import re
from haystack.constants import ID, DJANGO_CT, DJANGO_ID
from haystack.utils.highlighting import Highlighter


IDENTIFIER_REGEX = re.compile('^[\w\d_]+\.[\w\d_]+\.\d+$')


def get_model_ct(model):
    return "%s.%s" % (model._meta.app_label, model._meta.module_name)


def get_identifier(obj_or_string):
    """
    Get an unique identifier for the object or a string representing the
    object.
    
    If not overridden, uses <app_label>.<object_name>.<pk>.
    """
    if isinstance(obj_or_string, basestring):
        if not IDENTIFIER_REGEX.match(obj_or_string):
            raise AttributeError("Provided string '%s' is not a valid identifier." % obj_or_string)
        
        return obj_or_string
    
    return u"%s.%s.%s" % (obj_or_string._meta.app_label, obj_or_string._meta.module_name, obj_or_string._get_pk_val())


def get_facet_field_name(fieldname):
    if fieldname in [ID, DJANGO_ID, DJANGO_CT]:
        return fieldname
    
    return "%s_exact" % fieldname