//
//  PreviewView.swift
//  VisionCamera
//
//  Created by Marc Rousavy on 30.11.22.
//  Copyright © 2022 mrousavy. All rights reserved.
//

import AVFoundation
import Foundation
import UIKit

// MARK: - PreviewViewDelegate

protocol PreviewViewDelegate: AnyObject {
  func onPreviewStarted()
  func onPreviewStopped()
}

// MARK: - PreviewView

final class PreviewView: UIView {
  /**
   A delegate for listening to events of the Preview View.
   */
  weak var delegate: PreviewViewDelegate?

  /**
   Convenience wrapper to get layer as its statically known type.
   */
  var videoPreviewLayer: AVCaptureVideoPreviewLayer {
    // swiftlint:disable force_cast
    return layer as! AVCaptureVideoPreviewLayer
    // swiftlint:enable force_cast
  }

  /**
   Gets or sets the resize mode of the PreviewView.
   */
  var resizeMode: ResizeMode = .cover {
    didSet {
      switch resizeMode {
      case .cover:
        videoPreviewLayer.videoGravity = .resizeAspectFill
      case .contain:
        videoPreviewLayer.videoGravity = .resizeAspect
      }
    }
  }

  override public static var layerClass: AnyClass {
    return AVCaptureVideoPreviewLayer.self
  }

  func layerRectConverted(fromMetadataOutputRect rect: CGRect) -> CGRect {
    return videoPreviewLayer.layerRectConverted(fromMetadataOutputRect: rect)
  }

  func captureDevicePointConverted(fromLayerPoint point: CGPoint) -> CGPoint {
    return videoPreviewLayer.captureDevicePointConverted(fromLayerPoint: point)
  }

  private var isPreviewingObserver: NSKeyValueObservation?

  init(frame: CGRect, session: AVCaptureSession) {
    super.init(frame: frame)
    videoPreviewLayer.session = session
    videoPreviewLayer.videoGravity = .resizeAspectFill

    if #available(iOS 13.0, *) {
      isPreviewingObserver = videoPreviewLayer.observe(\.isPreviewing, changeHandler: { [weak self] layer, _ in
        guard let self else { return }
        if layer.isPreviewing {
          VisionLogger.log(level: .info, message: "Preview Layer started previewing.")
          self.delegate?.onPreviewStarted()
        } else {
          VisionLogger.log(level: .info, message: "Preview Layer stopped previewing.")
          self.delegate?.onPreviewStopped()
        }
      })
    }
  }

  @available(*, unavailable)
  required init?(coder _: NSCoder) {
    fatalError("init(coder:) is not implemented!")
  }
}