// Copyright 2024-present 650 Industries. All rights reserved.

/**
 Transformer that makes sure the image is oriented up and not mirrored.
 Guarantees that the original pixel data matches the displayed orientation.
 */
internal struct ImageFixOrientationTransformer: ImageTransformer {
  func transform(image: UIImage) async throws -> UIImage {
    guard let cgImage = image.cgImage else {
      throw ImageNotFoundException()
    }
    guard var colorSpace = cgImage.colorSpace else {
      // That should never happen as `colorSpace` is empty only when the image is a mask.
      throw ImageColorSpaceNotFoundException()
    }
    if !colorSpace.supportsOutput {
      colorSpace = CGColorSpaceCreateDeviceRGB()
    }

    var transform = CGAffineTransform.identity

    switch image.imageOrientation {
    case .down, .downMirrored:
      transform = transform.translatedBy(x: image.size.width, y: image.size.height)
      transform = transform.rotated(by: Double.pi)
    case .left, .leftMirrored:
      transform = transform.translatedBy(x: image.size.width, y: 0)
      transform = transform.rotated(by: Double.pi / 2)
    case .right, .rightMirrored:
      transform = transform.translatedBy(x: 0, y: image.size.height)
      transform = transform.rotated(by: -Double.pi / 2)
    default:
      break
    }

    switch image.imageOrientation {
    case .upMirrored, .downMirrored:
      transform = transform.translatedBy(x: image.size.width, y: 0)
      transform = transform.scaledBy(x: -1, y: 1)
    case .leftMirrored, .rightMirrored:
      transform = transform.translatedBy(x: image.size.height, y: 0)
      transform = transform.scaledBy(x: -1, y: 1)
    default:
      break
    }

    let context = CGContext(
      data: nil,
      width: Int(image.size.width),
      height: Int(image.size.height),
      bitsPerComponent: cgImage.bitsPerComponent,
      bytesPerRow: 0,
      space: colorSpace,
      bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue
    )

    guard let context = context else {
      throw ImageContextLostException()
    }

    context.concatenate(transform)

    switch image.imageOrientation {
    case .left, .leftMirrored, .right, .rightMirrored:
      context.draw(cgImage, in: CGRect(x: 0, y: 0, width: image.size.height, height: image.size.width))
    default:
      context.draw(cgImage, in: CGRect(x: 0, y: 0, width: image.size.width, height: image.size.height))
    }

    guard let newCGImage = context.makeImage() else {
      throw ImageDrawingFailedException()
    }
    return UIImage(cgImage: newCGImage)
  }
}