Tusker/Tusker/Screens/Explore/TrendingLinkTableViewCell.swift

//
//  TrendingLinkTableViewCell.swift
//  Tusker
//
//  Created by Shadowfacts on 4/2/22.
//  Copyright © 2022 Shadowfacts. All rights reserved.
//

import UIKit
import Pachyderm
import WebURLFoundationExtras

class TrendingLinkTableViewCell: UITableViewCell {
    
    private var card: Card?
    private var isGrayscale = false
    private var thumbnailRequest: ImageCache.Request?
    
    private let thumbnailView = UIImageView()
    private let titleLabel = UILabel()
    private let providerLabel = UILabel()
    private let activityLabel = UILabel()
    private let historyView = TrendHistoryView()
    
    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        
        thumbnailView.contentMode = .scaleAspectFill
        thumbnailView.clipsToBounds = true
        
        titleLabel.font = UIFont(descriptor: .preferredFontDescriptor(withTextStyle: .headline).withSymbolicTraits(.traitBold)!, size: 0)
        titleLabel.numberOfLines = 2
        
        providerLabel.font = .preferredFont(forTextStyle: .subheadline)
        
        activityLabel.font = .preferredFont(forTextStyle: .caption1)
        
        let vStack = UIStackView(arrangedSubviews: [
            titleLabel,
            providerLabel,
            activityLabel,
        ])
        vStack.axis = .vertical
        vStack.spacing = 4
        
        let hStack = UIStackView(arrangedSubviews: [
            thumbnailView,
            vStack,
            historyView,
        ])
        hStack.axis = .horizontal
        hStack.spacing = 4
        hStack.alignment = .center
        hStack.translatesAutoresizingMaskIntoConstraints = false
        addSubview(hStack)
        
        NSLayoutConstraint.activate([
            thumbnailView.heightAnchor.constraint(equalToConstant: 75),
            thumbnailView.widthAnchor.constraint(equalTo: thumbnailView.heightAnchor),
            
            historyView.widthAnchor.constraint(equalToConstant: 75),
            historyView.heightAnchor.constraint(equalToConstant: 44),
            
            hStack.leadingAnchor.constraint(equalToSystemSpacingAfter: safeAreaLayoutGuide.leadingAnchor, multiplier: 1),
            safeAreaLayoutGuide.trailingAnchor.constraint(equalToSystemSpacingAfter: hStack.trailingAnchor, multiplier: 1),
            hStack.topAnchor.constraint(equalToSystemSpacingBelow: topAnchor, multiplier: 1),
            bottomAnchor.constraint(equalToSystemSpacingBelow: hStack.bottomAnchor, multiplier: 1),
        ])
        
        NotificationCenter.default.addObserver(self, selector: #selector(updateUIForPreferences), name: .preferencesChanged, object: nil)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        
        thumbnailView.layer.cornerRadius = 0.05 * thumbnailView.bounds.width
    }
    
    override func updateConfiguration(using state: UICellConfigurationState) {
        var config = UIBackgroundConfiguration.listGroupedCell().updated(for: state)
        if state.isHighlighted || state.isSelected {
            config.backgroundColor = .appSelectedCellBackground
        } else {
            config.backgroundColor = .appGroupedCellBackground
        }
        backgroundConfiguration = config
    }

    func updateUI(card: Card) {
        self.card = card
        self.thumbnailView.image = nil
        
        updateGrayscaleableUI(card: card)
        updateUIForPreferences()
        
        let title = card.title.trimmingCharacters(in: .whitespacesAndNewlines)
        titleLabel.text = title
        titleLabel.isHidden = title.isEmpty
        
        let provider = card.providerName?.trimmingCharacters(in: .whitespacesAndNewlines)
        providerLabel.text = provider
        providerLabel.isHidden = provider?.isEmpty ?? true
        
        if let history = card.history {
            let sorted = history.sorted(by: { $0.day < $1.day })
            let lastTwo = sorted[(sorted.count - 2)...]
            let accounts = lastTwo.map(\.accounts).reduce(0, +)
            let uses = lastTwo.map(\.uses).reduce(0, +)
            
            let format = NSLocalizedString("trending hashtag info", comment: "trending hashtag posts and people")
            activityLabel.text = String.localizedStringWithFormat(format, accounts, uses)
            activityLabel.isHidden = false
        } else {
            activityLabel.isHidden = true
        }
        
        historyView.setHistory(card.history)
        historyView.isHidden = card.history == nil || card.history!.count < 2
    }
    
    @objc private func updateUIForPreferences() {
        if isGrayscale != Preferences.shared.grayscaleImages,
           let card {
            updateGrayscaleableUI(card: card)
        }
    }
    
    private func updateGrayscaleableUI(card: Card) {
        isGrayscale = Preferences.shared.grayscaleImages
        
        if let imageURL = card.image,
           let url = URL(imageURL) {
            thumbnailRequest = ImageCache.attachments.get(url, completion: { _, image in
                guard let image = image,
                      let transformedImage = ImageGrayscalifier.convertIfNecessary(url: url, image: image) else {
                    return
                }
                DispatchQueue.main.async {
                    self.thumbnailView.image = transformedImage
                }
            })
            if thumbnailRequest != nil {
                loadBlurHash(card: card)
            }
        }
    }
    
    private func loadBlurHash(card: Card) {
        guard let hash = card.blurhash else {
            return
        }
        AttachmentView.queue.async { [weak self] in
            let size: CGSize
            if let width = card.width, let height = card.height {
                let aspectRatio = CGFloat(width) / CGFloat(height)
                if aspectRatio > 1 {
                    size = CGSize(width: 32, height: 32 / aspectRatio)
                } else {
                    size = CGSize(width: 32 * aspectRatio, height: 32)
                }
            } else {
                size = CGSize(width: 32, height: 32)
            }
            
            guard let preview = UIImage(blurHash: hash, size: size) else {
                return
            }
            DispatchQueue.main.async { [weak self] in
                guard let self = self,
                      self.card?.url == card.url,
                      self.thumbnailView.image == nil else {
                    return
                }
                self.thumbnailView.image = preview
            }
        }
    }

}