application_helper.rb

module ApplicationHelper
  def tenant_name
    tenant_configuration.tenant_name
  end

  def full_title(page_title)
    base_title = "#{app_display_name} Dashboard"
    if page_title.empty?
      base_title
    else
      "#{base_title} | #{page_title}".html_safe
    end
  end

  def app_display_name
    tenant_configuration.display_name
  end

  def participant_login_link
    tenant_configuration.disc_url
  end

  def analytics
    render("layouts/analytics") if Rails.env.production?
  end

  def display_header?
    HeaderDisplayPolicy.call(controller: controller_name, action: action_name)
  end

  def time_from(date)
    from_time = DateTime.parse(date)
    distance_of_time_in_words(from_time, DateTime.now) << " ago"
  end

  def support_email_link
    link_to(t("support"), "mailto:#{support_email}")
  end

  def terms_link
    link_to(t("terms"), page_path("terms"))
  end

  def website_link
    link_to(website_link_text, website_url, target: "_blank")
  end

  def copyright
    copy = "&copy; #{t("copyright")} #{copyright_agencies} #{copyright_period}"
    copy.html_safe
  end

  def complete_on_device
    t("task.complete_on_device",
      app_name: app_display_name,
      ios: ios_link,
      android: android_link
     ).html_safe
  end

  def current_language_flag
    language = Language.all.select { |l| l.code == I18n.locale.to_s }.first
    image_tag(language.flag, alt: language.label)
  end

  private

  def website_link_text
    strip_www(URI.parse(website_url).host)
  end

  def strip_www(host)
    host.start_with?("www.") ? host[4..-1] : host
  end

  def website_url
    tenant_configuration.website
  end

  def support_email
    tenant_configuration.support_email
  end

  def copyright_agencies
    tenant_configuration.copyright
  end

  def copyright_period
    "2012-#{Time.now.year}"
  end

  def ios_link
    link_to("iOS", tenant_configuration.ios_url, target: "_blank")
  end

  def android_link
    link_to("Android", tenant_configuration.android_url, target: "_blank")
  end

  def tenant_configuration
    Hashie::Mash.new(Crowdlab.tenants[Crowdlab.tenant])
  end
end

application_helper_spec.rb

require "spec_helper"

describe ApplicationHelper do
  # ...
  describe "#display_header?" do
    it "creates a new HeaderDisplayPolicy instance and calls #call" do
      args = { controller: helper.controller_name, action: helper.action_name }
      policy_double = double
      allow(HeaderDisplayPolicy).to receive(:new).with(args)
        .and_return(policy_double)
      expect(policy_double).to receive(:call)
      helper.display_header?
    end
  end
  # ...
end

header_display_policy.rb

class HeaderDisplayPolicy
  def self.call(controller:, action:)
    new(controller: controller, action: action).call
  end

  def initialize(controller:, action:)
    @controller = controller
    @action = action
  end

  def call
    projects_index? || controller_in_whitelist?
  end

  private

  attr_reader :controller, :action

  def projects_index?
    controller == "projects" && action == "index"
  end

  def controller_in_whitelist?
    white_list.include?(controller)
  end

  def white_list
    %w(sessions users passwords pages joins)
  end
end

header_display_policy_spec.rb

require "spec_helper"

describe HeaderDisplayPolicy do
  describe ".call" do
    it "creates a new instance and calls #call" do
      args = { controller: "projects", action: "index" }
      policy_double = double
      allow(HeaderDisplayPolicy).to receive(:new).with(args)
        .and_return(policy_double)
      expect(policy_double).to receive(:call)
      HeaderDisplayPolicy.call(args)
    end
  end

  describe "#call" do
    context "when @controller is 'projects' and @action is 'index'" do
      it "returns true" do
        result = HeaderDisplayPolicy.new(controller: "projects",
                                         action: "index").call
        expect(result).to eq(true)
      end
    end

    context "when @controller is in the white list" do
      it "returns true" do
        result = HeaderDisplayPolicy.new(controller: "sessions",
                                         action: "index").call
        expect(result).to eq(true)
      end
    end
  end
end