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# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# Copyright 2010 OpenStack LLC.
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

"""Utility methods for working with WSGI servers."""

import logging
import os
import sys

import eventlet
import eventlet.wsgi
eventlet.patcher.monkey_patch(all=False, socket=True, time=True)
import routes
import routes.middleware
import webob
import webob.dec
import webob.exc
from paste import deploy


class WritableLogger(object):
    """A thin wrapper that responds to `write` and logs."""

    def __init__(self, logger, level=logging.DEBUG):
        self.logger = logger
        self.level = level

    def write(self, msg):
        self.logger.log(self.level, msg)


class Server(object):
    """Server class to manage multiple WSGI sockets and applications."""

    def __init__(self, threads=1000):
        self.pool = eventlet.GreenPool(threads)
        self.socket_info = {}

    def start(self, application, port, host='0.0.0.0', key=None, backlog=128):
        """Run a WSGI server with the given application."""
        self.application = application
        arg0 = sys.argv[0]
        logging.debug('Starting %(arg0)s on %(host)s:%(port)s' % locals())
        socket = eventlet.listen((host, port), backlog=backlog)
        self.pool.spawn_n(self._run, application, socket)
        if key:
            self.socket_info[key] = socket.getsockname()

    def wait(self):
        """Wait until all servers have completed running."""
        try:
            self.pool.waitall()
        except KeyboardInterrupt:
            pass

    def _run(self, application, socket):
        """Start a WSGI server in a new green thread."""
        logger = logging.getLogger('eventlet.wsgi.server')
        eventlet.wsgi.server(socket, application, custom_pool=self.pool,
                             log=WritableLogger(logger))


class Request(webob.Request):
    pass


class Application(object):
    """Base WSGI application wrapper. Subclasses need to implement __call__."""

    @classmethod
    def factory(cls, global_config, **local_config):
        """Used for paste app factories in paste.deploy config files.

        Any local configuration (that is, values under the [app:APPNAME]
        section of the paste config) will be passed into the `__init__` method
        as kwargs.

        A hypothetical configuration would look like:

            [app:wadl]
            latest_version = 1.3
            paste.app_factory = nova.api.fancy_api:Wadl.factory

        which would result in a call to the `Wadl` class as

            import nova.api.fancy_api
            fancy_api.Wadl(latest_version='1.3')

        You could of course re-implement the `factory` method in subclasses,
        but using the kwarg passing it shouldn't be necessary.

        """
        return cls(**local_config)

    def __call__(self, environ, start_response):
        r"""Subclasses will probably want to implement __call__ like this:

        @webob.dec.wsgify(RequestClass=Request)
        def __call__(self, req):
          # Any of the following objects work as responses:

          # Option 1: simple string
          res = 'message\n'

          # Option 2: a nicely formatted HTTP exception page
          res = exc.HTTPForbidden(detail='Nice try')

          # Option 3: a webob Response object (in case you need to play with
          # headers, or you want to be treated like an iterable, or or or)
          res = Response();
          res.app_iter = open('somefile')

          # Option 4: any wsgi app to be run next
          res = self.application

          # Option 5: you can get a Response object for a wsgi app, too, to
          # play with headers etc
          res = req.get_response(self.application)

          # You can then just return your response...
          return res
          # ... or set req.response and return None.
          req.response = res

        See the end of http://pythonpaste.org/webob/modules/dec.html
        for more info.

        """
        raise NotImplementedError('You must implement __call__')


class Middleware(Application):
    """Base WSGI middleware.

    These classes require an application to be
    initialized that will be called next.  By default the middleware will
    simply call its wrapped app, or you can override __call__ to customize its
    behavior.

    """

    @classmethod
    def factory(cls, global_config, **local_config):
        """Used for paste app factories in paste.deploy config files.

        Any local configuration (that is, values under the [filter:APPNAME]
        section of the paste config) will be passed into the `__init__` method
        as kwargs.

        A hypothetical configuration would look like:

            [filter:analytics]
            redis_host = 127.0.0.1
            paste.filter_factory = nova.api.analytics:Analytics.factory

        which would result in a call to the `Analytics` class as

            import nova.api.analytics
            analytics.Analytics(app_from_paste, redis_host='127.0.0.1')

        You could of course re-implement the `factory` method in subclasses,
        but using the kwarg passing it shouldn't be necessary.

        """
        def _factory(app):
            conf = global_config.copy()
            conf.update(local_config)
            return cls(app, conf)
        return _factory

    def __init__(self, application, options):
        self.application = application
        self.options = options

    def process_request(self, req):
        """Called on each request.

        If this returns None, the next application down the stack will be
        executed. If it returns a response then that response will be returned
        and execution will stop here.

