module GovukPublishingComponents
  module Presenters
    # @private
    # Only used by the related_navigation component
    class RelatedNavigationHelper
      MAX_SECTION_LENGTH = 5
      DEFINED_SECTIONS = %w(
        related_guides
        topics
        collections
        topical_events
        world_locations
        statistical_data_sets
      ).freeze
      WORLD_LOCATION_SPECIAL_CASES = {
        "UK Mission to the European Union" => "uk-mission-to-the-eu",
      }.freeze

      def initialize(options = {})
        @content_item = options.fetch(:content_item) { raise ArgumentError, "missing argument: content_item" }
        @context = options.fetch(:context, nil)
      end

      def related_navigation
        case @context.try(:to_sym)
        when :sidebar
          {
            "related_items" => related_items,
            "related_guides" => related_guides,
            "collections" => related_document_collections,
          }
        when :footer
          {
            "topics" => related_topics,
            "topical_events" => related_topical_events,
            "world_locations" => related_world_locations,
            "statistical_data_sets" => related_statistical_data_sets,
            "related_external_links" => related_external_links,
            "related_contacts" => related_contacts,
          }
        else
          {
            "related_items" => related_items,
            "related_guides" => related_guides,
            "collections" => related_document_collections,
            "topics" => related_topics,
            "topical_events" => related_topical_events,
            "world_locations" => related_world_locations,
            "statistical_data_sets" => related_statistical_data_sets,
            "related_external_links" => related_external_links,
            "related_contacts" => related_contacts,
          }
        end
      end

      def construct_section_heading(section_title)
        unless section_title === "related_items"
          I18n.t("components.related_#{@context}_navigation." + section_title,
                 default: [
                   I18n.t("components.related_navigation." + section_title),
                   section_title.tr("_", " "),
                 ])
        end
      end

      def section_css_class(css_class, section_title, link = {}, link_is_inline = false)
        css_classes = [css_class]
        css_classes << "#{css_class}--#{@context}" unless @context.nil?
        css_classes << "#{css_class}--inline" if link_is_inline

        unless DEFINED_SECTIONS.include?(section_title) || link.fetch(:finder, false)
          css_classes << " #{css_class}--other"
        end

        css_classes.join(" ")
      end

      def section_data_track_count(section_title)
        String(@context || "sidebar") + String(section_title).camelcase
      end

      def section_heading_level
        @context == :footer ? "h2" : "h3"
      end

      def calculate_section_link_limit(links)
        links.length == MAX_SECTION_LENGTH + 1 ? MAX_SECTION_LENGTH + 1 : MAX_SECTION_LENGTH
      end

      def remaining_link_count(links)
        links.length - MAX_SECTION_LENGTH
      end

      def related_navigation?
        related_navigation.flat_map(&:last).any?
      end

      def t_locale(content, options = {})
        # Check if the content string has a translation
        content_translation_available = translation_present?(content)

        # True, return locale
        this_locale = I18n.locale if content_translation_available
        # If false, return default locale
        this_locale = I18n.default_locale unless content_translation_available

        # Check if default string passed in
        if options[:default].present?
          # Check if the default string has a translation
          default_translation_available = translation_present?(options[:default])
          # If true, return locale
          this_locale = I18n.locale if default_translation_available
          # If false, return default_locale
          this_locale = I18n.default_locale unless default_translation_available
        end

        this_locale
      end

      def t_lang(content, options = {})
        locale = t_locale(content, options)
        "lang=#{locale}" unless locale.eql?(I18n.locale)
      end

      def t_locale_check(locale)
        locale.presence unless locale.to_s.eql?(I18n.locale.to_s)
      end

    private

      def translation_present?(content)
        default_string = "This is a string to act as a default for the `I18n.translate` method. Comparing the result reveals if there is a translation in the i18n files."
        I18n.translate(
          content,
          default: default_string,
          fallback: false,
        ) != default_string
      end

      def related_items
        related_quick_links = content_item_details_for("quick_links")

        if related_quick_links.any?
          related_quick_links + related_mainstream_content
        else
          content_item_links_for("ordered_related_items") + related_mainstream_content
        end
      end

      def related_world_locations
        content_item_links_for("world_locations")
          .map do |link|
            slug = WORLD_LOCATION_SPECIAL_CASES[link[:text]] || link[:text].parameterize
            link.merge(path: "/world/#{slug}/news")
          end
      end

      def related_statistical_data_sets
        content_item_links_for("related_statistical_data_sets", only: "statistical_data_set")
      end

      def related_taxons
        content_item_links_for("taxons", only: "taxon")
      end

      def related_topics
        if related_legacy_topics.any?
          related_legacy_topics
        elsif related_taxons.any?
          related_taxons
        else
          []
        end
      end

      def related_legacy_topics
        mainstream_browse_page_links = content_item_links_for("mainstream_browse_pages", only: "mainstream_browse_page")
        topic_links = content_item_links_for("topics", only: "topic")

        mainstream_browse_page_links + topic_links.find_all do |topic_link|
          mainstream_browse_page_links.none? do |mainstream_browse_page_link|
            mainstream_browse_page_link[:text] == topic_link[:text]
          end
        end
      end

      def related_topical_events
        content_item_links_for("topical_events", only: "topical_event")
      end

      def related_contacts
        content_item_links_for("related", only: "contact")
      end

      def related_external_links
        content_item_details_for("external_related_links")
      end

      def related_mainstream_content
        return [] unless detailed_guide?

        content_item_links_for("related_mainstream_content")
      end

      def related_guides
        return [] unless detailed_guide?

        content_item_links_for("related_guides")
      end

      def related_document_collections
        content_item_links_for("document_collections", only: "document_collection")
      end

      def detailed_guide?
        @content_item["document_type"] == "detailed_guide"
      end

      def content_item_details_for(key)
        Array(@content_item.dig("details", key))
          .map { |link| { path: link["url"], text: link["title"], rel: "external" } }
      end

      def content_item_links_for(key, only: nil)
        links = Array(@content_item.dig("links", key))

        if key == "taxons"
          links = links.find_all { |link| link["phase"] == "live" }
        end

        if only.present?
          links = links.find_all { |link| link["document_type"] == only }
        end

        links.map { |link|
          {
            path: link["base_path"],
            text: link["title"],
            locale: link["locale"],
          }
        }
      end
    end
  end
end