Decorate every view in a url tree

'''
Author: Stephen J. Zabel
License: BSD

This module exposed a helper function for
wrapping views at the urls.py/resolver level

My personal little itch as an example...

urlpatterns += required(
    login_required,
    patterns('',
        (r'^api/', 
            include(api.urls)),
    )
)
'''


def required(wrapping_functions,patterns_rslt):
    '''
    Used to require 1..n decorators in any view returned by a url tree

    Usage:
      urlpatterns = required(func,patterns(...))
      urlpatterns = required((func,func,func),patterns(...))

    Note:
      Use functools.partial to pass keyword params to the required 
      decorators. If you need to pass args you will have to write a 
      wrapper function.

    Example:
      from functools import partial

      urlpatterns = required(
          partial(login_required,login_url='/accounts/login/'),
          patterns(...)
      )
    '''
    if not hasattr(wrapping_functions,'__iter__'): 
        wrapping_functions = (wrapping_functions,)

    return [
        _wrap_instance__resolve(wrapping_functions,instance)
        for instance in patterns_rslt
    ]

def _wrap_instance__resolve(wrapping_functions,instance):
    if not hasattr(instance,'resolve'): return instance
    resolve = getattr(instance,'resolve')

    def _wrap_func_in_returned_resolver_match(*args,**kwargs):
        rslt = resolve(*args,**kwargs)

        if not hasattr(rslt,'func'):return rslt
        f = getattr(rslt,'func')

        for _f in reversed(wrapping_functions):
            # @decorate the function from inner to outter
            f = _f(f)

        setattr(rslt,'func',f)

        return rslt

    setattr(instance,'resolve',_wrap_func_in_returned_resolver_match)

    return instance