# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# Copyright 2010 OpenStack Foundation
# Copyright 2014 IBM Corp.
# 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 abc
import errno
import functools
import os
import re
import signal
import struct
import subprocess
import sys
import time

from eventlet.green import socket
import eventlet.greenio
import eventlet.wsgi
import glance_store
from os_win import utilsfactory as os_win_utilsfactory
from oslo_concurrency import processutils
from oslo_config import cfg
from oslo_log import log as logging
from oslo_serialization import jsonutils
from oslo_utils import encodeutils
from oslo_utils import strutils
from osprofiler import opts as profiler_opts
import routes.middleware
import webob.dec
import webob.exc
from webob import multidict

from glance.common import config
from glance.common import exception
from glance.common import store_utils
from glance.common import utils
import glance.db
from glance import housekeeping
from glance import i18n
from glance.i18n import _, _LE, _LI, _LW


bind_opts = [
    cfg.HostAddressOpt('bind_host',
                       default='0.0.0.0',
                       help=_("""
IP address to bind the glance servers to.

Provide an IP address to bind the glance server to. The default
value is ``0.0.0.0``.

Edit this option to enable the server to listen on one particular
IP address on the network card. This facilitates selection of a
particular network interface for the server.

Possible values:
    * A valid IPv4 address
    * A valid IPv6 address

Related options:
    * None

""")),

    cfg.PortOpt('bind_port',
                help=_("""
Port number on which the server will listen.

Provide a valid port number to bind the server's socket to. This
port is then set to identify processes and forward network messages
that arrive at the server. The default bind_port value for the API
server is 9292 and for the registry server is 9191.

Possible values:
    * A valid port number (0 to 65535)

Related options:
    * None

""")),
]

socket_opts = [
    cfg.IntOpt('backlog',
               default=4096,
               min=1,
               help=_("""
Set the number of incoming connection requests.

Provide a positive integer value to limit the number of requests in
the backlog queue. The default queue size is 4096.

An incoming connection to a TCP listener socket is queued before a
connection can be established with the server. Setting the backlog
for a TCP socket ensures a limited queue size for incoming traffic.

Possible values:
    * Positive integer

Related options:
    * None

""")),

    cfg.IntOpt('tcp_keepidle',
               default=600,
               min=1,
               help=_("""
Set the wait time before a connection recheck.

Provide a positive integer value representing time in seconds which
is set as the idle wait time before a TCP keep alive packet can be
sent to the host. The default value is 600 seconds.

Setting ``tcp_keepidle`` helps verify at regular intervals that a
connection is intact and prevents frequent TCP connection
reestablishment.

Possible values:
    * Positive integer value representing time in seconds

Related options:
    * None

""")),
]

eventlet_opts = [
    cfg.IntOpt('workers',
               min=0,
               help=_("""
Number of Glance worker processes to start.

Provide a non-negative integer value to set the number of child
process workers to service requests. By default, the number of CPUs
available is set as the value for ``workers`` limited to 8. For
example if the processor count is 6, 6 workers will be used, if the
processor count is 24 only 8 workers will be used. The limit will only
apply to the default value, if 24 workers is configured, 24 is used.

Each worker process is made to listen on the port set in the
configuration file and contains a greenthread pool of size 1000.

NOTE: Setting the number of workers to zero, triggers the creation
of a single API process with a greenthread pool of size 1000.

Possible values:
    * 0
    * Positive integer value (typically equal to the number of CPUs)

Related options:
    * None

""")),

    cfg.IntOpt('max_header_line',
               default=16384,
               min=0,
               help=_("""
Maximum line size of message headers.

Provide an integer value representing a length to limit the size of
message headers. The default value is 16384.

NOTE: ``max_header_line`` may need to be increased when using large
tokens (typically those generated by the Keystone v3 API with big
service catalogs). However, it is to be kept in mind that larger
values for ``max_header_line`` would flood the logs.

Setting ``max_header_line`` to 0 sets no limit for the line size of
message headers.

Possible values:
    * 0
    * Positive integer

Related options:
    * None

""")),

    cfg.BoolOpt('http_keepalive',
                default=True,
                help=_("""
Set keep alive option for HTTP over TCP.

