from AccessControl import getSecurityManager
from AccessControl import Unauthorized
from Products.PageTemplates.PageTemplateFile import PageTemplateFile as Z2PTF
from zope.pagetemplate.pagetemplatefile import PageTemplateFile as Z3PTF
from Products.Five.browser.pagetemplatefile import BoundPageTemplate as Z2BPT
 
 
def isTemplate(obj):
    """ check if the given object is a or is derived from a template class """
    # TODO: we should really check via interfaces, i.e. `providedBy` here,
    #       but the only class using interfaces atm is Z3PTF :(
    return isinstance(obj, (Z2PTF, Z3PTF, Z2BPT))
 
 
def findViewletTemplate(viewlet):
    """ try to find the attribute holding the template within a viewlet """
    for attr in 'index', 'template', '_template', '__call__', 'render':
        item = getattr(viewlet, attr, None)
        if isTemplate(item):
            return attr, item
    attrs = [ attr for attr in dir(viewlet) if isTemplate(getattr(viewlet, attr, None)) ]
    if len(attrs) == 1:
        return attrs[0], getattr(viewlet, attrs[0])
    else:
        # TODO: we should pass on the message if we find multiple templates
        pass
    return None, None
 
 
def checkPermission(permission, context):
    sm = getSecurityManager()
    if permission is not None:
        if not sm.checkPermission(permission, context):
            raise Unauthorized('The current user does not have the '
                               'required "%s" permission' % permission)