# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# Copyright 2010 OpenStack Foundation
# 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."""

from __future__ import print_function

import os.path
import socket
import ssl
import sys

import eventlet
import eventlet.wsgi
import greenlet
from oslo.config import cfg
from oslo.utils import excutils
from paste import deploy
import routes.middleware
import webob.dec
import webob.exc

from nova import exception
from nova.i18n import _, _LE
from nova.openstack.common import log as logging

wsgi_opts = [
    cfg.StrOpt('api_paste_config',
               default="api-paste.ini",
               help='File name for the paste.deploy config for nova-api'),
    cfg.StrOpt('wsgi_log_format',
            default='%(client_ip)s "%(request_line)s" status: %(status_code)s'
                    ' len: %(body_length)s time: %(wall_seconds).7f',
            help='A python format string that is used as the template to '
                 'generate log lines. The following values can be formatted '
                 'into it: client_ip, date_time, request_line, status_code, '
                 'body_length, wall_seconds.'),
    cfg.StrOpt('ssl_ca_file',
               help="CA certificate file to use to verify "
                    "connecting clients"),
    cfg.StrOpt('ssl_cert_file',
                    help="SSL certificate of API server"),
    cfg.StrOpt('ssl_key_file',
                    help="SSL private key of API server"),
    cfg.IntOpt('tcp_keepidle',
               default=600,
               help="Sets the value of TCP_KEEPIDLE in seconds for each "
                    "server socket. Not supported on OS X."),
    cfg.IntOpt('wsgi_default_pool_size',
               default=1000,
               help="Size of the pool of greenthreads used by wsgi"),
    cfg.IntOpt('max_header_line',
               default=16384,
               help="Maximum line size of message headers to be accepted. "
                    "max_header_line may need to be increased when using "
                    "large tokens (typically those generated by the "
                    "Keystone v3 API with big service catalogs)."),
    ]
CONF = cfg.CONF
CONF.register_opts(wsgi_opts)

LOG = logging.getLogger(__name__)


class Server(object):
    """Server class to manage a WSGI server, serving a WSGI application."""

    default_pool_size = CONF.wsgi_default_pool_size

    def __init__(self, name, app, host='0.0.0.0', port=0, pool_size=None,
                       protocol=eventlet.wsgi.HttpProtocol, backlog=128,
                       use_ssl=False, max_url_len=None):
        """Initialize, but do not start, a WSGI server.

        :param name: Pretty name for logging.
        :param app: The WSGI application to serve.
        :param host: IP address to serve the application.
        :param port: Port number to server the application.
        :param pool_size: Maximum number of eventlets to spawn concurrently.
        :param backlog: Maximum number of queued connections.
        :param max_url_len: Maximum length of permitted URLs.
        :returns: None
        :raises: nova.exception.InvalidInput
        """
        # Allow operators to customize http requests max header line size.
        eventlet.wsgi.MAX_HEADER_LINE = CONF.max_header_line
        self.name = name
        self.app = app
        self._server = None
        self._protocol = protocol
        self.pool_size = pool_size or self.default_pool_size
        self._pool = eventlet.GreenPool(self.pool_size)
        self._logger = logging.getLogger("nova.%s.wsgi.server" % self.name)
        self._wsgi_logger = logging.WritableLogger(self._logger)
        self._use_ssl = use_ssl
        self._max_url_len = max_url_len

        if backlog < 1:
            raise exception.InvalidInput(
                    reason='The backlog must be more than 1')

        bind_addr = (host, port)
        # TODO(dims): eventlet's green dns/socket module does not actually
        # support IPv6 in getaddrinfo(). We need to get around this in the
        # future or monitor upstream for a fix
        try:
            info = socket.getaddrinfo(bind_addr[0],
                                      bind_addr[1],
                                      socket.AF_UNSPEC,
                                      socket.SOCK_STREAM)[0]
            family = info[0]
            bind_addr = info[-1]
        except Exception:
            family = socket.AF_INET

        try:
            self._socket = eventlet.listen(bind_addr, family, backlog=backlog)
        except EnvironmentError:
            LOG.error(_LE("Could not bind to %(host)s:%(port)s"),
                      {'host': host, 'port': port})
            raise

        (self.host, self.port) = self._socket.getsockname()[0:2]
        LOG.info(_("%(name)s listening on %(host)s:%(port)s"),
                 {'name': self.name, 'host': self.host, 'port': self.port})

    def start(self):
        """Start serving a WSGI application.

