableView(_ tableView: UITableView, leadingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration? {
        return (tableView.cellForRow(at: indexPath) as? TableViewSwipeActionProvider)?.leadingSwipeActionsConfiguration()
    }
    
    override func tableView(_ tableView: UITableView, trailingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration? {
        return (tableView.cellForRow(at: indexPath) as? TableViewSwipeActionProvider)?.trailingSwipeActionsConfiguration()
    }
    
    @objc func refreshNotifications(_ sender: Any) {
        guard let newer = newer else { return }
        
        let request = MastodonController.client.getNotifications(range: newer)
        MastodonController.client.run(request) { result in
            guard case let .success(newNotifications, pagination) = result else { fatalError() }
            
            self.timelineSegments[0].insertAtBeginning(objects: newNotifications)
            MastodonCache.addAll(notifications: newNotifications)
            MastodonCache.addAll(statuses: newNotifications.compactMap { $0.status })
            MastodonCache.addAll(accounts: newNotifications.map { $0.account })

            self.newer = pagination?.newer
            
            DispatchQueue.main.async {
                self.refreshControl?.endRefreshing()
                
                // maintain the current position in the list (don't scroll to top)
                self.tableView.scrollToRow(at: IndexPath(row: newNotifications.count, section: 0), at: .top, animated: false)
            }
        }
    }

}

extension NotificationsTableViewController: StatusTableViewCellDelegate {}

extension NotificationsTableViewController: UITableViewDataSourcePrefetching {
    func tableView(_ tableView: UITableView, prefetchRowsAt indexPaths: [IndexPath]) {
        for indexPath in indexPaths {
            let notificationID = timelineSegments[indexPath.section][indexPath.row]
            guard let notification = MastodonCache.notification(for: notificationID) else { continue }
            ImageCache.avatars.get(notification.account.avatar, completion: nil)
        }
    }
    
    func tableView(_ tableView: UITableView, cancelPrefetchingForRowsAt indexPaths: [IndexPath]) {
        for indexPath in indexPaths {
            let notificationID = timelineSegments[indexPath.section][indexPath.row]
            guard let notification = MastodonCache.notification(for: notificationID) else { continue }
            ImageCache.avatars.cancel(notification.account.url)
        }
    }
}