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from django.core import urlresolvers
from django.views.decorators import csrf
from django.conf.urls.defaults import patterns

def _patch_pattern(regex_pattern):
    """
    Patch pattern callback using csrf_exempt. Enforce 
    RegexURLPattern callback to get resolved if required.
    """
    if not regex_pattern._callback:
        # enforce _callback resolving
        regex_pattern._get_callback()

    regex_pattern._callback = \
            csrf.csrf_exempt(regex_pattern._callback)

def _patch_resolver(r):
    """
    Patch all patterns found in resolver with _patch_pattern
    """
    if hasattr(r, '_get_url_patterns'):
        entries = r._get_url_patterns()
    else:
        # first level view in patterns ?
        entries = [r]

    for entry in entries:
        if isinstance(entry, urlresolvers.RegexURLResolver):
            _patch_resolver(entry)
        #if isinstance(entry, urlresolvers.RegexURLPattern):
        # let it break...
        else:
            _patch_pattern(entry)

def api_patterns(*args, **kwargs):
    """
    Protect all url patterns from csrf attacks. 
    """
    _patterns = patterns(*args, **kwargs)
    for entry in _patterns:
        _patch_resolver(entry)
    return _patterns