infer locale from params, then cookies, then Accept-Language header

Gemfile

@@ -48,6 +48,8 @@ gem "carrierwave", "~> 0.5.8"
 
 gem "parallel", "~> 0.5.17"
 
+gem "http_accept_language", :git => "git://github.com/iain/http_accept_language.git"
+
 group :development do
   gem "bullet", "~> 4.1.5"
 end

Gemfile.lock

@@ -4,6 +4,12 @@ GIT
   specs:
     eventmachine (1.0.0.beta.4)
 
+GIT
+  remote: git://github.com/iain/http_accept_language.git
+  revision: 7738e45ba154015597fca749b7d0257861c14a02
+  specs:
+    http_accept_language (2.0.0.pre)
+
 GIT
   remote: git://github.com/igrigorik/em-http-request.git
   revision: ce50f322ce08d43a4a747cf333ea576765d764c4
@@ -254,6 +260,7 @@ DEPENDENCIES
   fog (~> 1.1.2)
   haml (~> 3.0.18)
   hoptoad_notifier
+  http_accept_language!
   jammit (~> 0.5.3)
   memcache-client (~> 1.8.5)
   mini_magick (~> 3.4)

app/controllers/application_controller.rb

@@ -19,11 +19,12 @@ class ApplicationController < ActionController::Base
     true
   end
   
-  # This locale-inferrence method is designed for debugging. Once we're ready
-  # for production, we'll probably start inferring from domain.
   def infer_locale
-    inference = params[:locale]
+    return params[:locale] if valid_locale?(params[:locale])
-    inference if inference && I18n.available_locales.include?(inference.to_sym)
+    return cookies[:locale] if valid_locale?(cookies[:locale])
+    Rails.logger.debug "Preferred languages: #{http_accept_language.user_preferred_languages}"
+    http_accept_language.language_region_compatible_from(I18n.available_locales.map(&:to_s)) ||
+      I18n.default_locale
   end
   
   def localized_fragment_exist?(key)
@@ -54,5 +55,9 @@ class ApplicationController < ActionController::Base
   def user_is?(user)
     user_signed_in? && user == current_user
   end
+  
+  def valid_locale?(locale)
+    locale && I18n.available_locales.include?(locale.to_sym)
+  end
 end
 

config/locales/en-MEEP.yml

@@ -1,4 +1,4 @@
-en-meep:
+en-MEEP:
   app_name: Dreep to Impreep
   organization_name: OpenMeep
   your_items: Your Meeps

config/locales/will_paginate.en-MEEP.yml

@@ -1,4 +1,4 @@
-en-meep:
+en-MEEP:
   will_paginate:
     previous_label: "← Preevious"
     next_label: "Neext →"