# frozen_string_literal: true

require 'mini_magick'
require 'open3'
require 'tempfile'


class MaterialThumbnailGenerator
  SIZE = '180x180'

  class << self
    def generate! material
      new(material).generate!
    rescue ActiveStorage::FileNotFoundError, ArgumentError, MiniMagick::Error => e
      Rails.logger.warn("Material thumbnail generation skipped: #{ e.class }: #{ e.message }")
      nil
    end
  end

  def initialize material
    @material = material
  end

  def generate!
    @material.thumbnail.purge if @material.thumbnail.attached?
    return unless @material.file.attached?
    return unless image? || video?

    @material.file.blob.open do |file|
      thumbnail = image? ? image_thumbnail(file.path) : video_thumbnail(file.path)
      attach_thumbnail(thumbnail) if thumbnail
    end
  end

  private

  def image? = content_type.start_with?('image/')

  def video? = content_type.start_with?('video/')

  def content_type = @material.file.blob.content_type.to_s

  def image_thumbnail path
    image = MiniMagick::Image.open(path)
    image.resize(SIZE)
    image.format('jpg')
    image
  end

  def video_thumbnail path
    [1, 0].each do |seconds|
      tempfile = Tempfile.new(['material-thumbnail', '.jpg'])
      tempfile.close
      ok = extract_video_frame(path, tempfile.path, seconds)
      next unless ok && File.size?(tempfile.path)

      return image_thumbnail(tempfile.path)
    ensure
      tempfile&.unlink
    end

    nil
  end

  def extract_video_frame input_path, output_path, seconds
    _stdout, stderr, status =
        Open3.capture3('ffmpeg',
                       '-y',
                       '-ss', seconds.to_s,
                       '-i', input_path,
                       '-frames:v', '1',
                       '-f', 'image2',
                       output_path)
    Rails.logger.warn("ffmpeg thumbnail failed: #{ stderr }") unless status.success?
    status.success?
  rescue Errno::ENOENT => e
    Rails.logger.warn("ffmpeg unavailable for material thumbnail: #{ e.message }")
    false
  end

  def attach_thumbnail image
    @material.thumbnail.attach(io: File.open(image.path),
                               filename: 'material-thumbnail.jpg',
                               content_type: 'image/jpeg')
  end
end