Tusker/Tusker/Views/Attachments/AttachmentView.swift

//
//  AttachmentView.swift
//  Tusker
//
//  Created by Shadowfacts on 8/31/18.
//  Copyright © 2018 Shadowfacts. All rights reserved.
//

import UIKit
import Pachyderm
import Gifu
import AVFoundation

protocol AttachmentViewDelegate: class {
    func showAttachmentsGallery(startingAt index: Int)
}

class AttachmentView: UIImageView, GIFAnimatable {
    
    weak var delegate: AttachmentViewDelegate?

    var playImageView: UIImageView!
    
    var attachment: Attachment!
    var index: Int!
    
    var gifData: Data?

    public lazy var animator: Animator? = Animator(withDelegate: self)

    init(attachment: Attachment, index: Int) {
        super.init(image: nil)
        commonInit()
        
        self.attachment = attachment
        self.index = index
        loadAttachment()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonInit()
    }
    
    func commonInit() {
        contentMode = .scaleAspectFill
        layer.masksToBounds = true
        isUserInteractionEnabled = true
        addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(imagePressed)))
        
        playImageView = UIImageView(image: UIImage(systemName: "play.circle.fill"))
        playImageView.translatesAutoresizingMaskIntoConstraints = false
        addSubview(playImageView)
        NSLayoutConstraint.activate([
            playImageView.widthAnchor.constraint(equalToConstant: 50),
            playImageView.heightAnchor.constraint(equalToConstant: 50),
            playImageView.centerXAnchor.constraint(equalTo: centerXAnchor),
            playImageView.centerYAnchor.constraint(equalTo: centerYAnchor)
        ])
    }
    
    func loadAttachment() {
        switch attachment.kind {
        case .image:
            loadImage()
        case .video:
            loadVideo()
        default:
            fatalError()
        }
    }
    
    func loadImage() {
        ImageCache.attachments.get(attachment.url) { [weak self] (data) in
            guard let self = self, let data = data else { return }
            DispatchQueue.main.async {
                if self.attachment.url.pathExtension == "gif" {
                    self.animate(withGIFData: data)
                    self.gifData = data
                } else {
                    self.image = UIImage(data: data)
                }
            }
        }
        
        playImageView.isHidden = true
    }
    
    func loadVideo() {
        DispatchQueue.global(qos: .userInitiated).async {
            let asset = AVURLAsset(url: self.attachment.url)
            let generator = AVAssetImageGenerator(asset: asset)
            generator.appliesPreferredTrackTransform = true
            guard let image = try? generator.copyCGImage(at: CMTime(seconds: 0, preferredTimescale: 1), actualTime: nil) else { return }
            DispatchQueue.main.async {
                self.image = UIImage(cgImage: image)
            }
        }
        
        playImageView.isHidden = false
    }
    
    override func display(_ layer: CALayer) {
        updateImageIfNeeded()
    }
    
    @objc func imagePressed() {
        delegate?.showAttachmentsGallery(startingAt: index)
    }

}