Provide a boolean value to determine sending of keep alive packets.
If set to ``False``, the server returns the header
"Connection: close". If set to ``True``, the server returns a
"Connection: Keep-Alive" in its responses. This enables retention of
the same TCP connection for HTTP conversations instead of opening a
new one with each new request.

This option must be set to ``False`` if the client socket connection
needs to be closed explicitly after the response is received and
read successfully by the client.

Possible values:
    * True
    * False

Related options:
    * None

""")),

    cfg.IntOpt('client_socket_timeout',
               default=900,
               min=0,
               help=_("""
Timeout for client connections' socket operations.

Provide a valid integer value representing time in seconds to set
the period of wait before an incoming connection can be closed. The
default value is 900 seconds.

The value zero implies wait forever.

Possible values:
    * Zero
    * Positive integer

Related options:
    * None

""")),
]

store_opts = [
    cfg.DictOpt('enabled_backends',
                help=_('Key:Value pair of store identifier and store type. '
                       'In case of multiple backends should be separated '
                       'using comma.')),
]

cli_opts = [
    cfg.StrOpt('pipe-handle',
               help='This argument is used internally on Windows. Glance '
                    'passes a pipe handle to child processes, which is then '
                    'used for inter-process communication.'),
]


LOG = logging.getLogger(__name__)

CONF = cfg.CONF
CONF.register_opts(bind_opts)
CONF.register_opts(socket_opts)
CONF.register_opts(eventlet_opts)
CONF.register_opts(store_opts)
profiler_opts.set_defaults(CONF)

ASYNC_EVENTLET_THREAD_POOL_LIST = []

# Detect if we're running under the uwsgi server
try:
    import uwsgi
    LOG.debug('Detected running under uwsgi')
except ImportError:
    LOG.debug('Detected not running under uwsgi')
    uwsgi = None

# Reserved file stores for staging and tasks operations
RESERVED_STORES = {
    'os_glance_staging_store': 'file',
    'os_glance_tasks_store': 'file'
}


def register_cli_opts():
    CONF.register_cli_opts(cli_opts)


def get_num_workers():
    """Return the configured number of workers."""

    # Windows only: we're already running on the worker side.
    if os.name == 'nt' and getattr(CONF, 'pipe_handle', None):
        return 0

    if CONF.workers is None:
        # None implies the number of CPUs limited to 8
        # See Launchpad bug #1748916 and the config help text
        workers = processutils.get_worker_count()
        return workers if workers < 8 else 8
    return CONF.workers


def get_bind_addr(default_port=None):
    """Return the host and port to bind to."""
    return (CONF.bind_host, CONF.bind_port or default_port)


def get_socket(default_port):
    """
    Bind socket to bind ip:port in conf

    note: Mostly comes from Swift with a few small changes...

    :param default_port: port to bind to if none is specified in conf

    :returns: a socket object as returned from socket.listen
    """
    bind_addr = get_bind_addr(default_port)

    # TODO(jaypipes): eventlet's greened socket module does not actually
    # support IPv6 in getaddrinfo(). We need to get around this in the
    # future or monitor upstream for a fix
    address_family = [
        addr[0] for addr in socket.getaddrinfo(bind_addr[0],
                                               bind_addr[1],
                                               socket.AF_UNSPEC,
                                               socket.SOCK_STREAM)
        if addr[0] in (socket.AF_INET, socket.AF_INET6)
    ][0]

    sock = utils.get_test_suite_socket()
    retry_until = time.time() + 30

    while not sock and time.time() < retry_until:
        try:
            sock = eventlet.listen(bind_addr,
                                   backlog=CONF.backlog,
                                   family=address_family)
        except socket.error as err:
            if err.args[0] != errno.EADDRINUSE:
                raise
            eventlet.sleep(0.1)
    if not sock:
        raise RuntimeError(_("Could not bind to %(host)s:%(port)s after"
                             " trying for 30 seconds") %
                           {'host': bind_addr[0],
                            'port': bind_addr[1]})

    return sock


def set_eventlet_hub():
    try:
        eventlet.hubs.use_hub('poll')
    except Exception:
        try:
            eventlet.hubs.use_hub('selects')
        except Exception:
            msg = _("eventlet 'poll' nor 'selects' hubs are available "
                    "on this platform")
            raise exception.WorkerCreationFailure(
                reason=msg)


def initialize_glance_store():
    """Initialize glance store."""
    glance_store.register_opts(CONF)
    glance_store.create_stores(CONF)
    glance_store.verify_default_store()


def initialize_multi_store():
    """Initialize glance multi store backends."""
    glance_store.register_store_opts(CONF, reserved_stores=RESERVED_STORES)
    glance_store.create_multi_stores(CONF, reserved_stores=RESERVED_STORES)
    glance_store.verify_store()


def get_asynchronous_eventlet_pool(size=1000):
    """Return eventlet pool to caller.

