--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/app/soc/modules/core.py	Sun May 24 21:40:37 2009 +0200
@@ -0,0 +1,235 @@
+# Copyright 2009 the Melange authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""The Melange Core module.
+"""
+
+__authors__ = [
+  '"Sverre Rabbelier" <sverre@rabbelier.nl>',
+  '"Lennard de Rijk" <ljvderijk@gmail.com>',
+  ]
+
+
+from django.conf.urls import defaults
+
+import settings
+import soc.cache.sidebar
+
+
+class Error(Exception):
+  """Error class for the callback module.
+  """
+
+  pass
+
+
+class APIVersionMismatch(Error):
+  """Error raised when API version mismatches.
+  """
+
+  MISMATCH_MSG_FMT = "API mismatch, expected '%d', got '%d'."
+
+  def __init__(self, expected, actual):
+    """Instantiates a new exception with a customized message.
+    """
+
+    msg = self.MISMATCH_MSG_FMT % (expected, actual)
+    super(APIVersionMismatch, self).__init__(msg)
+
+
+class MissingService(Error):
+  """Error raised when a required service is missing.
+  """
+
+  MISSING_SERVICE_FMT = "Required service '%s' is not registered, known: %s"
+
+  def __init__(self, service, services):
+    """Instantiates a new exception with a customized message.
+    """
+
+    msg = self.MISSING_SERVICE_FMT % (service, services)
+    super(MissingService, self).__init__(msg)
+
+
+class NonUniqueService(Error):
+  """Error raised when a required service is missing.
+  """
+
+  NON_UNIQUE_SERVICE_FMT = "Unique service '%s' called a second time, known: %s."
+
+  def __init__(self, service, services):
+    """Instantiates a new exception with a customized message.
+    """
+
+    msg = self.NON_UNIQUE_SERVICE_FMT % (service, services)
+    super(NonUniqueService, self).__init__(msg)
+
+
+class Core(object):
+  """The core handler that controls the Melange API.
+  """
+
+  def __init__(self):
+    """Creates a new instance of the Core.
+    """
+
+    self.API_VERSION = 1
+
+    self.registered_callbacks = []
+    self.capability = []
+    self.services = []
+
+    self.sitemap = []
+    self.sidebar = []
+
+  ##
+  ## internal
+  ##
+
+  def getService(self, callback, service):
+   """Retrieves the specified service from the callback if supported.
+
+   Args:
+     callback: the callback to retrieve the capability from
+     service: the service to retrieve
+   """
+
+   if not hasattr(callback, service):
+     return False
+
+   func = getattr(callback, service)
+
+   if not callable(func):
+     return False
+
+   return func
+
+  ##
+  ## Core code
+  ##
+
+  def getPatterns(self):
+    """Returns the Django patterns for this site.
+    """
+
+    self.callService('registerWithSitemap', True)
+    return defaults.patterns(None, *self.sitemap)
+
+  @soc.cache.sidebar.cache
+  def getSidebar(self, id, user):
+    """Constructs a sidebar for the current user.
+    """
+
+    self.callService('registerWithSidebar', True)
+
+    sidebar = []
+
+    for i in self.sidebar:
+      menus = i(id, user)
+
+      for menu in (menus if menus else []):
+        sidebar.append(menu)
+
+    return sorted(sidebar, key=lambda x: x.get('group'))
+
+  def callService(self, service, unique, *args, **kwargs):
+    """Calls the specified service on all callbacks.
+    """
+
+    if unique and (service in self.services):
+      return
+
+    results = []
+
+    for callback in self.registered_callbacks:
+      func = self.getService(callback, service)
+      if not func:
+        continue
+
+      result = func(*args, **kwargs)
+      results.append(result)
+
+    self.services.append(service)
+    return results
+
+  def registerModuleCallbacks(self):
+    """Retrieves all callbacks for the modules of this site.
+
+    Callbacks for modules without a version number or the wrong API_VERSION
+    number are dropped.  They won't be called.
+    """
+
+    fmt = settings.MODULE_FMT
+    modules = ['soc_core'] + settings.MODULES
+    modules = [__import__(fmt % i, fromlist=['']) for i in modules]
+
+    for callback_class in [i.getCallback() for i in modules]:
+      if callback_class.API_VERSION != self.API_VERSION:
+        raise callback.APIVersionMismatch(self.API_VERSION,
+                                          callback_class.API_VERSION)
+
+
+      callback = callback_class(self)
+      self.registered_callbacks.append(callback)
+
+    return True
+
+  ##
+  ## Module code
+  ##
+
+  def registerCapability(self, capability):
+    """Registers the specified capability.
+    """
+
+    self.capabilities.append(capability)
+
+  def requireCapability(self, capability):
+    """Requires that the specified capability is present.
+    """
+
+    if capability in self.capabilities:
+      return True
+
+    raise MissingCapability(capability, self.capability)
+
+  def requireService(self, service):
+    """Requires that the specified service has been called.
+    """
+
+    if service in self.services:
+      return True
+
+    raise MissingService(service, self.services)
+
+  def requireUniqueService(self, service):
+    """Requires that the specified service is called exactly once.
+    """
+
+    if service not in self.services:
+      return True
+
+    raise NonUniqueService(service, self.services)
+
+  def registerSitemapEntry(self, entries):
+    """Registers the specified entries with the sitemap.
+    """
+
+    self.sitemap.extend(entries)
+
+  def registerSidebarEntry(self, entry):
+    """Registers the specified entry with the sidebar.
+    """
+
+    self.sidebar.append(entry)