module Navigator
  # Renders a HTML menu.
  class Menu
    def self.allowed_methods
      /^(div|section|header|h[1-6]|nav|ul|li|a|img|b|em|s|small|span|strong|sub|sup|form|label|select|option|input|button)$/
    end

    def initialize template, tag: "ul", attributes: {}, activator: Navigator::TagActivator.new, &block
      @template = template
      @tag = Navigator::Tag.new tag, attributes: attributes, activator: activator
      @menu_activator = activator
      @items = []
      instance_eval(&block) if block_given?
    end

    def add name, content = nil, attributes: {}, activator: menu_activator, &block
      tag = Navigator::Tag.new name, content, attributes: attributes, activator: activator
      return items << tag.render unless block_given?

      items << tag.prefix
      items << tag.content
      instance_eval(&block)
      items << tag.suffix
    end

    def link content = nil, url, attributes: {}, activator: menu_activator, &block
      add "a", content, attributes: attributes.merge(href: url), activator: activator, &block
    end

    def image url, alt = nil, attributes: {}, activator: menu_activator
      modified_attributes = attributes.merge src: url, alt: alt
      modified_attributes = modified_attributes.delete_if { |_, value| !value.present? }

      add "img", attributes: modified_attributes, activator: activator
    end

    def item content = nil, url, item_attributes: {}, link_attributes: {}, activator: menu_activator, &block
      modified_item_attributes = item_attributes.clone
      activate_item_attributes! modified_item_attributes, url, activator

      add "li", attributes: modified_item_attributes, activator: activator do
        link content, url, attributes: link_attributes, activator: Navigator::TagActivator.new, &block
      end
    end

    def respond_to? name
      method_allowed?(name) || super(name)
    end

    def method_missing name, *args, &block
      if method_allowed?(name.to_s)
        add(name, *args, &block)
      else
        template.public_send name, *args
      end
    end

    def render
      [tag.prefix, tag.content, items.compact.join(""), tag.suffix].compact * ""
    end

    private

    attr_accessor :template, :tag, :menu_activator, :items

    def method_allowed? name
      self.class.allowed_methods === name
    end

    def activate_item_attributes! attributes, url, activator
      return unless url == activator.search_value
      attributes[activator.target_key] = [attributes[activator.target_key], activator.target_value].compact * " "
    end
  end
end