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"""

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    WSGI HTTP utility code

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"""

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# for utility functions

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import cgi

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# for header handling

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import wsgiref.headers

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# for path handling

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import os.path

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class Request (object) :

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    """

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        HTTP Request with associated metadata

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    """

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    def __init__ (self, env) :

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        """

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            Parse env data

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        """

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        # store env

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        self.env = env

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        # get the querystring

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        self.arg_str = env.get('QUERY_STRING', '')

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        # parse query args

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        self.arg_dict = cgi.parse_qs(self.arg_str, True)

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    @property

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    def site_host (self) :

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        """

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            Returns the site's hostname (DNS name)

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        """

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        return self.env['HTTP_HOST']

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    @property

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    def site_root (self) :

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        """

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            Returns the URL path to the requested script's directory with no trailing slash, i.e.

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            /               -> 

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            /foo.cgi        -> 

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            /foo/bar.cgi    -> /foo

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        """

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        return os.path.dirname(self.env['SCRIPT_NAME']).rstrip('/')

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    @property

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    def page_prefix (self) :

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        """

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            Returns the URL path root for page URLs, based on REQUEST_URI with PATH_INFO removed

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            /                   -> 

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            /foo.cgi            -> /foo.cgi

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            /foo.cgi/index      -> /foo.cgi

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            /foo.cgi/quux/bar   -> /foo.cgi

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            /quux/foo.cgi/bar   -> /quux/foo.cgi

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            /bar                -> 

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        """

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        # XXX: request uri path without the query string

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        request_path = self.env.get('REQUEST_URI', '').split('?', 1)[0].rstrip('/')

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        # path info

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        page_name = self.get_page_name()

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        # special-case for empty page_name

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        if not page_name :

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            return request_path

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        # sanity-check

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        assert request_path.endswith(page_name)

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        # trim

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        return request_path[:-len(page_name)].rstrip('/')

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    def get_page_name (self) :

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        """

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            Returns the requested page path with no leading slash, i.e.

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            /foo.cgi        -> 

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            /foo.cgi/       -> 

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            /foo.cgi/bar    -> bar

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            /foo.cgi/quux/  -> quux/

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        """

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        # the raw PATH_INFO

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        path_info = self.env.get('PATH_INFO')

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        # avoid nasty '.' paths

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        if path_info :

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            return os.path.normpath(path_info).lstrip('/')

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        else :

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            return ''

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    def get_arg (self, name, default=None) :

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        """

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            Get a single value for an argument with the given key, or the default if missing

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        """

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        if name in self.arg_dict :

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            return self.arg_dict[name][0]

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        else :

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            return default

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    def get_args (self) :

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        """

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            Iterate over all available (key, value) pairs from the query string

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        """

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        return cgi.parse_qsl(self.arg_str)

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class Response (object) :

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    """

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        HTTP Response with headers and data

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    """

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    def __init__ (self, data, content_type='text/html', status='200 OK', charset='UTF-8') :

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        """

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            Create the response. The Content-type header is built from the given values. The given \a data must be

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            either a str (which is sent plain), an unicode object (which is encoded with the relevant charset), or

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            None, whereupon an empty response body is sent. The content_type argument can also be forced to None to

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            not send a Content-type header (e.g. for redirects)

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        """

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        # store info

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        self.status = status

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        self.data = data

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        self.charset = charset

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        # headers

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        self.headers = wsgiref.headers.Headers([])

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        # add Content-type header?

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        if content_type :

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            self.add_header('Content-type', content_type, charset=charset)

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    def add_header (self, name, value, **params) :

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        """

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            Add response header with the given name/value, plus option params

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            XXX: uses the wsgiref.headers code, not sure how that behaves re multiple headers with the same name, etc

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        """

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        self.headers.add_header(name, value, **params)

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    def get_status (self) :

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        """

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            Returns response status string (XXX Foo)

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        """

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        return self.status

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    def get_headers (self) :

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        """

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            Returns the list of header (name, value) pairs

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        """

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        return self.headers.items()

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    def get_data (self) :

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        """

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            Returns the response data - as an encoded string

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        """

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        if self.data :

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            return self.data.encode(self.charset)

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        else :

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            return ''

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class ErrorResponse (Response) :

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    """

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        A response with an error code / message

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    """

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    def __init__ (self, status, message, details=None) :

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        """

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            Build a plain error message response with the given status/message

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            @param status HTTP status code

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            @param message short message to describe errors

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            @param details optional details, plaintext

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        """

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        data = """\

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<html><head><title>%(title)s</title></head><body>

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<h1>%(title)s</h1>

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<p>%(message)s</p>

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%(details)s

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</body></html>

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""" % dict(

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            title       = status, 

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            message     = message,

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            details     = '<pre>%s</pre>' % details if details else ''

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        )

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        super(ErrorResponse, self).__init__(data, status=status)

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class ResponseError (Exception) :

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    """

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        An exception that results in a specfic 4xx ErrorResponse message to the client

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    """

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    def __init__ (self, message, status='400 Bad Request', details=None) :

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        self.status = status

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        self.message = message

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        self.details = details

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        super(ResponseError, self).__init__(message)

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    def get_response (self) :

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        return ErrorResponse(self.status, self.message, self.details)

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class Redirect (Response) :

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    """

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        Redirect response

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    """

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    def __init__ (self, url) :

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        """

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            Redirect to given *absolute* URL

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        """

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        # no content-type or data

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        super(Redirect, self).__init__(None, content_type=None, status='302 Found')

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        # add Location: header

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        self.add_header("Location", url)

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