    Also store pools created in global list, to wait on
    it after getting signal for graceful shutdown.

    :param size: eventlet pool size
    :returns: eventlet pool
    """
    global ASYNC_EVENTLET_THREAD_POOL_LIST

    pool = eventlet.GreenPool(size=size)
    # Add pool to global ASYNC_EVENTLET_THREAD_POOL_LIST
    ASYNC_EVENTLET_THREAD_POOL_LIST.append(pool)

    return pool


class BaseServer(metaclass=abc.ABCMeta):
    """Server class to manage multiple WSGI sockets and applications.

    This class requires initialize_glance_store set to True if
    glance store needs to be initialized.
    """
    def __init__(self, threads=1000, initialize_glance_store=False):
        os.umask(0o27)  # ensure files are created with the correct privileges
        self._logger = logging.getLogger("eventlet.wsgi.server")
        self.threads = threads
        self.children = set()
        self.stale_children = set()
        self.running = True
        # NOTE(abhishek): Allows us to only re-initialize glance_store when
        # the API's configuration reloads.
        self.initialize_glance_store = initialize_glance_store

    @staticmethod
    def set_signal_handler(signal_name, handler):
        # Some signals may not be available on this platform.
        sig = getattr(signal, signal_name, None)
        if sig is not None:
            signal.signal(sig, handler)

    def hup(self, *args):
        """
        Reloads configuration files with zero down time
        """
        self.set_signal_handler("SIGHUP", signal.SIG_IGN)
        raise exception.SIGHUPInterrupt

    @abc.abstractmethod
    def kill_children(self, *args):
        pass

    @abc.abstractmethod
    def wait_on_children(self):
        pass

    @abc.abstractmethod
    def run_child(self):
        pass

    def reload(self):
        raise NotImplementedError()

    def start(self, application, default_port):
        """
        Run a WSGI server with the given application.

        :param application: The application to be run in the WSGI server
        :param default_port: Port to bind to if none is specified in conf
        """
        self.application = application
        self.default_port = default_port
        self.configure()
        self.start_wsgi()

        cleaner = housekeeping.StagingStoreCleaner(glance.db.get_api())
        self.pool.spawn_n(cleaner.clean_orphaned_staging_residue)

    def start_wsgi(self):
        workers = get_num_workers()
        self.pool = self.create_pool()
        if workers == 0:
            # Useful for profiling, test, debug etc.
            self.pool.spawn_n(self._single_run, self.application, self.sock)
            return
        else:
            LOG.info(_LI("Starting %d workers"), workers)
            self.set_signal_handler("SIGTERM", self.kill_children)
            self.set_signal_handler("SIGINT", self.kill_children)
            self.set_signal_handler("SIGHUP", self.hup)
            while len(self.children) < workers:
                self.run_child()

    def create_pool(self):
        return get_asynchronous_eventlet_pool(size=self.threads)

    def configure(self, old_conf=None, has_changed=None):
        """
        Apply configuration settings

        :param old_conf: Cached old configuration settings (if any)
        :param has changed: callable to determine if a parameter has changed
        """
        eventlet.wsgi.MAX_HEADER_LINE = CONF.max_header_line
        self.client_socket_timeout = CONF.client_socket_timeout or None
        if self.initialize_glance_store:
            if CONF.enabled_backends:
                if store_utils.check_reserved_stores(CONF.enabled_backends):
                    msg = _("'os_glance_' prefix should not be used in "
                            "enabled_backends config option. It is reserved "
                            "for internal use only.")
                    raise RuntimeError(msg)
                initialize_multi_store()
            else:
                initialize_glance_store()
        self.configure_socket(old_conf, has_changed)

