x-govuk/govuk-components

module Helpers
  # This class exists purely to pass to render in format_slim, it doesn't appear
  # to matter what's passed in so long as the first arg responds to #variants
  # and the result responds to #first. Couldn't work out from Rails what the
  # correct obejcts to pass in here are, it's a bit meta.
  class FakeView < ActionView::Base
    def initialize
      super(OpenStruct.new(variants: OpenStruct.new(first: nil)), [], [])
    end

    def variants
      []
    end

    def protect_against_forgery?
      false
    end
  end

  module Formatters
    def block_has_content?(block)
      block.call
    end

    def format_slim(raw, data = nil)
      # FIXME: not sure why when we're several
      #        blocks deep we need to unescape more
      #        than once
      locals = if data
                 eval(data)
               else
                 {}
               end

      template = Slim::Template.new(format: :html) { raw }.render(FakeView.new, **locals)

      beautify(CGI.unescapeHTML(CGI.unescapeHTML(template)))
    end

    def load_data(ruby)
      eval(ruby)
    end

    def format_erb(raw)
      # NOTE: this is many different kinds of bad. Thankfully we're
      #       only using it for documentation purposes and it won't be
      #       displayed by default
      HtmlBeautifier.beautify(
        Slim::ERBConverter.new(
          disable_escape: true,
          disable_capture: true,
          generator: Temple::Generators::RailsOutputBuffer
        )
          .call(raw)
          .gsub(/ _slim_controls\d =/, "=")    # remove _slim_controlsX assignment (where X is an integer)
          .gsub(/do\n\s+%>/, "do %>")          # close blocks on the same line
          .gsub(/%><%/, "%>\n<%")              # ensure ERB tags are on separate lines
          .gsub(/<%= _slim_controls\d %>/, '') # remove _slim_controlsX var display, we've handled it above
          .gsub(/,\n/, ', ')                   # don't leave newlines between args, it breaks indentation
      )
    end

  private

    def beautify(html)
      # All tags except textarea appear to line up correctly when
      # newlines are placed after tags and before closing tags,
      # except textarea which we need to account for manually 😒
      HtmlBeautifier
        .beautify(
          html
            .gsub(">", ">\n")
            .gsub("\<\/", "\n\<\/")
            .gsub(/>\s+<\/textarea>/, "></textarea>")
            .strip
        )
    end
  end
end