//
//  ActionNotificationGroupTableViewCell.swift
//  Tusker
//
//  Created by Shadowfacts on 9/5/19.
//  Copyright © 2019 Shadowfacts. All rights reserved.
//

import UIKit
import Pachyderm
import SwiftSoup

class ActionNotificationGroupTableViewCell: UITableViewCell {

    weak var delegate: TuskerNavigationDelegate?
    var mastodonController: MastodonController! { delegate?.apiController }
    
    @IBOutlet weak var actionImageView: UIImageView!
    @IBOutlet weak var verticalStackView: UIStackView!
    @IBOutlet weak var actionAvatarStackView: UIStackView!
    @IBOutlet weak var timestampLabel: UILabel!
    @IBOutlet weak var actionLabel: MultiSourceEmojiLabel!
    @IBOutlet weak var statusContentLabel: UILabel!

    var group: NotificationGroup!
    var statusID: String!
    
    private var avatarRequests = [String: ImageCache.Request]()
    private var updateTimestampWorkItem: DispatchWorkItem?
    private var isGrayscale = false
    
    deinit {
        updateTimestampWorkItem?.cancel()
    }
    
    override func awakeFromNib() {
        super.awakeFromNib()
        
        actionLabel.combiner = self.updateActionLabel
        
        NotificationCenter.default.addObserver(self, selector: #selector(updateUIForPreferences), name: .preferencesChanged, object: nil)
    }

    @objc func updateUIForPreferences() {
        for case let imageView as UIImageView in actionAvatarStackView.arrangedSubviews {
            imageView.layer.cornerRadius = Preferences.shared.avatarStyle.cornerRadius(for: imageView)
        }
        
        if isGrayscale != Preferences.shared.grayscaleImages {
            updateGrayscaleableUI()
        }
    }
    
    func updateUI(group: NotificationGroup) {
        guard group.kind == .favourite || group.kind == .reblog else {
            fatalError("Invalid notification type \(group.kind) for ActionNotificationGroupTableViewCell")
        }
        self.group = group
        
        guard let firstNotification = group.notifications.first else { fatalError() }
        let status = firstNotification.status!
        self.statusID = status.id
        
        updateUIForPreferences()
        
        switch group.kind {
        case .favourite:
            actionImageView.image = UIImage(systemName: "star.fill")
        case .reblog:
            actionImageView.image = UIImage(systemName: "repeat")
        default:
            fatalError()
        }
        
        isGrayscale = Preferences.shared.grayscaleImages
        
        let people = group.notifications.compactMap { mastodonController.persistentContainer.account(for: $0.account.id) }
        
        actionAvatarStackView.arrangedSubviews.forEach { $0.removeFromSuperview() }
        var imageViews = [UIImageView]()
        for account in people {
            let imageView = UIImageView()
            imageView.translatesAutoresizingMaskIntoConstraints = false
            imageView.layer.masksToBounds = true
            imageView.layer.cornerRadius = Preferences.shared.avatarStyle.cornerRadiusFraction * 30
            let avatarURL = account.avatar
            avatarRequests[account.id] = ImageCache.avatars.get(avatarURL) { [weak self] (_, image) in
                guard let self = self else { return }
                guard let image = image,
                      self.group.id == group.id,
                      let transformedImage = ImageGrayscalifier.convertIfNecessary(url: avatarURL, image: image) else {
                    DispatchQueue.main.async {
                        self.avatarRequests.removeValue(forKey: account.id)
                    }
                    return
                }
                
                DispatchQueue.main.async {
                    self.avatarRequests.removeValue(forKey: account.id)
                    imageView.image = transformedImage
                }
            }
            actionAvatarStackView.addArrangedSubview(imageView)
            imageViews.append(imageView)
            
            // don't add more avatars if they would overflow or squeeze the timestamp label
            let avatarViewsWidth = 30 * CGFloat(imageViews.count)
            let avatarMarginsWidth = 4 * CGFloat(max(0, imageViews.count - 1))
            let maxAvatarStackWidth = verticalStackView.bounds.width - timestampLabel.bounds.width - 8
            let remainingWidth = maxAvatarStackWidth - avatarViewsWidth - avatarMarginsWidth
            if remainingWidth < 34 {
                break
            }
        }
        NSLayoutConstraint.activate(imageViews.map { $0.widthAnchor.constraint(equalTo: $0.heightAnchor) })

