# A MediaFile for a JPEG, PNG, or GIF file. Uses libvips for resizing images.
#
# @see https://github.com/libvips/ruby-vips
# @see https://libvips.github.io/libvips/API/current
class MediaFile::Image < MediaFile
  # http://jcupitt.github.io/libvips/API/current/VipsForeignSave.html#vips-jpegsave
  JPEG_OPTIONS = { Q: 90, background: 255, strip: true, interlace: true, optimize_coding: true }

  # http://jcupitt.github.io/libvips/API/current/libvips-resample.html#vips-thumbnail
  THUMBNAIL_OPTIONS = { size: :down, linear: false }
  CROP_OPTIONS = { crop: :attention, linear: false }

  def dimensions
    [width, height]
  rescue Vips::Error
    [0, 0]
  end

  def width
    is_rotated? ? image.height : image.width
  rescue Vips::Error
    0
  end

  def height
    is_rotated? ? image.width : image.height
  rescue Vips::Error
    0
  end

  def is_corrupt?
    image.stats
    false
  rescue Vips::Error
    true
  end

  def is_animated?
    is_animated_gif? || is_animated_png?
  end

  def channels
    image.bands
  end

  def colorspace
    image.interpretation
  end

  # @see https://github.com/jcupitt/libvips/wiki/HOWTO----Image-shrinking
  # @see http://jcupitt.github.io/libvips/API/current/Using-vipsthumbnail.md.html
  def preview(width, height)
    output_file = Tempfile.new(["image-preview", ".jpg"])
    resized_image = preview_frame.image.thumbnail_image(width, height: height, **THUMBNAIL_OPTIONS)
    resized_image.jpegsave(output_file.path, **JPEG_OPTIONS)

    MediaFile::Image.new(output_file)
  end

  def crop(width, height)
    output_file = Tempfile.new(["image-crop", ".jpg"])
    resized_image = preview_frame.image.thumbnail_image(width, height: height, **CROP_OPTIONS)
    resized_image.jpegsave(output_file.path, **JPEG_OPTIONS)

    MediaFile::Image.new(output_file)
  end

  def preview_frame
    if is_animated?
      FFmpeg.new(file).smart_video_preview
    else
      self
    end
  end

  def is_animated_gif?
    file_ext == :gif && image.get("n-pages") > 1
  end

  def is_animated_png?
    file_ext == :png && metadata.fetch("PNG:AnimationFrames", 1) > 1
  end

  # https://exiftool.org/TagNames/EXIF.html
  def is_rotated?
    metadata["IFD0:Orientation"].in?(["Rotate 90 CW", "Rotate 270 CW"])
  end

  # @return [Vips::Image] the Vips image object for the file
  def image
    Vips::Image.new_from_file(file.path, fail: true)
  end

  memoize :image, :dimensions, :is_corrupt?, :is_animated_gif?, :is_animated_png?
end