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

    def run_server(self):
        """Run a WSGI server."""
        if cfg.CONF.pydev_worker_debug_host:
            utils.setup_remote_pydev_debug(cfg.CONF.pydev_worker_debug_host,
                                           cfg.CONF.pydev_worker_debug_port)

        eventlet.wsgi.HttpProtocol.default_request_version = "HTTP/1.0"
        self.pool = self.create_pool()
        try:
            eventlet.wsgi.server(self.sock,
                                 self.application,
                                 log=self._logger,
                                 custom_pool=self.pool,
                                 debug=False,
                                 keepalive=CONF.http_keepalive,
                                 socket_timeout=self.client_socket_timeout)
        except socket.error as err:
            if err[0] != errno.EINVAL:
                raise

        # waiting on async pools
        if ASYNC_EVENTLET_THREAD_POOL_LIST:
            for pool in ASYNC_EVENTLET_THREAD_POOL_LIST:
                pool.waitall()

        # NOTE(abhishekk): Importing the cache_images API module just
        #  in time to avoid partial initialization of wsgi module
        from glance.api.v2 import cached_images  # noqa
        if cached_images.WORKER:
            # If we started a cache worker, signal it to exit
            # and wait until it does.
            cached_images.WORKER.terminate()

    def _single_run(self, application, sock):
        """Start a WSGI server in a new green thread."""
        LOG.info(_LI("Starting single process server"))
        eventlet.wsgi.server(sock, application, custom_pool=self.pool,
                             log=self._logger,
                             debug=False,
                             keepalive=CONF.http_keepalive,
                             socket_timeout=self.client_socket_timeout)

    def configure_socket(self, old_conf=None, has_changed=None):
        """
        Ensure a socket exists and is appropriately configured.

        This function is called on start up, and can also be
        called in the event of a configuration reload.

        When called for the first time a new socket is created.
        If reloading and either bind_host or bind port have been
        changed the existing socket must be closed and a new
        socket opened (laws of physics).

        In all other cases (bind_host/bind_port have not changed)
        the existing socket is reused.

        :param old_conf: Cached old configuration settings (if any)
        :param has changed: callable to determine if a parameter has changed
        """
        # Do we need a fresh socket?
        new_sock = (old_conf is None or (
                    has_changed('bind_host') or
                    has_changed('bind_port')))

        if new_sock:
            self._sock = None
            if old_conf is not None:
                self.sock.close()
            _sock = get_socket(self.default_port)
            _sock.setsockopt(socket.SOL_SOCKET,
                             socket.SO_REUSEADDR, 1)
            # sockets can hang around forever without keepalive
            _sock.setsockopt(socket.SOL_SOCKET,
                             socket.SO_KEEPALIVE, 1)
            self.sock = _sock

        if new_sock or (old_conf is not None and has_changed('tcp_keepidle')):
            # This option isn't available in the OS X version of eventlet
            if hasattr(socket, 'TCP_KEEPIDLE'):
                self.sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPIDLE,
                                     CONF.tcp_keepidle)

        if old_conf is not None and has_changed('backlog'):
            self.sock.listen(CONF.backlog)


class PosixServer(BaseServer):
    def __init__(self, *args, **kwargs):
        super(PosixServer, self).__init__(*args, **kwargs)

        self.pgid = os.getpid()
        try:
            # NOTE(flaper87): Make sure this process
            # runs in its own process group.
            os.setpgid(self.pgid, self.pgid)
        except OSError:
            # NOTE(flaper87): When running glance-control,
            # (glance's functional tests, for example)
            # setpgid fails with EPERM as glance-control
            # creates a fresh session, of which the newly
            # launched service becomes the leader (session
            # leaders may not change process groups)
            #
            # Running glance-(api|registry) is safe and
            # shouldn't raise any error here.
            self.pgid = 0

    def kill_children(self, *args):
        """Kills the entire process group."""
        self.set_signal_handler("SIGTERM", signal.SIG_IGN)
        self.set_signal_handler("SIGINT", signal.SIG_IGN)
        self.set_signal_handler("SIGCHLD", signal.SIG_IGN)
        self.running = False
        os.killpg(self.pgid, signal.SIGTERM)

    def _remove_children(self, pid):
        if pid in self.children:
            self.children.remove(pid)
            LOG.info(_LI('Removed dead child %s'), pid)
        elif pid in self.stale_children:
            self.stale_children.remove(pid)
            LOG.info(_LI('Removed stale child %s'), pid)
        else:
            LOG.warning(_LW('Unrecognised child %s'), pid)

