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"""

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    WSGI application implementation

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"""

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# for error reporting

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import sys, traceback

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# for Request/Response

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import http

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class Application (object) :

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    """

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        Our WSGI application, implements the wsgi __call__ interface

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    """

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    def __init__ (self, handler) :

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        """

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            Initialize to use the given handler for requests

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        """

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        self.handler = handler

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    def handle_request (self, env, start_response) :

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        """

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            The actual request handling code

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        """

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        # build Request object

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        request = http.Request(env)

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        try :

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            # request -> response using our handler

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            response = self.handler.handle_request(request)

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        except http.ResponseError, err :

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            # just use the generated response

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            response = err.get_response()

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        # send response

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        assert response, "No response"

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        # send response status/headers

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        start_response(response.get_status(), response.get_headers())

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        # send respones data

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        yield response.get_data()

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    def handle_error (self, exc_info, env, start_response) :

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        """

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            Handle errors thrown by handle_request. This should call start_response with the exc_info and return the

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            error message (i.e. str), otherwise the error will be thrown up yet another level.

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            Note that e.g. unicode is a failure...

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        """

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        # try and send 500 ISE to browser, if no headers yet...

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        start_response("500 Internal Server Error", [('Content-type', "text/plain; charset=UTF-8")], exc_info)

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        # format traceback

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        data = ''.join(traceback.format_exception(*exc_info))

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        # no unicode, kplzthx

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        return data.encode('utf-8')

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    def __call__ (self, env, start_response) :

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        """

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            Wraps handle_request to trap errors

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        """

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        try :

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            # passthrough request_handler

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            for chunk in self.handle_request(env, start_response) :

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                yield chunk

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        except :

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            # execption info

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            info = sys.exc_info()

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            # handle

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            yield self.handle_error(info, env, start_response)

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