class PostMetadataFetcher
  def self.fetch raw_url
    uri, = Preview::UrlSafety.validate(raw_url)
    response = Preview::HttpFetcher.fetch(uri.to_s, max_bytes: Preview::ThumbnailFetcher::HTML_MAX_BYTES)
    metadata = Preview::HtmlMetadataExtractor.extract(response)
    document = Nokogiri::HTML.parse(response.body)
    content = -> name { document.at_css("meta[property='#{ name }'], meta[name='#{ name }']")&.[]('content')&.strip.presence }
    duration = content.call('og:video:duration') || content.call('video:duration')
    published = content.call('article:published_time') || content.call('date')
    published_at = Time.zone.parse(published.to_s) if published.present?
    platform_tags = platform_tags(uri)
    { title: metadata[:title],
      thumbnail_base: Preview::KnownSiteExtractor.thumbnail_url(uri) || metadata[:image_url],
      original_created_from: published_at&.iso8601,
      original_created_before: published_at && (published_at + 1.minute).iso8601,
      duration: duration&.to_f&.then { _1.positive? ? (_1 * 1_000).round : nil },
      tags: platform_tags.join(' ') }
  end

  def self.platform_tags uri
    return ['動画', 'YouTube'] if Preview::KnownSiteExtractor.thumbnail_url(uri)
    return ['動画', 'ニコニコ'] if Preview::KnownSiteExtractor.niconico_video_id(uri)

    []
  end
  private_class_method :platform_tags
end