Erubi template engine test

erubi_deck.rb

# frozen_string_literal: true
require 'erubi'
require 'shield'

class ErubiDeck < Syro::Deck
  include Shield::Helpers

  LAYOUT = 'layout'
  VIEW = 'views/%s.erb'
  DEFAULT_OPTIONS = {
    preamble: false,
    postamble: false,
    ensure: true
  }.freeze

  def session
    req.session
  end

  def partial(template, vars = {}, context = self)
    filename_path = view_path(template)
    opts = { filename: filename_path }
    erubi_cache[template] ||= read_template(filename_path)
    build_dynamic_methods(vars, context, filename_path)
    eval(Erubi::Engine.new(erubi_cache[template], DEFAULT_OPTIONS.merge(opts))
        .src)
  end

  def render(template, vars = {})
    res.html partial(LAYOUT, content: partial(template, vars))
  end

  def either(*segments)
    default { yield } if segments.any? { |segment| consume(segment) }
  end

  private

  def view_path(template)
    format(VIEW, template)
  end

  def read_template(file)
    data = File.open(file, 'rb', &:read)
    data&.force_encoding(Encoding.default_external) if Encoding.default_external
    data
  end

  def build_dynamic_methods(vars, context, filename)
    return if vars.empty?
    vars[:title] = nil unless vars.include?(:title)
    Thread.current[:_erubi_deck_vars] = vars
    code = String.new
    vars.keys.each do |key|
      code << format("def %s; Thread.current[:_erubi_deck_vars][%p]; end\n",
                     key,
                     key)
    end
    context.instance_eval(code, filename, -1)
  end

  def erubi_cache
    Thread.current[:_erubi_deck_cache] ||= {}
  end
end