cub8 · Oct 29, 2026 · Oct 25, 2026 · Oct 27, 2026 · Oct 27, 2026 · Oct 27, 2026
diff --git a/Gemfile b/Gemfile
@@ -34,6 +34,7 @@ gem 'omniauth-oauth', '~> 1.2' # OAuth 1.0
 gem 'omniauth-rails_csrf_protection', '~> 2.0' # OAuth CSRF compatibility
 gem 'pundit', '~> 2.5.2' # For roles managements
 gem 'rack-attack', '~> 6.8.0' # For throttling incoming request in authentication
+gem 'rails-i18n', '~> 8.0' # For internationalization [https://github.com/svenfuchs/rails-i18n]
 gem 'rondo_form', '~> 1.0' # For nested forms
 gem 'rqrcode', '~> 3.0' # For generating QR codes
 gem 'tzinfo-data', '~> 1', platforms: %i[windows jruby] # Windows does not include zoneinfo files, so bundle the tzinfo-data gem

diff --git a/Gemfile.lock b/Gemfile.lock
@@ -321,6 +321,9 @@ GEM
     rails-html-sanitizer (1.7.1)
       loofah (~> 2.25, >= 2.25.2)
       nokogiri (>= 1.15.7, != 1.16.7, != 1.16.6, != 1.16.5, != 1.16.4, != 1.16.3, != 1.16.2, != 1.16.1, != 1.16.0.rc1, != 1.16.0)
+    rails-i18n (8.1.0)
+      i18n (>= 0.7, < 2)
+      railties (>= 8.0.0, < 9)
     railties (8.1.3.1)
       actionpack (= 8.1.3.1)
       activesupport (= 8.1.3.1)
@@ -478,6 +481,7 @@ DEPENDENCIES
   pundit (~> 2.5.2)
   rack-attack (~> 6.8.0)
   rails (~> 8.1.3.1)
+  rails-i18n (~> 8.0)
   rondo_form (~> 1.0)
   rqrcode (~> 3.0)
   rubocop (~> 1.84)
@@ -615,6 +619,7 @@ CHECKSUMS
   rails (8.1.3.1) sha256=ccd11a36bfc171bf9c66d585d14c0ece91c0c9dde840aae60c0118d6f5c9c52a
   rails-dom-testing (2.3.0) sha256=8acc7953a7b911ca44588bf08737bc16719f431a1cc3091a292bca7317925c1d
   rails-html-sanitizer (1.7.1) sha256=e797a7c9b01e567307e317c576b49ab4168017e63eea4dba9ce3cb587e2f22c2
+  rails-i18n (8.1.0) sha256=52d5fd6c0abef28d84223cc05647f6ae0fd552637a1ede92deee9545755b6cf3
   railties (8.1.3.1) sha256=2388a232579a00cefea4487de66c8553c3408c1300abdc6cf1799d86ffb04487
   rainbow (3.1.1) sha256=039491aa3a89f42efa1d6dec2fc4e62ede96eb6acd95e52f1ad581182b79bc6a
   rake (13.3.1) sha256=8c9e89d09f66a26a01264e7e3480ec0607f0c497a861ef16063604b1b08eb19c

diff --git a/app/components/shared/header_component.html.haml b/app/components/shared/header_component.html.haml
@@ -1,12 +1,12 @@
 %header.gh-topbar
-  = link_to home_path, class: 'gh-topbar-logo', 'aria-label': 'Gamification Hub, start' do
+  = link_to home_path, class: 'gh-topbar-logo', 'aria-label': t('layouts.header.home') do
     = image_tag 'logo.png', alt: ''
     %span.gh-topbar-logo-word Gamification Hub
 
