Tusker/Tusker/Views/Attachments/GifvController.swift

//
//  GifvController.swift
//  Tusker
//
//  Created by Shadowfacts on 3/18/24.
//  Copyright © 2024 Shadowfacts. All rights reserved.
//

import Foundation
import AVKit
import Combine

@MainActor
class GifvController {
    private let asset: AVAsset
    private(set) var item: AVPlayerItem
    let player: AVPlayer
    
    private var isGrayscale = false
    
    let presentationSizeSubject = PassthroughSubject<CGSize, Never>()
    private var presentationSizeObservation: NSKeyValueObservation?
    
    init(asset: AVAsset) {
        self.asset = asset
        self.item = AVPlayerItem(asset: asset)
        self.player = AVPlayer(playerItem: item)
        
        self.isGrayscale = Preferences.shared.grayscaleImages
        
        player.isMuted = true
        
        NotificationCenter.default.addObserver(self, selector: #selector(restartItem), name: .AVPlayerItemDidPlayToEndTime, object: item)
        NotificationCenter.default.addObserver(self, selector: #selector(preferencesChanged), name: .preferencesChanged, object: nil)
        
        updatePresentationSizeObservation()
    }
    
    func play() {
        if player.rate == 0 {
            player.play()
        }
    }
    
    func pause() {
        player.pause()
    }
    
    private func updatePresentationSizeObservation() {
        presentationSizeObservation = item.observe(\.presentationSize, changeHandler: { [unowned self] item, _ in
            self.presentationSizeSubject.send(item.presentationSize)
        })
    }
    
    @objc private func restartItem() {
        item.seek(to: .zero) { (success) in
            guard success else { return }
            self.player.play()
        }
    }
    
    @objc private func preferencesChanged() {
        if isGrayscale != Preferences.shared.grayscaleImages {
            isGrayscale = Preferences.shared.grayscaleImages
            item = GifvController.createItem(asset: asset)
            player.replaceCurrentItem(with: item)
            self.updatePresentationSizeObservation()
            player.play()
        }
    }
    
    private static func createItem(asset: AVAsset) -> AVPlayerItem {
        let item = AVPlayerItem(asset: asset)
        if Preferences.shared.grayscaleImages {
            #if os(visionOS)
            #warning("Use async AVVideoComposition CIFilter initializer")
            #else
            item.videoComposition = AVVideoComposition(asset: asset, applyingCIFiltersWithHandler: { (request) in
                let filter = CIFilter(name: "CIColorMonochrome")!
                
                filter.setValue(request.sourceImage, forKey: "inputImage")
                filter.setValue(CIColor(red: 0.85, green: 0.85, blue: 0.85), forKey: "inputColor")
                filter.setValue(1.0, forKey: "inputIntensity")
                
                request.finish(with: filter.outputImage!, context: nil)
            })
            #endif
        }
        return item
    }

}