"""

Contains some data structures.

"""

from webob.util.dictmixin import DictMixin

class EnvironHeaders(DictMixin):

    """An object that represents the headers as present in a

    WSGI environment.

    This object is a wrapper (with no internal state) for a WSGI

    request object, representing the CGI-style HTTP_* keys as a

    dictionary.  Because a CGI environment can only hold one value for

    each key, this dictionary is single-valued (unlike outgoing

    headers).

    """

    def __init__(self, environ):

        self.environ = environ

    def _trans_name(self, name):

        key = 'HTTP_'+name.replace('-', '_').upper()

        if key == 'HTTP_CONTENT_LENGTH':

            key = 'CONTENT_LENGTH'

        elif key == 'HTTP_CONTENT_TYPE':

            key = 'CONTENT_TYPE'

        return key

    def _trans_key(self, key):

        if key == 'CONTENT_TYPE':

            return 'Content-Type'

        elif key == 'CONTENT_LENGTH':

            return 'Content-Length'

        elif key.startswith('HTTP_'):

            return key[5:].replace('_', '-').title()

        else:

            return None

    def __getitem__(self, item):

        return self.environ[self._trans_name(item)]

    def __setitem__(self, item, value):

        self.environ[self._trans_name(item)] = value

    def __delitem__(self, item):

        del self.environ[self._trans_name(item)]

    def __iter__(self):

        for key in self.environ:

            name = self._trans_key(key)

            if name is not None:

                yield name

    def keys(self):

        return list(iter(self))

    def __contains__(self, item):

        return self._trans_name(item) in self.environ