    def _verify_and_respawn_children(self, pid, status):
        if len(self.stale_children) == 0:
            LOG.debug('No stale children')
        if os.WIFEXITED(status) and os.WEXITSTATUS(status) != 0:
            LOG.error(_LE('Not respawning child %d, cannot '
                          'recover from termination'), pid)
            if not self.children and not self.stale_children:
                LOG.info(
                    _LI('All workers have terminated. Exiting'))
                self.running = False
        else:
            if len(self.children) < get_num_workers():
                self.run_child()

    def wait_on_children(self):
        while self.running:
            try:
                pid, status = os.wait()
                if os.WIFEXITED(status) or os.WIFSIGNALED(status):
                    self._remove_children(pid)
                    self._verify_and_respawn_children(pid, status)
            except OSError as err:
                if err.errno not in (errno.EINTR, errno.ECHILD):
                    raise
            except KeyboardInterrupt:
                LOG.info(_LI('Caught keyboard interrupt. Exiting.'))
                break
            except exception.SIGHUPInterrupt:
                self.reload()
                continue
        eventlet.greenio.shutdown_safe(self.sock)
        self.sock.close()
        LOG.debug('Exited')

    def run_child(self):
        def child_hup(*args):
            """Shuts down child processes, existing requests are handled."""
            self.set_signal_handler("SIGHUP", signal.SIG_IGN)
            eventlet.wsgi.is_accepting = False
            self.sock.close()

        pid = os.fork()
        if pid == 0:
            self.set_signal_handler("SIGHUP", child_hup)
            self.set_signal_handler("SIGTERM", signal.SIG_DFL)
            # ignore the interrupt signal to avoid a race whereby
            # a child worker receives the signal before the parent
            # and is respawned unnecessarily as a result
            self.set_signal_handler("SIGINT", signal.SIG_IGN)
            # The child has no need to stash the unwrapped
            # socket, and the reference prevents a clean
            # exit on sighup
            self._sock = None
            self.run_server()
            LOG.info(_LI('Child %d exiting normally'), os.getpid())
            # self.pool.waitall() is now called in wsgi's server so
            # it's safe to exit here
            sys.exit(0)
        else:
            LOG.info(_LI('Started child %s'), pid)
            self.children.add(pid)

    def reload(self):
        """
        Reload and re-apply configuration settings

        Existing child processes are sent a SIGHUP signal
        and will exit after completing existing requests.
        New child processes, which will have the updated
        configuration, are spawned. This allows preventing
        interruption to the service.
        """
        def _has_changed(old, new, param):
            old = old.get(param)
            new = getattr(new, param)
            return (new != old)

        old_conf = utils.stash_conf_values()
        has_changed = functools.partial(_has_changed, old_conf, CONF)
        CONF.reload_config_files()
        os.killpg(self.pgid, signal.SIGHUP)
        self.stale_children = self.children
        self.children = set()

        # Ensure any logging config changes are picked up
        logging.setup(CONF, 'glance')
        config.set_config_defaults()

        self.configure(old_conf, has_changed)
        self.start_wsgi()


class Win32ProcessLauncher(object):
    def __init__(self):
        self._processutils = os_win_utilsfactory.get_processutils()

        self._workers = []
        self._worker_job_handles = []

    def add_process(self, cmd):
        LOG.info("Starting subprocess: %s", cmd)

        worker = subprocess.Popen(cmd, close_fds=False)
        try:
            job_handle = self._processutils.kill_process_on_job_close(
                worker.pid)
        except Exception:
            LOG.exception("Could not associate child process "
                          "with a job, killing it.")
            worker.kill()
            raise

        self._worker_job_handles.append(job_handle)
        self._workers.append(worker)

        return worker

    def wait(self):
        pids = [worker.pid for worker in self._workers]
        if pids:
            self._processutils.wait_for_multiple_processes(pids,
                                                           wait_all=True)
        # By sleeping here, we allow signal handlers to be executed.
        time.sleep(0)


class Win32Server(BaseServer):
    _py_script_re = re.compile(r'.*\.py\w?$')
    _sock = None

    def __init__(self, *args, **kwargs):
        super(Win32Server, self).__init__(*args, **kwargs)
        self._launcher = Win32ProcessLauncher()
        self._ioutils = os_win_utilsfactory.get_ioutils()