        updateTimestamp()
        actionLabel.setEmojis(pairs: people.map { ($0.displayOrUserName, $0.emojis) }, identifier: group.id)
        
        let doc = try! SwiftSoup.parse(status.content)
        statusContentLabel.text = try! doc.text()
    }
    
    private func updateGrayscaleableUI() {
        let people = group.notifications.compactMap { mastodonController.persistentContainer.account(for: $0.account.id) }
        let groupID = group.id
        
        for (index, account) in people.enumerated() {
            guard actionAvatarStackView.arrangedSubviews.count > index,
                  let imageView = actionAvatarStackView.arrangedSubviews[index] as? UIImageView else {
                continue
            }
            
            let avatarURL = account.avatar
            avatarRequests[account.id] = ImageCache.avatars.get(avatarURL) { [weak self] (_, image) in
                guard let self = self else { return }
                guard let image = image,
                      self.group.id == groupID,
                      let transformedImage = ImageGrayscalifier.convertIfNecessary(url: avatarURL, image: image) else {
                    DispatchQueue.main.async {
                        self.avatarRequests.removeValue(forKey: account.id)
                    }
                    return
                }
                
                DispatchQueue.main.async {
                    self.avatarRequests.removeValue(forKey: account.id)
                    imageView.image = transformedImage
                }
            }
        }
    }
    
    private func updateTimestamp() {
        guard let notification = group.notifications.first else {
            fatalError("Missing cached notification")
        }
        
        timestampLabel.text = notification.createdAt.timeAgoString()

        let delay: DispatchTimeInterval?
        switch notification.createdAt.timeAgo().1 {
        case .second:
            delay = .seconds(10)
        case .minute:
            delay = .seconds(60)
        default:
            delay = nil
        }
        if let delay = delay {
            if updateTimestampWorkItem == nil {
                updateTimestampWorkItem = DispatchWorkItem { [weak self] in
                    self?.updateTimestamp()
                }
            }
            DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: updateTimestampWorkItem!)
        } else {
            updateTimestampWorkItem = nil
        }
    }
    
    func updateActionLabel(names: [NSAttributedString]) -> NSAttributedString {
        let verb: String
        switch group.kind {
        case .favourite:
            verb = "Favorited"
        case .reblog:
            verb = "Reblogged"
        default:
            fatalError()
        }
        
        // todo: figure out how to localize this
        let str = NSMutableAttributedString(string: "\(verb) by ")
        switch names.count {
        case 1:
            str.append(names.first!)
        case 2:
            str.append(names.first!)
            str.append(NSAttributedString(string: " and "))
            str.append(names.last!)
        default:
            for (index, name) in names.enumerated() {
                str.append(name)
                if index < names.count - 2 {
                    str.append(NSAttributedString(string: ", "))
                } else if index == names.count - 2 {
                    str.append(NSAttributedString(string: ", and "))
                }
            }
        }
        return str
    }
    
    override func prepareForReuse() {
        super.prepareForReuse()
        
        avatarRequests.values.forEach { $0.cancel() }
        updateTimestampWorkItem?.cancel()
        updateTimestampWorkItem = nil
    }

}

extension ActionNotificationGroupTableViewCell: SelectableTableViewCell {
    func didSelectCell() {
        guard let delegate = delegate else { return }
        let notifications = group.notifications
        let accountIDs = notifications.map { $0.account.id }
        let action: StatusActionAccountListTableViewController.ActionType
        switch notifications.first!.kind {
        case .favourite:
            action = .favorite
        case .reblog:
            action = .reblog
        default:
            fatalError()
        }
        let vc = delegate.statusActionAccountList(action: action, statusID: statusID, statusState: .unknown, accountIDs: accountIDs)
        delegate.show(vc)
    }
}

extension ActionNotificationGroupTableViewCell: MenuPreviewProvider {
    var navigationDelegate: TuskerNavigationDelegate? { return delegate }
    
    func getPreviewProviders(for location: CGPoint, sourceViewController: UIViewController) -> PreviewProviders? {
        return (content: {
            let notifications = self.group.notifications
            let accountIDs = notifications.map { $0.account.id }
            let action: StatusActionAccountListTableViewController.ActionType
            switch notifications.first!.kind {
            case .favourite:
                action = .favorite
            case .reblog:
                action = .reblog
            default:
                fatalError()
            }
            return self.delegate?.statusActionAccountList(action: action, statusID: self.statusID, statusState: .unknown, accountIDs: accountIDs)
        }, actions: {
            return []
        })
    }
}