btrc-hub/backend/app/controllers/preview_controller.rb

class PreviewController < ApplicationController
  def title
    # TODO: # 既知サイトなら決まったフォーマットで title 取得するやぅに．
    return head :unauthorized unless current_user

    url = params[:url]
    return head :bad_request unless url.present?

    html = URI.open(url, open_timeout: 5, read_timeout: 5).read
    doc = Nokogiri::HTML.parse(html)
    title = doc.at('title')&.text&.strip

    render json: { title: title }
  rescue => e
    render json: { error: e.message }, status: :bad_request
  end

  def thumbnail
    # TODO: 既知ドメインであれば指定のアドレスからサムネールを取得するやぅにする．
    return head :unauthorized unless current_user

    url = params[:url]
    return head :bad_request if url.blank?

    path = Rails.root.join('tmp', "thumb_#{ SecureRandom.hex }.png")
    system("node #{ Rails.root }/lib/screenshot.js #{ Shellwords.escape(url) } #{ path }")

    if File.exist?(path)
      image = MiniMagick::Image.open(path)
      image.resize '180x180'
      File.delete(path) rescue nil
      send_file image.path, type: 'image/png', disposition: 'inline'
    else
      render json: { error: 'Failed to generate thumbnail' }, status: :internal_server_error
    end
  end
end