add a locale negotiator that uses Accept-Language

2 files changed, 33 insertions, 1 deletions

diff --git a/development.ini b/development.ini
index a93c838..15250c4 100644
--- a/development.ini
+++ b/development.ini
@@ -27,6 +27,7 @@ retry.attempts = 3
 email.from = fietsboek@kingdread.de
 email.smtp_url = debug://localhost:1025
 
+available_locales = en de
 enable_account_registration = true
 
 session_key = hklurha7ildshgfljhrbuajelghug
diff --git a/fietsboek/__init__.py b/fietsboek/__init__.py
index 80b6c7d..98e6846 100644
--- a/fietsboek/__init__.py
+++ b/fietsboek/__init__.py
@@ -4,11 +4,39 @@ For more information, see the README or the included documentation.
 """
 from pyramid.config import Configurator
 from pyramid.session import SignedCookieSessionFactory
-from pyramid.settings import asbool
+from pyramid.settings import asbool, aslist
+from pyramid.i18n import default_locale_negotiator
 
 from .security import SecurityPolicy
 
 
+def locale_negotiator(request):
+    """Negotiates the right locale to use.
+
+    This tries the following:
+    1. It runs the default negotiator. This allows the locale to be overriden
+       by using the _LOCALE_ query parameter.
+    2. It uses the `Accept-Language`_ header.
+
+    .. Accept-Language: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept-Language
+
+    :param request: The request for which to get the language.
+    :type request: pyramid.request.Request
+    :return: The determined locale, or ``None`` if the default should be used.
+    :rtype: str
+    """
+    locale = default_locale_negotiator(request)
+    if locale:
+        return locale
+
+    installed_locales = request.registry.settings['available_locales']
+    sentinel = object()
+    negotiated = request.accept_language.lookup(installed_locales, default=sentinel)
+    if negotiated is sentinel:
+        return None
+    return negotiated
+
+
 def main(global_config, **settings):
     """ This function returns a Pyramid WSGI application.
     """
@@ -18,6 +46,8 @@ def main(global_config, **settings):
 
     settings['enable_account_registration'] = asbool(
         settings.get('enable_account_registration', 'false'))
+    settings['available_locales'] = aslist(
+        settings.get('available_locales', 'en'))
 
     my_session_factory = SignedCookieSessionFactory(settings['session_key'])
     with Configurator(settings=settings) as config:
@@ -28,4 +58,5 @@ def main(global_config, **settings):
         config.add_translation_dirs('fietsboek:locale/')
         config.set_session_factory(my_session_factory)
         config.set_security_policy(SecurityPolicy())
+        config.set_locale_negotiator(locale_negotiator)
     return config.make_wsgi_app()