   - if group_chrome
     %button.gh-group-switcher{ type: 'button',
                     data: { action: 'menu#open', menu_id_param: 'gh-group-switcher' },
-                    'aria-label': "Grupa #{group_chrome.name}, zmień grupę" }
+                    'aria-label': t('layouts.header.switch_group', name: group_chrome.name) }
       = render 'layouts/group_thumb', story_group: group_chrome.story_group, size: nil
       %span.gh-group-switcher-name= group_chrome.name
       %i.fa-solid.fa-chevron-down{ 'aria-hidden': 'true' }
@@ -17,21 +17,21 @@
     - purse = group_chrome.student_membership
     = link_to story_group_student_currency_transactions_path(group_chrome.story_group, purse),
       class: 'gh-balance-button',
-      title: "#{purse.current_currency} do wydania, #{purse.total_currency} zebrane łącznie",
-      'aria-label': "Masz #{purse.current_currency} do wydania, pokaż historię waluty" do
+      title: t('layouts.header.balance_title', balance: purse.current_currency, total: purse.total_currency),
+      'aria-label': t('layouts.header.balance_label', balance: purse.current_currency) do
       = render 'layouts/currency_token', story_group: group_chrome.story_group, size: 32
       %span
         %b= purse.current_currency
-        %small do wydania
+        %small= t('layouts.header.to_spend')
 
   = link_to new_join_path, class: 'gh-btn gh-btn--secondary gh-btn--small gh-topbar-join-link',
     data: { turbo_frame: 'modal' } do
     %i.fa-solid.fa-plus
-    %span Dołącz do grupy
+    %span= t('layouts.header.join')
 
   %button.gh-icon-button.gh-topbar-theme-toggle{ type: 'button',
                                   data: { action: 'theme#toggle' },
-                                  'aria-label': 'Przełącz motyw' }
+                                  'aria-label': t('layouts.theme.toggle') }
     %i.fa-solid.fa-moon.gh-theme-icon-moon
     %i.fa-solid.fa-sun.gh-theme-icon-sun
 
@@ -44,6 +44,6 @@
 
   %button.gh-avatar-button{ type: 'button',
                     data: { action: 'menu#open', menu_id_param: 'gh-account-menu' },
-                    'aria-label': "Konto: #{user.full_name}" }
+                    'aria-label': t('layouts.header.account', name: user.full_name) }
     %span.gh-avatar.gh-octagon-clip{ 'data-gh-h': helpers.gh_avatar_hue(user.full_name), 'aria-hidden': 'true' }
       = helpers.gh_initials(user.full_name)
diff --git a/app/components/shared/header_component.rb b/app/components/shared/header_component.rb
@@ -20,8 +20,8 @@ def unread_count
   end
 
   def bell_label
-    return 'Powiadomienia' if unread_count.zero?
+    return t('layouts.header.notifications') if unread_count.zero?
 
-    "Powiadomienia, #{unread_count} #{helpers.gh_plural(unread_count, 'nowe', 'nowe', 'nowych')}"
+    t('layouts.header.notifications_unread', count: unread_count)
   end
 end
diff --git a/app/components/shared/sidebar_component.html.haml b/app/components/shared/sidebar_component.html.haml
@@ -1,6 +1,6 @@
 %aside.gh-sidebar{ class: ('gh-sidebar--collapsed' if collapsed),
               data: { sidebar_target: 'sidebar' } }
-  %nav.gh-sidebar-nav.gh-sidebar-nav--primary{ 'aria-label': 'Główna' }
+  %nav.gh-sidebar-nav.gh-sidebar-nav--primary{ 'aria-label': t('layouts.sidebar.main') }
     - nav_items.each do |item|
       = link_to item.path, class: "gh-sidebar-link #{'gh-sidebar-link--active' if current?(item.path)}",
         title: item.label, 'aria-current': ('page' if current?(item.path)) do
@@ -10,7 +10,7 @@
   - if group_chrome
     = render 'layouts/deck', chrome: group_chrome, current_path: current_path
   - elsif groups.any?
-    %p.gh-sidebar-section-label Twoje grupy
+    %p.gh-sidebar-section-label= t('layouts.sidebar.your_groups')
     .gh-sidebar-group-list
       - groups.each do |story_group|
         = link_to story_group_path(story_group), class: 'gh-sidebar-group-list-item', title: story_group.name do

