asciinema.org/app/controllers/asciicasts_controller.rb

class AsciicastsController < ApplicationController

  before_filter :load_resource, except: [:index]
  before_filter :ensure_authenticated!, only: [:edit, :update, :destroy]

  respond_to :html, :json

  attr_reader :asciicast

  def index
    render locals: {
      page: BrowsePagePresenter.build(params[:category], params[:order],
                                      params[:page])
    }
  end

  def show
    respond_to do |format|
      format.html do
        view_counter.increment(asciicast, cookies)
        render locals: {
          page: AsciicastPagePresenter.build(self, asciicast, current_user, params)
        }
      end

      format.json do
        render json: asciicast
      end

      format.png do
        if asciicast.image_stale?
          with_player_html_file do |html_path|
            image_updater.update(asciicast, html_path)
          end
        end

        redirect_to asciicast.image_url
      end
    end
  end

  def example
    render layout: 'example'
  end

  def edit
    authorize asciicast
  end

  def update
    authorize asciicast

    if asciicast_updater.update(asciicast, update_params)
      redirect_to asciicast_path(asciicast),
                  :notice => 'Asciicast was updated.'
    else
      render :edit
    end
  end

  def destroy
    authorize asciicast

    if asciicast.destroy
      redirect_to profile_path(current_user),
                  :notice => 'Asciicast was deleted.'
    else
      redirect_to asciicast_path(asciicast),
                  :alert => "Oops, we couldn't remove this asciicast. " \
                            "Try again later."
    end
  end

  private

  def load_resource
    @asciicast = Asciicast.find(params[:id])
  end

  def view_counter
    @view_counter ||= ViewCounter.new
  end

  def update_params
    params.require(:asciicast).permit(*policy(asciicast).permitted_attributes)
  end

  def asciicast_updater
    AsciicastUpdater.new
  end

  def image_updater
    AsciicastImageUpdater.new
  end

  def with_player_html_file
    html = render_to_string(
      template: 'asciicasts/screenshot.html.slim',
      layout: 'screenshot',
      locals: { page: BareAsciicastPagePresenter.build(asciicast, params) }
    )

    Dir.mktmpdir do |dir|
      path = "#{dir}/asciicast.html"
      File.open(path, 'w') { |f| f.write(html) }
      yield(path)
    end
  end

end