# -*- coding: utf-8 -*-
from plone.browserlayer.interfaces import ILocalBrowserLayerType
from zope.component import getAllUtilitiesRegisteredFor
from zope.interface import directlyProvidedBy
from zope.interface import directlyProvides
from zope.interface import Interface


def mark_layer(site, event):
    """Mark the request with all installed layers.
    """
    if getattr(event.request, "_plonebrowserlayer_", False):
        return
    event.request._plonebrowserlayer_ = True

    request = event.request
    layers = getAllUtilitiesRegisteredFor(ILocalBrowserLayerType)
    # Filter out bad entries, for example stale utility registrations
    # from removed packages.
    layers = [layer for layer in layers if issubclass(layer, Interface)]
    ifaces = list(layers) + list(directlyProvidedBy(request))

    # Since we allow multiple markers here, we can't use
    # zope.publisher.browser.applySkin() since this filters out
    # IBrowserSkinType interfaces, nor can we use alsoProvides(), since
    # this appends the interface (in which case we end up *after* the
    # default Plone/CMF skin)

    directlyProvides(request, *ifaces)