diff --git a/app/components/shared/sidebar_component.rb b/app/components/shared/sidebar_component.rb
@@ -25,7 +25,7 @@ def groups
   end
 
   def role_label(story_group)
-    StoryGroupsListing::ROLE_LABELS[role_for(story_group)]
+    t("story_groups.listing.roles.#{role_for(story_group)}")
   end
 
   def role_for(story_group)
@@ -44,7 +44,7 @@ def current?(path)
   end
 
   def toggle_label
-    collapsed ? 'Rozwiń' : 'Zwiń panel'
+    collapsed ? t('layouts.sidebar.expand') : t('layouts.sidebar.collapse')
   end
 
   def toggle_icon

diff --git a/app/components/shared/tab_bar_component.html.haml b/app/components/shared/tab_bar_component.html.haml
@@ -1,4 +1,4 @@
-%nav.gh-mobile-tabbar{ 'aria-label': 'Nawigacja' }
+%nav.gh-mobile-tabbar{ 'aria-label': t('layouts.tab_bar.label') }
   - items.each do |item|
     - on = item.current?(current_path)
     = link_to item.path, class: "gh-mobile-tab #{'gh-mobile-tab--active' if on}",
@@ -10,4 +10,4 @@
   %button.gh-mobile-tab{ type: 'button',
                   data: { action: 'menu#open', menu_id_param: 'gh-more-sheet' } }
     %i.fa-solid.fa-ellipsis
-    %span Więcej
+    %span= t('shared.actions.more')
diff --git a/app/controllers/account_setups_controller.rb b/app/controllers/account_setups_controller.rb
@@ -12,7 +12,7 @@ def update
     @current_user.first_login = false
 
     if @current_user.save(context: :account_setup)
-      redirect_to home_path, notice: 'Pomyślnie skonfigurowano konto.'
+      redirect_to home_path, notice: t('account_setups.flash.done')
     else
       @current_user.first_login = true
       render :edit, status: :unprocessable_content

diff --git a/app/controllers/activity_group_templates_controller.rb b/app/controllers/activity_group_templates_controller.rb
@@ -11,7 +11,9 @@ class ActivityGroupTemplatesController < ApplicationController
   def new
     @activity_group_template = @story_group.activity_group_templates.build
 
-    @activity_group_template.categories.build(didactic_description: 'Obecność', reward: 2, position: 0)
+    @activity_group_template.categories.build(didactic_description: t('activity_group_templates.default_category'),
+                                              reward:               2,
+                                              position:             0,)
     @activity_group_template.categories.build(reward: 1, position: 1)
   end
 
@@ -28,7 +30,8 @@ def create
 
     if @activity_group_template.save(context: :settings)
       redirect_to story_group_activity_groups_path(@story_group),
-                  notice: "Utworzono szablon „#{@activity_group_template.base_name}”.", status: :see_other
+                  notice: t('activity_group_templates.flash.created', name: @activity_group_template.base_name),
+                  status: :see_other
     else
       render :new, status: :unprocessable_content
     end
@@ -39,7 +42,7 @@ def update
 
     if @activity_group_template.save(context: :settings)
       redirect_to story_group_activity_groups_path(@story_group),
-                  notice: 'Zapisano szablon. Nowe arkusze dostaną te kategorie.', status: :see_other
+                  notice: t('activity_group_templates.flash.updated'), status: :see_other
     else
       @sheet_names = sheet_names_for(@activity_group_template)
       render :edit, status: :unprocessable_content
@@ -51,7 +54,7 @@ def destroy
     @activity_group_template.soft_delete!
 
     redirect_outside_turbo_frame story_group_activity_groups_path(@story_group),
-                                 notice: "Usunięto szablon „#{name}”. Utworzone z niego arkusze zostają."
+                                 notice: t('activity_group_templates.flash.destroyed', name: name)
   end
 
   private

diff --git a/app/controllers/activity_groups_controller.rb b/app/controllers/activity_groups_controller.rb
@@ -43,7 +43,7 @@ def update
 
     if @activity_group.save(context: :settings)
       redirect_to story_group_activity_groups_path(@story_group),
-                  notice: "Zapisano ustawienia arkusza #{@activity_group.name}.", status: :see_other
+                  notice: t('activity_groups.flash.updated', name: @activity_group.name), status: :see_other
     else
       render :edit, status: :unprocessable_content
     end
@@ -54,8 +54,7 @@ def destroy
     @activity_group.soft_delete!
 