    def run_child(self):
        # We're passing copies of the socket through pipes.
        rfd, wfd = self._ioutils.create_pipe(inherit_handle=True)

        cmd = sys.argv + ['--pipe-handle=%s' % int(rfd)]
        # Recent setuptools versions will trim '-script.py' and '.exe'
        # extensions from sys.argv[0].
        if self._py_script_re.match(sys.argv[0]):
            cmd = [sys.executable] + cmd

        worker = self._launcher.add_process(cmd)
        self._ioutils.close_handle(rfd)

        share_sock_buff = self._sock.share(worker.pid)
        self._ioutils.write_file(
            wfd,
            struct.pack('<I', len(share_sock_buff)),
            4)
        self._ioutils.write_file(
            wfd, share_sock_buff, len(share_sock_buff))

        self.children.add(worker.pid)

    def kill_children(self, *args):
        # We're using job objects, the children will exit along with the
        # main process.
        exit(0)

    def wait_on_children(self):
        self._launcher.wait()

    def _get_sock_from_parent(self):
        # This is supposed to be called exactly once in the child process.
        # We're passing a copy of the socket through a pipe.
        pipe_handle = int(getattr(CONF, 'pipe_handle', 0))
        if not pipe_handle:
            err_msg = _("Did not receive a pipe handle, which is used when "
                        "communicating with the parent process.")
            raise exception.GlanceException(err_msg)

        # Get the length of the data to be received.
        buff = self._ioutils.get_buffer(4)
        self._ioutils.read_file(pipe_handle, buff, 4)
        socket_buff_sz = struct.unpack('<I', buff)[0]

        # Get the serialized socket object.
        socket_buff = self._ioutils.get_buffer(socket_buff_sz)
        self._ioutils.read_file(pipe_handle, socket_buff, socket_buff_sz)
        self._ioutils.close_handle(pipe_handle)

        # Recreate the socket object. This will only work with
        # Python 3.6 or later.
        return socket.fromshare(bytes(socket_buff[:]))

    def configure_socket(self, old_conf=None, has_changed=None):
        fresh_start = not (old_conf or has_changed)
        pipe_handle = getattr(CONF, 'pipe_handle', None)

        if not (fresh_start and pipe_handle):
            return super(Win32Server, self).configure_socket(
                old_conf, has_changed)

        self.sock = self._get_sock_from_parent()

        if hasattr(socket, 'TCP_KEEPIDLE'):
            # This was introduced in WS 2016 RS3
            self.sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPIDLE,
                                 CONF.tcp_keepidle)


if os.name == 'nt':
    Server = Win32Server
else:
    Server = PosixServer


class Middleware(object):
    """
    Base WSGI middleware wrapper. 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.
    """

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

    @classmethod
    def factory(cls, global_conf, **local_conf):
        def filter(app):
            return cls(app)
        return filter

    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
    def __call__(self, req):
        response = self.process_request(req)
        if response:
            return response
        response = req.get_response(self.application)
        response.request = req
        try:
            return self.process_response(response)
        except webob.exc.HTTPException as e:
            return e


class Debug(Middleware):
    """
    Helper class that can be inserted into any WSGI application chain
    to get information about the request and response.
    """

    @webob.dec.wsgify
    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 iterator
        when iterated.
        """
        print(("*" * 40) + " BODY")
        for part in app_iter:
            sys.stdout.write(part)
            sys.stdout.flush()
            yield part
        print()


class APIMapper(routes.Mapper):
    """
    Handle route matching when url is '' because routes.Mapper returns
    an error in this case.
    """

    def routematch(self, url=None, environ=None):
        if url == "":
            result = self._match("", environ)
            return result[0], result[1]
        return routes.Mapper.routematch(self, url, environ)


class RejectMethodController(object):
    def reject(self, req, allowed_methods, *args, **kwargs):
        LOG.debug("The method %s is not allowed for this resource",
                  req.environ['REQUEST_METHOD'])
        raise webob.exc.HTTPMethodNotAllowed(
            headers=[('Allow', allowed_methods)])


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 a wsgi.Controller, who will route
        the request to the action 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())
        """
        mapper.redirect("", "/")
        self.map = mapper
        self._router = routes.middleware.RoutesMiddleware(self._dispatch,
                                                          self.map)