        :returns: None
        """
        # The server socket object will be closed after server exits,
        # but the underlying file descriptor will remain open, and will
        # give bad file descriptor error. So duplicating the socket object,
        # to keep file descriptor usable.

        dup_socket = self._socket.dup()
        if self._use_ssl:
            try:
                ca_file = CONF.ssl_ca_file
                cert_file = CONF.ssl_cert_file
                key_file = CONF.ssl_key_file

                if cert_file and not os.path.exists(cert_file):
                    raise RuntimeError(
                          _("Unable to find cert_file : %s") % cert_file)

                if ca_file and not os.path.exists(ca_file):
                    raise RuntimeError(
                          _("Unable to find ca_file : %s") % ca_file)

                if key_file and not os.path.exists(key_file):
                    raise RuntimeError(
                          _("Unable to find key_file : %s") % key_file)

                if self._use_ssl and (not cert_file or not key_file):
                    raise RuntimeError(
                          _("When running server in SSL mode, you must "
                            "specify both a cert_file and key_file "
                            "option value in your configuration file"))
                ssl_kwargs = {
                    'server_side': True,
                    'certfile': cert_file,
                    'keyfile': key_file,
                    'cert_reqs': ssl.CERT_NONE,
                }

                if CONF.ssl_ca_file:
                    ssl_kwargs['ca_certs'] = ca_file
                    ssl_kwargs['cert_reqs'] = ssl.CERT_REQUIRED

                dup_socket = eventlet.wrap_ssl(dup_socket,
                                               **ssl_kwargs)

                dup_socket.setsockopt(socket.SOL_SOCKET,
                                      socket.SO_REUSEADDR, 1)
                # sockets can hang around forever without keepalive
                dup_socket.setsockopt(socket.SOL_SOCKET,
                                      socket.SO_KEEPALIVE, 1)

                # This option isn't available in the OS X version of eventlet
                if hasattr(socket, 'TCP_KEEPIDLE'):
                    dup_socket.setsockopt(socket.IPPROTO_TCP,
                                    socket.TCP_KEEPIDLE,
                                    CONF.tcp_keepidle)

            except Exception:
                with excutils.save_and_reraise_exception():
                    LOG.error(_LE("Failed to start %(name)s on %(host)s"
                                  ":%(port)s with SSL support"),
                              {'name': self.name, 'host': self.host,
                               'port': self.port})

        wsgi_kwargs = {
            'func': eventlet.wsgi.server,
            'sock': dup_socket,
            'site': self.app,
            'protocol': self._protocol,
            'custom_pool': self._pool,
            'log': self._wsgi_logger,
            'log_format': CONF.wsgi_log_format,
            'debug': False
            }

        if self._max_url_len:
            wsgi_kwargs['url_length_limit'] = self._max_url_len

        self._server = eventlet.spawn(**wsgi_kwargs)

    def reset(self):
        """Reset server greenpool size to default.

        :returns: None

        """
        self._pool.resize(self.pool_size)

    def stop(self):
        """Stop this server.

        This is not a very nice action, as currently the method by which a
        server is stopped is by killing its eventlet.

        :returns: None

        """
        LOG.info(_("Stopping WSGI server."))

        if self._server is not None:
            # Resize pool to stop new requests from being processed
            self._pool.resize(0)
            self._server.kill()

    def wait(self):
        """Block, until the server has stopped.

        Waits on the server's eventlet to finish, then returns.

        :returns: None

        """
        try:
            if self._server is not None:
                self._pool.waitall()
                self._server.wait()
        except greenlet.GreenletExit:
            LOG.info(_("WSGI server has stopped."))


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(explanation='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):
            return cls(app, **local_config)
        return _factory

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

    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):
        print(('*' * 40) + ' REQUEST ENVIRON')
        for key, value in req.environ.items():
            print(key, '=', value)
        print()
        resp = req.get_response(self.application)

        print(('*' * 40) + ' RESPONSE HEADERS')
        for (key, value) in resp.headers.iteritems():
            print(key, '=', value)
        print()

        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."""
        print(('*' * 40) + ' BODY')
        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


class Loader(object):
    """Used to load WSGI applications from paste configurations."""

    def __init__(self, config_path=None):
        """Initialize the loader, and attempt to find the config.

        :param config_path: Full or relative path to the paste config.
        :returns: None

        """
        self.config_path = None

        config_path = config_path or CONF.api_paste_config
        if not os.path.isabs(config_path):
            self.config_path = CONF.find_file(config_path)
        elif os.path.exists(config_path):
            self.config_path = config_path

        if not self.config_path:
            raise exception.ConfigNotFound(path=config_path)

    def load_app(self, name):
        """Return the paste URLMap wrapped WSGI application.

        :param name: Name of the application to load.
        :returns: Paste URLMap object wrapping the requested application.
        :raises: `nova.exception.PasteAppNotFound`

        """
        try:
            LOG.debug("Loading app %(name)s from %(path)s",
                      {'name': name, 'path': self.config_path})
            return deploy.loadapp("config:%s" % self.config_path, name=name)
        except LookupError as err:
            LOG.error(err)
            raise exception.PasteAppNotFound(name=name, path=self.config_path)
