Unifies Horizon conf.

Centralizes all of Horizon's configuration options so that
they're all uniformly accesible from a single place and always
guaranteed to exist.

Implements blueprint unify-config.

Change-Id: I3279b7ccd58302fcff4f0d273f89f282a285c442

horizon/conf/__init__.py

@@ -0,0 +1,35 @@
+import copy
+
+from django.utils.functional import LazyObject, empty
+
+from .default import HORIZON_CONFIG as DEFAULT_CONFIG
+
+
+class LazySettings(LazyObject):
+    def _setup(self, name=None):
+        from django.conf import settings
+        HORIZON_CONFIG = copy.copy(DEFAULT_CONFIG)
+        HORIZON_CONFIG.update(settings.HORIZON_CONFIG)
+
+        # Ensure we always have our exception configuration...
+        for exc_category in ['unauthorized', 'not_found', 'recoverable']:
+            if exc_category not in HORIZON_CONFIG['exceptions']:
+                default_exc_config = DEFAULT_CONFIG['exceptions'][exc_category]
+                HORIZON_CONFIG['exceptions'][exc_category] = default_exc_config
+
+        # Ensure our password validator always exists...
+        if 'regex' not in HORIZON_CONFIG['password_validator']:
+            default_pw_regex = DEFAULT_CONFIG['password_validator']['regex']
+            HORIZON_CONFIG['password_validator']['regex'] = default_pw_regex
+        if 'help_text' not in HORIZON_CONFIG['password_validator']:
+            default_pw_help = DEFAULT_CONFIG['password_validator']['help_text']
+            HORIZON_CONFIG['password_validator']['help_text'] = default_pw_help
+
+        self._wrapped = HORIZON_CONFIG
+
+    def __getitem__(self, name, fallback=None):
+        if self._wrapped is empty:
+            self._setup(name)
+        return self._wrapped.get(name, fallback)
+
+HORIZON_CONFIG = LazySettings()

horizon/conf/default.py

@@ -0,0 +1,30 @@
+from django.conf import settings
+from django.utils.translation import ugettext as _
+
+# Default configuration dictionary. Do not mutate.
+HORIZON_CONFIG = {
+    # Allow for ordering dashboards; list or tuple if provided.
+    'dashboards': None,
+
+    # Name of a default dashboard; defaults to first alphabetically if None
+    'default_dashboard': None,
+
+    # Default redirect url for users' home
+    'user_home': settings.LOGIN_REDIRECT_URL,
+
+    # AJAX settings for JavaScript
+    'ajax_queue_limit': 10,
+    'ajax_poll_interval': 2500,
+
+    # URL for additional help with this site.
+    'help_url': None,
+
+    # Exception configuration.
+    'exceptions': {'unauthorized': [],
+                   'not_found': [],
+                   'recoverable': []},
+
+    # Password configuration.
+    'password_validator': {'regex': '.*',
+                           'help_text': _("Password is not accepted")}
+}