    @classmethod
    def factory(cls, global_conf, **local_conf):
        return cls(APIMapper())

    @webob.dec.wsgify
    def __call__(self, req):
        """
        Route the incoming request to a controller based on self.map.
        If no match, return either a 404(Not Found) or 501(Not Implemented).
        """
        return self._router

    @staticmethod
    @webob.dec.wsgify
    def _dispatch(req):
        """
        Called by self._router after matching the incoming request to a route
        and putting the information into req.environ.  Either returns 404,
        501, or the routed WSGI app's response.
        """
        match = req.environ['wsgiorg.routing_args'][1]
        if not match:
            implemented_http_methods = ['GET', 'HEAD', 'POST', 'PUT',
                                        'DELETE', 'PATCH']
            if req.environ['REQUEST_METHOD'] not in implemented_http_methods:
                return webob.exc.HTTPNotImplemented()
            else:
                return webob.exc.HTTPNotFound()
        app = match['controller']
        return app


class _UWSGIChunkFile(object):

    def read(self, length=None):
        position = 0
        if length == 0:
            return b""

        if length and length < 0:
            length = None

        response = []
        while True:
            data = uwsgi.chunked_read()
            # Return everything if we reached the end of the file
            if not data:
                break
            response.append(data)
            # Return the data if we've reached the length
            if length is not None:
                position += len(data)
                if position >= length:
                    break
        return b''.join(response)


class Request(webob.Request):
    """Add some OpenStack API-specific logic to the base webob.Request."""

    def __init__(self, environ, *args, **kwargs):
        super(Request, self).__init__(environ, *args, **kwargs)

    @property
    def body_file(self):
        if uwsgi:
            if self.headers.get('transfer-encoding', '').lower() == 'chunked':
                return _UWSGIChunkFile()
        return super(Request, self).body_file

    @body_file.setter
    def body_file(self, value):
        # NOTE(cdent): If you have a property setter in a superclass, it will
        # not be inherited.
        webob.Request.body_file.fset(self, value)

    def best_match_content_type(self):
        """Determine the requested response content-type."""
        supported = ('application/json',)
        best_matches = self.accept.acceptable_offers(supported)
        if not best_matches:
            return 'application/json'
        return best_matches[0][0]

    def get_content_type(self, allowed_content_types):
        """Determine content type of the request body."""
        if "Content-Type" not in self.headers:
            raise exception.InvalidContentType(content_type=None)

        content_type = self.content_type

        if content_type not in allowed_content_types:
            raise exception.InvalidContentType(content_type=content_type)
        else:
            return content_type

    def best_match_language(self):
        """Determines best available locale from the Accept-Language header.

        :returns: the best language match or None if the 'Accept-Language'
                  header was not available in the request.
        """
        if not self.accept_language:
            return None
        langs = i18n.get_available_languages('glance')
        # NOTE(rosmaita): give the webob lookup() function a sentinel value
        # for default so we can preserve the behavior of this function as
        # indicated by the current unit tests.  See Launchpad bug #1765748.
        best_match = self.accept_language.lookup(langs, default='fake_LANG')
        if best_match == 'fake_LANG':
            best_match = None
        return best_match

    def get_range_from_request(self, image_size):
        """Return the `Range` in a request."""

        range_str = self.headers.get('Range')
        if range_str is not None:

            # NOTE(dharinic): We do not support multi range requests.
            if ',' in range_str:
                msg = ("Requests with multiple ranges are not supported in "
                       "Glance. You may make multiple single-range requests "
                       "instead.")
                raise webob.exc.HTTPBadRequest(explanation=msg)

            range_ = webob.byterange.Range.parse(range_str)
            if range_ is None:
                msg = ("Invalid Range header.")
                raise webob.exc.HTTPRequestRangeNotSatisfiable(msg)
            # NOTE(dharinic): Ensure that a range like bytes=4- for an image
            # size of 3 is invalidated as per rfc7233.
            if range_.start >= image_size:
                msg = ("Invalid start position in Range header. "
                       "Start position MUST be in the inclusive range [0, %s]."
                       % (image_size - 1))
                raise webob.exc.HTTPRequestRangeNotSatisfiable(msg)
            return range_

