""" The default base class for extension providers. """


# Enthought library imports.
from traits.api import Event, HasTraits, implements

# Local imports.
from extension_point_changed_event import ExtensionPointChangedEvent
from i_extension_provider import IExtensionProvider


class ExtensionProvider(HasTraits):
    """ The default base class for extension providers. """

    implements(IExtensionProvider)

    #### 'IExtensionProvider' interface #######################################

    # The event fired when one of the provider's extension points has been
    # changed (where 'changed' means that the provider has added or removed
    # contributions to or from an extension point).
    extension_point_changed = Event(ExtensionPointChangedEvent)

    def get_extension_points(self):
        """ Return the extension points offered by the provider. """

        return []

    def get_extensions(self, extension_point_id):
        """ Return the provider's extensions to an extension point. """

        return []

    ##### Protected 'ExtensionProvider' interface #############################

    def _fire_extension_point_changed(
        self, extension_point_id, added, removed, index
    ):
        """ Fire an extension point changed event. """

        self.extension_point_changed = ExtensionPointChangedEvent(
            extension_point_id = extension_point_id,
            added              = added,
            removed            = removed,
            index              = index
        )

        return

#### EOF ######################################################################
