Breadcrumbs, OO version

breadcrumbs.rb

# typed: false
# frozen_string_literal: true

require 'json'

module PublicLaw
  # Represents a breadcrumb trail on a page.
  class Breadcrumbs
    include ActionView::Helpers
    extend T::Sig

    JSON_PREFIX = "<script type=\"application/ld+json\">\n"
    JSON_SUFFIX = "\n</script>\n"

    HTML_PREFIX = "<nav aria-label=\"breadcrumb\">\n<ol class=\"breadcrumb\">"
    HTML_SUFFIX = "</ol>\n</nav>"

    Links = T.type_alias { T::Array[T::Hash[Symbol, String]] }


    sig {params(title: String, location: String).returns(Breadcrumbs)}
    def initialize(title:, location:)
      raise 'Title is blank' if title.blank?
      raise 'Location is blank' if location.blank?

      @all_but_last_item = T.let([], Links)
      @last_item = T.let({ title: sanitize(title), location: location }, T::Hash[Symbol, String])

      self
    end


    sig {params(title: String, location: String).returns(Breadcrumbs)}
    def add(title:, location:)
      raise 'Title is blank' if title.blank?
      raise 'Location is blank' if location.blank?

      @all_but_last_item << @last_item
      @last_item = { title: sanitize(title), location: location }

      self
    end


    sig {returns(String)}
    def to_s
      to_html
    end



    private


    sig {returns(String)}
    def to_html
      (microdata_json + "\n" + html_list).html_safe
    end


    sig {returns(String)}
    def microdata_json
      microdata = {
        '@context'        => 'http://schema.org',
        '@type'           => 'BreadcrumbList',
        'itemListElement' => list_elements(@all_but_last_item + [@last_item]),
      }
      JSON_PREFIX + microdata.to_json + JSON_SUFFIX
    end


    sig {returns(String)}
    def html_list
      HTML_PREFIX + "\n" + list_items_html + HTML_SUFFIX + "\n"
    end


    sig {returns(String)}
    def list_items_html
      '  ' + list_items.join("\n  ") + "\n"
    end

    #
    # Create HTML <li> elements from the Links. All but
    # the last should be hyperlinks.
    #
    sig {returns(T::Array[String])}
    def list_items
      @all_but_last_item
        .map { |l| "<li class=\"breadcrumb-item\"><a href=\"#{l[:location]}\">#{l[:title]}</a></li>" }
        .push(final_list_item)
    end


    sig {returns(String)}
    def final_list_item
      "<li class=\"breadcrumb-item active\" aria-current=\"page\">#{@last_item.fetch(:title)}</li>"
    end

    sig {params(links: Links).returns(T::Array[T::Hash[String, T.untyped]])}
    def list_elements(links)
      list_elements = []
      links.each_index do |index|
        list_elements << {
          '@type'    => 'ListItem',
          'position' => index + 1,
          'item'     => {
            '@id'  => links[index].fetch(:location),
            'name' => links[index].fetch(:title),
          },
        }
      end
      list_elements
    end
  end
end