Tusker/Tusker/Screens/Gallery/VideoGalleryContentViewController.swift

//
//  VideoGalleryContentViewController.swift
//  Tusker
//
//  Created by Shadowfacts on 3/19/24.
//  Copyright © 2024 Shadowfacts. All rights reserved.
//

import UIKit
import GalleryVC
import AVFoundation

class VideoGalleryContentViewController: UIViewController, GalleryContentViewController {
    private let url: URL
    let caption: String?
    private let item: AVPlayerItem
    let player: AVPlayer
    
    private var presentationSizeObservation: NSKeyValueObservation?
    private var statusObservation: NSKeyValueObservation?
    private var isFirstAppearance = true
    
    init(url: URL, caption: String?) {
        self.url = url
        self.caption = caption
        
        let asset = AVAsset(url: url)
        self.item = AVPlayerItem(asset: asset)
        self.player = AVPlayer(playerItem: item)
        
        super.init(nibName: nil, bundle: nil)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        container?.setGalleryContentLoading(true)
        
        let playerView = PlayerView(item: item, player: player)
        playerView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(playerView)
        NSLayoutConstraint.activate([
            playerView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            playerView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            playerView.topAnchor.constraint(equalTo: view.topAnchor),
            playerView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
        ])
        
        presentationSizeObservation = item.observe(\.presentationSize, changeHandler: { [unowned self] item, _ in
            MainActor.runUnsafely {
                self.preferredContentSize = item.presentationSize
                self.container?.galleryContentChanged()
            }
        })
        statusObservation = item.observe(\.status, changeHandler: { [unowned self] item, _ in
            MainActor.runUnsafely {
                if item.status == .readyToPlay {
                    self.container?.setGalleryContentLoading(false)
                    statusObservation = nil
                }
            }
        })
        
        preferredContentSize = item.presentationSize
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        if isFirstAppearance {
            isFirstAppearance = false
            player.play()
        }
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        
        player.pause()
    }
    
    // MARK: GalleryContentViewController
    
    var container: (any GalleryVC.GalleryContentViewControllerContainer)?
    
    var contentSize: CGSize {
        item.presentationSize
    }
    
    var activityItemsForSharing: [Any] {
        [VideoActivityItemSource(asset: item.asset, url: url)]
    }
    
}

private class PlayerView: UIView {
    override class var layerClass: AnyClass {
        AVPlayerLayer.self
    }
    
    private var playerLayer: AVPlayerLayer {
        layer as! AVPlayerLayer
    }
    
    private let player: AVPlayer
    private var presentationSizeObservation: NSKeyValueObservation?
    
    override var intrinsicContentSize: CGSize {
        player.currentItem?.presentationSize ?? CGSize(width: UIView.noIntrinsicMetric, height: UIView.noIntrinsicMetric)
    }
    
    init(item: AVPlayerItem, player: AVPlayer) {
        self.player = player
        
        super.init(frame: .zero)
        
        playerLayer.player = player
        playerLayer.videoGravity = .resizeAspect
        
        presentationSizeObservation = item.observe(\.presentationSize, changeHandler: { [unowned self] _, _ in
            MainActor.runUnsafely {
                self.invalidateIntrinsicContentSize()
            }
        })
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}