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

import UIKit
import Pachyderm
import AVFoundation

protocol AttachmentViewDelegate: AnyObject {
    func attachmentViewGallery(startingAt index: Int) -> GalleryViewController?
    func attachmentViewPresent(_ vc: UIViewController, animated: Bool)
}

class AttachmentView: GIFImageView {
    
    weak var delegate: AttachmentViewDelegate?

    var playImageView: UIImageView?
    var gifvView: GifvAttachmentView?
    
    var attachment: Attachment!
    var index: Int!
    var expectedSize: CGSize!
    
    private var attachmentRequest: ImageCache.Request?
    private var source: Source?
    
    var gifData: Data? {
        switch source {
        case let .gifData(_, data):
            return data
        default:
            return nil
        }
    }
    private var autoplayGifs: Bool {
        Preferences.shared.automaticallyPlayGifs && !ProcessInfo.processInfo.isLowPowerModeEnabled
    }
    
    private var isGrayscale = false

    init(attachment: Attachment, index: Int, expectedSize: CGSize) {
        super.init(image: nil)
        commonInit()
        
        self.attachment = attachment
        self.index = index
        self.expectedSize = expectedSize
        loadAttachment()
    }
    
    deinit {
        attachmentRequest?.cancel()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonInit()
    }
    
    private func commonInit() {
        contentMode = .scaleAspectFill
        layer.masksToBounds = true
        isUserInteractionEnabled = true
        addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(imagePressed)))
        
        NotificationCenter.default.addObserver(self, selector: #selector(preferencesChanged), name: .preferencesChanged, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(gifPlaybackModeChanged), name: .NSProcessInfoPowerStateDidChange, object: nil)
        
        addInteraction(UIContextMenuInteraction(delegate: self))
        
        isAccessibilityElement = true
        accessibilityTraits = [.image, .button]
    }
    
    @objc private func preferencesChanged() {
        gifPlaybackModeChanged()
        
        if isGrayscale != Preferences.shared.grayscaleImages {
            ImageGrayscalifier.queue.async {
                self.displayImage()
            }
        }
    }
    
    @objc private func gifPlaybackModeChanged() {
        // NSProcessInfoPowerStateDidChange is sometimes fired on a background thread
        DispatchQueue.main.async {
            if self.attachment.kind == .image,
               let gifData = self.gifData {
                if self.autoplayGifs && !self.isAnimatingGIF {
                    self.animate(withGIFData: gifData)
                } else if !self.autoplayGifs && self.isAnimatingGIF {
                    self.stopAnimatingGIF()
                }
            } else if self.attachment.kind == .gifv,
                      let gifvView = self.gifvView {
                if self.autoplayGifs {
                    gifvView.player.play()
                } else {
                    gifvView.player.pause()
                }
            }
        }
    }
    
    func loadAttachment() {
        guard AttachmentsContainerView.supportedAttachmentTypes.contains(attachment.kind) else {
            preconditionFailure("invalid attachment type")
        }
        
        if let hash = attachment.blurHash {
            DispatchQueue.global(qos: .default).async { [weak self] in
                guard let self = self else { return }
                let size: CGSize
                if let meta = self.attachment.meta,
                   let width = meta.width, let height = meta.height {
                    size = CGSize(width: width, height: height)
                } else if let orig = self.attachment.meta?.original,
                          let width = orig.width, let height = orig.height {
                    size = CGSize(width: width, height: height)
                } else {
                    size = self.expectedSize
                }
                
                guard var preview = UIImage(blurHash: hash, size: size) else {
                    return
                }
                
                if Preferences.shared.grayscaleImages,
                   let grayscale = ImageGrayscalifier.convert(url: nil, cgImage: preview.cgImage!) {
                    preview = grayscale
                }
                
                DispatchQueue.main.async { [weak self] in
                    guard let self = self, self.image == nil else { return }
                    self.image = preview
                }
            }
        }
        
        switch attachment.kind {
        case .image:
            loadImage()
        case .video:
            loadVideo()
        case .audio:
            loadAudio()
        case .gifv:
            loadGifv()
        default:
            preconditionFailure("invalid attachment type")
        }
    }
    
    func loadImage() {
        let attachmentURL = attachment.url
        attachmentRequest = ImageCache.attachments.get(attachmentURL) { [weak self] (data, _) in
            guard let self = self, let data = data else { return }
            DispatchQueue.main.async {
                self.attachmentRequest = nil
            }
            if self.attachment.url.pathExtension == "gif" {
                self.source = .gifData(attachmentURL, data)
                if self.autoplayGifs {
                    DispatchQueue.main.async {
                        self.animate(withGIFData: data)
                    }
                } else {
                    self.displayImage()
                }
            } else {
                self.source = .imageData(attachmentURL, data)
                self.displayImage()
            }
        }
    }
    
