View dispatch based on HTTP verb

"""
Helper utility for passing control to different views based on the HTTP method.

Construct instances of this class with a dictionary mapping method names (or
sequence of method names) to the view function that will handle them. The
special and optional '__default__' key is used to handle all otherwise
unmentioned methods. Methods not mentioned in the dictionary are implicitly
forbidden if there is no '__default__' key.

For example:

    dispatch_dict = {
        ('POST', 'PUT') : new_data_handler,
        'GET': display_only_handler
    }

    urlconf = patterns('',
        url('/my/pattern/', MethodDispatcher(dispatch_dict))
    )

Each view function in the dictionary will be passed the same set of arguments,
so be prepared to use *args and/or **kwargs if you need to make the function
signatures uniform.
"""
from django import http

class MethodDispatcher(object):
    def __init__(self, method_map):
        self.methods = {}
        self.default = None
        for key, value in method_map.items():
            if key == '__default__':
                self.default = value
            elif isinstance(key, basestring):
                self.methods[key] = value
            else:
                for elt in key:
                    self.methods[elt] = value

    def __call__(self, request, *args, **kwargs):
        view_func = self.methods.get(request.method, self.default)
        if view_func:
            return view_func(request, *args, **kwargs)
        return http.HttpResponseNotAllowed(self.methods.keys())