class ActiveStorage::Analyzer::VideoAnalyzer

def self.accept?(blob)
  blob.video?
end

def angle
  Integer(tags["rotate"]) if tags["rotate"]
end

def audio?
  audio_stream.present?
end

def audio_stream
  @audio_stream ||= streams.detect { |stream| stream["codec_type"] == "audio" } || {}
end

def computed_height
  if encoded_width && display_height_scale
    encoded_width * display_height_scale
  end
end

def container
  probe["format"] || {}
end

def display_aspect_ratio
  if descriptor = video_stream["display_aspect_ratio"]
    if terms = descriptor.split(":", 2)
      numerator   = Integer(terms[0])
      denominator = Integer(terms[1])
      [numerator, denominator] unless numerator == 0
    end
  end
end

def display_height_scale
  @display_height_scale ||= Float(display_aspect_ratio.last) / display_aspect_ratio.first if display_aspect_ratio
end

def duration
  duration = video_stream["duration"] || container["duration"]
  Float(duration) if duration
end

def encoded_height
  @encoded_height ||= Float(video_stream["height"]) if video_stream["height"]
end

def encoded_width
  @encoded_width ||= Float(video_stream["width"]) if video_stream["width"]
end

def ffprobe_path
  ActiveStorage.paths[:ffprobe] || "ffprobe"
end

def height
  if rotated?
    encoded_width
  else
    computed_height || encoded_height
  end
end

def metadata
  { width: width, height: height, duration: duration, angle: angle, display_aspect_ratio: display_aspect_ratio, audio: audio?, video: video? }.compact
end

def probe
  @probe ||= download_blob_to_tempfile { |file| probe_from(file) }
end

def probe_from(file)
  instrument(File.basename(ffprobe_path)) do
    IO.popen([ ffprobe_path,
      "-print_format", "json",
      "-show_streams",
      "-show_format",
      "-v", "error",
      file.path
    ]) do |output|
      JSON.parse(output.read)
    end
  end
rescue Errno::ENOENT
  logger.info "Skipping video analysis because ffprobe isn't installed"
  {}
end

def rotated?
  angle == 90 || angle == 270
end

def streams
  probe["streams"] || []
end

def tags
  @tags ||= video_stream["tags"] || {}
end

def video?
  video_stream.present?
end

def video_stream
  @video_stream ||= streams.detect { |stream| stream["codec_type"] == "video" } || {}
end

def width
  if rotated?
    computed_height || encoded_height
  else
    encoded_width
  end
end