     redirect_outside_turbo_frame story_group_activity_groups_path(@story_group),
-                                 notice: "Usunięto arkusz #{name}. " \
-                                         'Przyznane nagrody zostają w historii studentów.'
+                                 notice: t('activity_groups.flash.destroyed', name: name)
   end
 
   private
@@ -87,9 +86,9 @@ def bulk_count
   end
 
   def created_notice(sheets)
-    return "Utworzono: #{sheets.first.name}." if sheets.one?
+    return t('activity_groups.flash.created_one', name: sheets.first.name) if sheets.one?
 
-    "Utworzono: #{sheets.first.name} – #{sheets.last.name}."
+    t('activity_groups.flash.created_many', first: sheets.first.name, last: sheets.last.name)
   end
 
   def columns_changed?

diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
@@ -2,6 +2,7 @@
 
 class ApplicationController < ActionController::Base
   include Pundit::Authorization
+  include Localization
   include Authentication
   include Sidebar
   include StatusRedirects

diff --git a/app/controllers/auth/passwordless_controller.rb b/app/controllers/auth/passwordless_controller.rb
@@ -30,7 +30,7 @@ def verify
     token = params.expect(:token)
     login_token = LoginToken.find_by_token(token)
 
-    return redirect_to login_path, alert: 'Nieprawidłowy token' if login_token.nil? || login_token.expired?
+    return redirect_to login_path, alert: t('auth.flash.invalid_token') if login_token.nil? || login_token.expired?
 
     user = login_token.user
     user.consume_login_token!
@@ -61,7 +61,7 @@ def create
     session[:pending_login_email]   = email
     session[:pending_login_sent_at] = Time.current.to_i
 
-    notice = 'Wysłaliśmy nowy link. Poprzedni już nie działa.' if resend
+    notice = t('auth.flash.resent') if resend
     redirect_to auth_passwordless_inbox_path, notice: notice
   end
 

diff --git a/app/controllers/auth/usos_controller.rb b/app/controllers/auth/usos_controller.rb
@@ -16,9 +16,9 @@ def create
 
     sign_in_and_redirect(user)
   rescue InvalidProviderError
-    redirect_to root_path, alert: 'Nieprawidłowy dostawca logowania.'
+    redirect_to root_path, alert: t('auth.flash.invalid_provider')
   rescue Providers::InvalidAuthError
-    redirect_to root_path, alert: 'Nieprawidłowa próba autoryzacji.'
+    redirect_to root_path, alert: t('auth.flash.invalid_auth')
   end
 
   private

diff --git a/app/controllers/badges_controller.rb b/app/controllers/badges_controller.rb
@@ -32,7 +32,7 @@ def create
     @badge = @story_group.badges.build(badge_params)
 
     if @badge.save
-      redirect_to story_group_badges_path(@story_group), notice: "Dodano odznakę „#{@badge.name}”."
+      redirect_to story_group_badges_path(@story_group), notice: t('badges.flash.created', name: @badge.name)
     else
       set_shelf
       render :new, status: :unprocessable_content
@@ -41,7 +41,7 @@ def create
 
   def update
     if @badge.update(badge_params)
-      redirect_to story_group_badges_path(@story_group), notice: "Zapisano odznakę „#{@badge.name}”."
+      redirect_to story_group_badges_path(@story_group), notice: t('badges.flash.updated', name: @badge.name)
     else
       set_shelf
       render :edit, status: :unprocessable_content
@@ -53,8 +53,7 @@ def destroy
     @badge.soft_delete!
 
