# Copyright (c) 2016 NTT DATA
#
#    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 os.path
import socket
import ssl
import sys

import eventlet
import eventlet.wsgi
import greenlet
from oslo_log import log as logging
from oslo_service import service
from oslo_utils import excutils
from paste import deploy
import routes.middleware
import webob.dec
import webob.exc

import masakari.conf
from masakari import exception
from masakari.i18n import _
from masakari import utils

CONF = masakari.conf.CONF

LOG = logging.getLogger(__name__)


class Server(service.ServiceBase):
    """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: masakari.exception.InvalidInput
        """
        # Allow operators to customize http requests max header line size.
        eventlet.wsgi.MAX_HEADER_LINE = CONF.wsgi.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("masakari.%s.wsgi.server" % self.name)
        self._use_ssl = use_ssl
        self._max_url_len = max_url_len

        self.client_socket_timeout = CONF.wsgi.client_socket_timeout or None

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

        bind_addr = (host, port)
        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("Could not bind to %(host)s:%(port)d",
                      {'host': host, 'port': port})
            raise

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

        if self._use_ssl:
            try:
                ca_file = CONF.wsgi.ssl_ca_file
                cert_file = CONF.wsgi.ssl_cert_file
                key_file = CONF.wsgi.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.wsgi.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)
            except Exception:
                with excutils.save_and_reraise_exception():
                    LOG.error("Failed to start %(name)s on %(host)s"
                              ":%(port)d 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._logger,
            'log_format': CONF.wsgi.wsgi_log_format,
            'debug': False,
            'keepalive': 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 = utils.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):
    def __init__(self, environ, *args, **kwargs):
        if CONF.wsgi.secure_proxy_ssl_header:
            scheme = environ.get(CONF.wsgi.secure_proxy_ssl_header)
            if scheme:
                environ['wsgi.url_scheme'] = scheme
        super(Request, self).__init__(environ, *args, **kwargs)


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 = masakari.api.fancy_api:Wadl.factory

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

            import masakari.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 ...)
          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 = masakari.api.analytics:Analytics.factory

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

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