    func loadVideo() {
        if let previewURL = self.attachment.previewURL {
            attachmentRequest = ImageCache.attachments.get(previewURL, completion: { [weak self] (data, _ )in
                guard let self = self, let data = data else { return }
                DispatchQueue.main.async {
                    self.attachmentRequest = nil
                    self.source = .imageData(previewURL, data)
                    self.displayImage()
                }
            })
        } else {
            let attachmentURL = self.attachment.url
            // todo: use a single dispatch queue
            DispatchQueue.global(qos: .userInitiated).async {
                let asset = AVURLAsset(url: attachmentURL)
                let generator = AVAssetImageGenerator(asset: asset)
                generator.appliesPreferredTrackTransform = true
                guard let image = try? generator.copyCGImage(at: .zero, actualTime: nil) else { return }
                self.source = .cgImage(attachmentURL, image)
                self.displayImage()
            }
        }
        
        let 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 loadAudio() {
        let label = UILabel()
        label.text = "Audio Only"
        let playImageView = UIImageView(image: UIImage(systemName: "play.circle.fill"))
        let stack = UIStackView(arrangedSubviews: [
            label,
            playImageView
        ])
        stack.translatesAutoresizingMaskIntoConstraints = false
        stack.axis = .vertical
        stack.spacing = 8
        stack.alignment = .center
        addSubview(stack)
        NSLayoutConstraint.activate([
            stack.centerXAnchor.constraint(equalTo: centerXAnchor),
            stack.centerYAnchor.constraint(equalTo: centerYAnchor),
            playImageView.widthAnchor.constraint(equalToConstant: 50),
            playImageView.heightAnchor.constraint(equalToConstant: 50),
        ])
    }
    
    func loadGifv() {
        let attachmentURL = self.attachment.url
        let asset = AVURLAsset(url: attachmentURL)
        DispatchQueue.global(qos: .userInitiated).async {
            let generator = AVAssetImageGenerator(asset: asset)
            generator.appliesPreferredTrackTransform = true
            guard let image = try? generator.copyCGImage(at: .zero, actualTime: nil) else { return }
            self.source = .cgImage(attachmentURL, image)
            self.displayImage()
        }
        
        let gifvView = GifvAttachmentView(asset: asset, gravity: .resizeAspectFill)
        self.gifvView = gifvView
        gifvView.translatesAutoresizingMaskIntoConstraints = false
        if autoplayGifs {
            gifvView.player.play()
        }
        addSubview(gifvView)
        NSLayoutConstraint.activate([
            gifvView.leadingAnchor.constraint(equalTo: leadingAnchor),
            gifvView.trailingAnchor.constraint(equalTo: trailingAnchor),
            gifvView.topAnchor.constraint(equalTo: topAnchor),
            gifvView.bottomAnchor.constraint(equalTo: bottomAnchor),
        ])
    }
    
    private func displayImage() {
        isGrayscale = Preferences.shared.grayscaleImages
        
        let image: UIImage?
        
        switch source {
        case nil:
            image = nil
            
        case let .imageData(url, data), let .gifData(url, data):
            if isGrayscale {
                image = ImageGrayscalifier.convert(url: url, data: data)
            } else {
                image = UIImage(data: data)
            }
            
        case let .cgImage(url, cgImage):
            if isGrayscale {
                image = ImageGrayscalifier.convert(url: url, cgImage: cgImage)
            } else {
                image = UIImage(cgImage: cgImage)
            }
        }
        
        DispatchQueue.main.async {
            self.image = image
        }
    }
    
    func showGallery() {
        if let delegate = delegate,
           let gallery = delegate.attachmentViewGallery(startingAt: index) {
            delegate.attachmentViewPresent(gallery, animated: true)
        }
    }
    
    @objc func imagePressed() {
        showGallery()
    }
    
    // MARK: - Accessibility
    
    override func accessibilityActivate() -> Bool {
        showGallery()
        return true
    }

}

fileprivate extension AttachmentView {
    enum Source {
        case imageData(URL, Data)
        case gifData(URL, Data)
        case cgImage(URL, CGImage)
    }
}

extension AttachmentView: UIContextMenuInteractionDelegate {
    func contextMenuInteraction(_ interaction: UIContextMenuInteraction, configurationForMenuAtLocation location: CGPoint) -> UIContextMenuConfiguration? {
        return UIContextMenuConfiguration(identifier: nil, previewProvider: { () -> UIViewController? in
            if self.attachment.kind == .image {
                return AttachmentPreviewViewController(attachment: self.attachment)
            } else if self.attachment.kind == .gifv {
                let vc = GifvAttachmentViewController(attachment: self.attachment)
                vc.preferredContentSize = self.image?.size ?? .zero
                return vc
            } else {
                return self.delegate?.attachmentViewGallery(startingAt: self.index)
            }
        }, actionProvider: nil)
    }
    func contextMenuInteraction(_ interaction: UIContextMenuInteraction, willPerformPreviewActionForMenuWith configuration: UIContextMenuConfiguration, animator: UIContextMenuInteractionCommitAnimating) {
        animator.addCompletion {
            animator.preferredCommitStyle = .pop
            if let gallery = animator.previewViewController as? GalleryViewController {
                self.delegate?.attachmentViewPresent(gallery, animated: true)
            } else {
                self.showGallery()
            }
        }
    }
}