     redirect_outside_turbo_frame story_group_badges_path(@story_group),
-                                 notice: "Usunięto odznakę „#{name}”. Studenci, " \
-                                         'którzy ją mają, zachowują ją w historii.'
+                                 notice: t('badges.flash.destroyed', name: name)
   end
 
   private

diff --git a/app/controllers/concerns/auth/sign_in.rb b/app/controllers/concerns/auth/sign_in.rb
@@ -10,7 +10,7 @@ def sign_in_and_redirect(user)
     reset_session
     session[:user_id] = user.id
 
-    redirect_to after_login_path(return_to), notice: 'Zalogowano pomyślnie.'
+    redirect_to after_login_path(return_to), notice: t('auth.flash.signed_in')
   end
 
   def after_login_path(path)

diff --git a/app/controllers/concerns/authentication.rb b/app/controllers/concerns/authentication.rb
@@ -21,7 +21,7 @@ def authenticate!
     return if @current_user
 
     store_return_path
-    redirect_to login_path, alert: 'Zaloguj się, aby kontynuować.'
+    redirect_to login_path, alert: t('application.flash.log_in_first')
   end
 
   def store_return_path

diff --git a/app/controllers/concerns/localization.rb b/app/controllers/concerns/localization.rb
@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+module Localization
+  extend ActiveSupport::Concern
+
+  LOCALE_COOKIE = :locale
+
+  included do
+    around_action :switch_locale
+  end
+
+  protected
+
+  # A block keeps the locale from leaking into the next request served by the same thread.
+  def switch_locale(&)
+    I18n.with_locale(requested_locale, &)
+  end
+
+  def requested_locale
+    [cookies[LOCALE_COOKIE], browser_locale].find { |locale| available_locale?(locale) } || I18n.default_locale
+  end
+
+  # "en-US,en;q=0.9,pl;q=0.8" -> "en". Browsers list languages in order of preference.
+  def browser_locale
+    request.headers['Accept-Language'].to_s.split(',')
+           .map { |entry| entry.strip.first(2).downcase }
+           .find { |locale| available_locale?(locale) }
+  end
+
+  def available_locale?(locale)
+    I18n.available_locales.map(&:to_s).include?(locale.to_s)
+  end
+end
diff --git a/app/controllers/concerns/logged_user_redirector.rb b/app/controllers/concerns/logged_user_redirector.rb
@@ -2,6 +2,6 @@
 
 module LoggedUserRedirector
   def redirect_logged_user
-    redirect_to root_path, alert: 'Jesteś już zalogowany.' if @current_user
+    redirect_to root_path, alert: t('application.flash.already_signed_in') if @current_user
   end
 end
diff --git a/app/controllers/concerns/status_redirects.rb b/app/controllers/concerns/status_redirects.rb
@@ -4,10 +4,10 @@ module StatusRedirects
   protected
 
   def record_not_found
-    redirect_to root_path, alert: 'Nie znaleziono.'
+    redirect_to root_path, alert: t('application.flash.not_found')
   end
 
   def not_authorized
-    redirect_to root_path, alert: 'Nie znaleziono.'
+    redirect_to root_path, alert: t('application.flash.not_found')
   end
 end
diff --git a/app/controllers/currency_adjustments_controller.rb b/app/controllers/currency_adjustments_controller.rb
@@ -38,8 +38,8 @@ def set_presentation
   end
 
   def notice_for(form)
-    verb = form.positive? ? 'Dodano' : 'Odjęto'
+    key = form.positive? ? 'added' : 'taken'
 
-    "#{verb} #{form.value}. Saldo: #{@student.reload.current_currency}."
+    t("currency_adjustments.flash.#{key}", value: form.value, balance: @student.reload.current_currency)
   end
 end
diff --git a/app/controllers/currency_transactions_controller.rb b/app/controllers/currency_transactions_controller.rb
@@ -31,7 +31,7 @@ def set_student
   end
 
   def ledger_kind
-    kinds = CurrencyLedger::KINDS.map(&:first).compact
+    kinds = CurrencyLedger::KINDS.compact
     kinds.include?(params[:kind]) ? params[:kind] : nil
   end
 end