# 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."""

import copy
import os
import socket

import eventlet
import eventlet.wsgi
import greenlet
from paste import deploy
import routes.middleware
import webob.dec
import webob.exc

from oslo_log import log as logging
from oslo_service._i18n import _
from oslo_service import _options
from oslo_service import service
from oslo_service import sslutils


LOG = logging.getLogger(__name__)


def list_opts():
    """Entry point for oslo-config-generator."""
    return [(None, copy.deepcopy(_options.wsgi_opts))]


def register_opts(conf):
    """Registers WSGI config options."""
    return conf.register_opts(_options.wsgi_opts)


class InvalidInput(Exception):
    message = _("Invalid input received: "
                "Unexpected argument for periodic task creation: %(arg)s.")


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

    # TODO(eezhova): Consider changing the default host value to prevent
    # possible binding to all interfaces. The most appropriate value seems
    # to be 127.0.0.1, but it has to be verified that the change wouldn't
    # break any consuming project.
    def __init__(self, conf, name, app, host='0.0.0.0', port=0,  # nosec
                 pool_size=None, protocol=eventlet.wsgi.HttpProtocol,
                 backlog=128, use_ssl=False, max_url_len=None,
                 logger_name='eventlet.wsgi.server',
                 socket_family=None, socket_file=None, socket_mode=None):
        """Initialize, but do not start, a WSGI server.

        :param conf: Instance of ConfigOpts.
        :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 protocol: Protocol class.
        :param backlog: Maximum number of queued connections.
        :param use_ssl: Wraps the socket in an SSL context if True.
        :param max_url_len: Maximum length of permitted URLs.
        :param logger_name: The name for the logger.
        :param socket_family: Socket family.
        :param socket_file: location of UNIX socket.
        :param socket_mode: UNIX socket mode.
        :returns: None
        :raises: InvalidInput
        :raises: EnvironmentError
        """

        self.conf = conf
        self.conf.register_opts(_options.wsgi_opts)

        self.default_pool_size = self.conf.wsgi_default_pool_size

        # 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(logger_name)
        self._use_ssl = use_ssl
        self._max_url_len = max_url_len
        self.client_socket_timeout = conf.client_socket_timeout or None

        if backlog < 1:
            raise InvalidInput(reason=_('The backlog must be more than 0'))

        if not socket_family or socket_family in [socket.AF_INET,
                                                  socket.AF_INET6]:
            self.socket = self._get_socket(host, port, backlog)
        elif hasattr(socket, "AF_UNIX") and socket_family == socket.AF_UNIX:
            self.socket = self._get_unix_socket(socket_file, socket_mode,
                                                backlog)
        else:
            raise ValueError(_("Unsupported socket family: %s"), socket_family)

        (self.host, self.port) = self.socket.getsockname()[0:2]

        if self._use_ssl:
            sslutils.is_enabled(conf)

    def _get_socket(self, host, port, backlog):
        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:
            sock = eventlet.listen(bind_addr, family, backlog=backlog)
        except EnvironmentError:
            LOG.error("Could not bind to %(host)s:%(port)s",
                      {'host': host, 'port': port})
            raise
        sock = self._set_socket_opts(sock)
        LOG.info("%(name)s listening on %(host)s:%(port)s",
                 {'name': self.name, 'host': host, 'port': port})
        return sock

    def _get_unix_socket(self, socket_file, socket_mode, backlog):
        sock = eventlet.listen(socket_file, family=socket.AF_UNIX,
                               backlog=backlog)
        if socket_mode is not None:
            os.chmod(socket_file, socket_mode)
        LOG.info("%(name)s listening on %(socket_file)s:",
                 {'name': self.name, 'socket_file': socket_file})
        return sock

    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.

        self.dup_socket = self.socket.dup()

        if self._use_ssl:
            self.dup_socket = sslutils.wrap(self.conf, self.dup_socket)

        wsgi_kwargs = {
            'func': eventlet.wsgi.server,
            'sock': self.dup_socket,
            'site': self.app,
            'protocol': self._protocol,
            'custom_pool': self._pool,
            'log': self._logger,
            'log_format': self.conf.wsgi_log_format,
            'debug': self.conf.wsgi_server_debug,
            'keepalive': self.conf.wsgi_keep_alive,
            'socket_timeout': self.client_socket_timeout
            }

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

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

    def _set_socket_opts(self, _socket):
        _socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        # sockets can hang around forever without keepalive
        _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'):
            _socket.setsockopt(socket.IPPROTO_TCP,
                               socket.TCP_KEEPIDLE,
                               self.conf.tcp_keepidle)

        return _socket

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

        :returns: None

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

    def stop(self):
        """Stops eventlet server. Doesn't allow accept new connecting.

        :returns: None

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

        if self._server is not None:
            # let eventlet close socket
            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:
                num = self._pool.running()
                LOG.debug("Waiting WSGI server to finish %d requests.", num)
                self._pool.waitall()
        except greenlet.GreenletExit:
            LOG.info("WSGI server has stopped.")


class Request(webob.Request):
    pass


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 ConfigNotFound(Exception):
    def __init__(self, path):
        msg = _('Could not find config at %(path)s') % {'path': path}
        super(ConfigNotFound, self).__init__(msg)


class PasteAppNotFound(Exception):
    def __init__(self, name, path):
        msg = (_("Could not load paste app '%(name)s' from %(path)s") %
               {'name': name, 'path': path})
        super(PasteAppNotFound, self).__init__(msg)


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

    def __init__(self, conf):
        """Initialize the loader, and attempt to find the config.

        :param conf: Application config
        :returns: None

        """
        conf.register_opts(_options.wsgi_opts)
        self.config_path = None

        config_path = 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 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: 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:
            LOG.exception("Couldn't lookup app: %s", name)
            raise PasteAppNotFound(name=name, path=self.config_path)