        """
        return None

    def process_response(self, response):
        """Do whatever you'd like to the response."""
        return response

    @webob.dec.wsgify(RequestClass=Request)
    def __call__(self, req):
        response = self.process_request(req)
        if response:
            return response
        response = req.get_response(self.application)
        return self.process_response(response)


class Debug(Middleware):
    """Helper class for debugging a WSGI application.

    Can be inserted into any WSGI application chain to get information
    about the request and response.

    """

    @webob.dec.wsgify(RequestClass=Request)
    def __call__(self, req):
        logging.debug('%s %s %s', ('*' * 20), 'REQUEST ENVIRON', ('*' * 20))
        for key, value in req.environ.items():
            logging.debug('%s = %s', key, value)
        logging.debug('')
        logging.debug('%s %s %s', ('*' * 20), 'REQUEST BODY', ('*' * 20))
        for line in req.body_file:
            logging.debug(line)
        logging.debug('')


        resp = req.get_response(self.application)

        logging.debug('%s %s %s', ('*' * 20), 'RESPONSE HEADERS', ('*' * 20))
        for (key, value) in resp.headers.iteritems():
            logging.debug('%s = %s', key, value)
        logging.debug('')

        resp.app_iter = self.print_generator(resp.app_iter)

        return resp

    @staticmethod
    def print_generator(app_iter):
        """Iterator that prints the contents of a wrapper string."""
        logging.debug('%s %s %s', ('*' * 20), 'RESPONSE BODY', ('*' * 20))
        for part in app_iter:
            sys.stdout.write(part)
            #sys.stdout.flush()
            yield part
        print


class Router(object):
    """WSGI middleware that maps incoming requests to WSGI apps."""

    def __init__(self, mapper):
        """Create a router for the given routes.Mapper.

        Each route in `mapper` must specify a 'controller', which is a
        WSGI app to call.  You'll probably want to specify an 'action' as
        well and have your controller be an object that can route
        the request to the action-specific method.

        Examples:
          mapper = routes.Mapper()
          sc = ServerController()

          # Explicit mapping of one route to a controller+action
          mapper.connect(None, '/svrlist', controller=sc, action='list')

          # Actions are all implicitly defined
          mapper.resource('server', 'servers', controller=sc)

          # Pointing to an arbitrary WSGI app.  You can specify the
          # {path_info:.*} parameter so the target app can be handed just that
          # section of the URL.
          mapper.connect(None, '/v1.0/{path_info:.*}', controller=BlogApp())

        """
        self.map = mapper
        self._router = routes.middleware.RoutesMiddleware(self._dispatch,
                                                          self.map)

    @webob.dec.wsgify(RequestClass=Request)
    def __call__(self, req):
        """Route the incoming request to a controller based on self.map.

        If no match, return a 404.

        """
        return self._router

    @staticmethod
    @webob.dec.wsgify(RequestClass=Request)
    def _dispatch(req):
        """Dispatch the request to the appropriate controller.

        Called by self._router after matching the incoming request to a route
        and putting the information into req.environ.  Either returns 404
        or the routed WSGI app's response.

        """
        match = req.environ['wsgiorg.routing_args'][1]
        if not match:
            return webob.exc.HTTPNotFound()
        app = match['controller']
        return app


def paste_config_file(basename):
    """Find the best location in the system for a paste config file.

    Search Order
    ------------

    The search for a paste config file honors `FLAGS.state_path`, which in a
    version checked out from bzr will be the `nova` directory in the top level
    of the checkout, and in an installation for a package for your distribution
    will likely point to someplace like /etc/nova.

    This method tries to load places likely to be used in development or
    experimentation before falling back to the system-wide configuration
    in `/etc/nova/`.

    * Current working directory
    * the `etc` directory under state_path, because when working on a checkout
      from bzr this will point to the default
    * top level of FLAGS.state_path, for distributions
    * /etc/nova, which may not be diffrerent from state_path on your distro

    """
    configfiles = [basename,
                   os.path.join(FLAGS.state_path, 'etc', 'nova', basename),
                   os.path.join(FLAGS.state_path, 'etc', basename),
                   os.path.join(FLAGS.state_path, basename),
                   '/etc/nova/%s' % basename]
    for configfile in configfiles:
        if os.path.exists(configfile):
            return configfile


def load_paste_configuration(filename, appname):
    """Returns a paste configuration dict, or None."""
    filename = os.path.abspath(filename)
    config = None
    try:
        config = deploy.appconfig('config:%s' % filename, name=appname)
    except LookupError:
        pass
    return config


def load_paste_app(filename, appname):
    """Builds a wsgi app from a paste config, None if app not configured."""
    filename = os.path.abspath(filename)
    app = None
    try:
        app = deploy.loadapp('config:%s' % filename, name=appname)
    except LookupError:
        pass
    return app