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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 hasattr(regex_pattern, "_get_callback"):  # Django==1.2
        if not regex_pattern._callback:
            # enforce _callback resolving
            regex_pattern._get_callback()

        regex_pattern._callback = \
            csrf.csrf_exempt(regex_pattern._callback)
    else:
        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'):  # Django ==1.2
        entries = r._get_url_patterns()
    elif hasattr(r, 'url_patterns'):
        entries = r.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