        # NOTE(dharinic): For backward compatibility reasons, we maintain
        # support for 'Content-Range' in requests even though it's not
        # correct to use it in requests..
        c_range_str = self.headers.get('Content-Range')
        if c_range_str is not None:
            content_range = webob.byterange.ContentRange.parse(c_range_str)
            # NOTE(dharinic): Ensure that a content range like 1-4/* for an
            # image size of 3 is invalidated.
            if content_range is None:
                msg = ("Invalid Content-Range header.")
                raise webob.exc.HTTPRequestRangeNotSatisfiable(msg)
            if (content_range.length is None and
                    content_range.stop > image_size):
                msg = ("Invalid stop position in Content-Range header. "
                       "The stop position MUST be in the inclusive range "
                       "[0, %s]." % (image_size - 1))
                raise webob.exc.HTTPRequestRangeNotSatisfiable(msg)
            if content_range.start >= image_size:
                msg = ("Invalid start position in Content-Range header. "
                       "Start position MUST be in the inclusive range [0, %s]."
                       % (image_size - 1))
                raise webob.exc.HTTPRequestRangeNotSatisfiable(msg)
            return content_range


class JSONRequestDeserializer(object):
    valid_transfer_encoding = frozenset(['chunked', 'compress', 'deflate',
                                         'gzip', 'identity'])
    httpverb_may_have_body = frozenset({'POST', 'PUT', 'PATCH'})

    @classmethod
    def is_valid_encoding(cls, request):
        request_encoding = request.headers.get('transfer-encoding', '').lower()
        return request_encoding in cls.valid_transfer_encoding

    @classmethod
    def is_valid_method(cls, request):
        return request.method.upper() in cls.httpverb_may_have_body

    def has_body(self, request):
        """
        Returns whether a Webob.Request object will possess an entity body.

        :param request:  Webob.Request object
        """

        if self.is_valid_encoding(request) and self.is_valid_method(request):
            request.is_body_readable = True
            return True

        if request.content_length is not None and request.content_length > 0:
            return True

        return False

    @staticmethod
    def _sanitizer(obj):
        """Sanitizer method that will be passed to jsonutils.loads."""
        return obj

    def from_json(self, datastring):
        try:
            jsondata = jsonutils.loads(datastring, object_hook=self._sanitizer)
            if not isinstance(jsondata, (dict, list)):
                msg = _('Unexpected body type. Expected list/dict.')
                raise webob.exc.HTTPBadRequest(explanation=msg)
            return jsondata
        except ValueError:
            msg = _('Malformed JSON in request body.')
            raise webob.exc.HTTPBadRequest(explanation=msg)

    def default(self, request):
        if self.has_body(request):
            return {'body': self.from_json(request.body)}
        else:
            return {}


class JSONResponseSerializer(object):

    def _sanitizer(self, obj):
        """Sanitizer method that will be passed to jsonutils.dumps."""
        if hasattr(obj, "to_dict"):
            return obj.to_dict()
        if isinstance(obj, multidict.MultiDict):
            return obj.mixed()
        return jsonutils.to_primitive(obj)

    def to_json(self, data):
        return jsonutils.dump_as_bytes(data, default=self._sanitizer)

    def default(self, response, result):
        response.content_type = 'application/json'
        body = self.to_json(result)
        body = encodeutils.to_utf8(body)
        response.body = body


def translate_exception(req, e):
    """Translates all translatable elements of the given exception."""

    # The RequestClass attribute in the webob.dec.wsgify decorator
    # does not guarantee that the request object will be a particular
    # type; this check is therefore necessary.
    if not hasattr(req, "best_match_language"):
        return e

    locale = req.best_match_language()

    if isinstance(e, webob.exc.HTTPError):
        e.explanation = i18n.translate(e.explanation, locale)
        e.detail = i18n.translate(e.detail, locale)
        if getattr(e, 'body_template', None):
            e.body_template = i18n.translate(e.body_template, locale)
    return e


class Resource(object):
    """
    WSGI app that handles (de)serialization and controller dispatch.

    Reads routing information supplied by RoutesMiddleware and calls
    the requested action method upon its deserializer, controller,
    and serializer. Those three objects may implement any of the basic
    controller action methods (create, update, show, index, delete)
    along with any that may be specified in the api router. A 'default'
    method may also be implemented to be used in place of any
    non-implemented actions. Deserializer methods must accept a request
    argument and return a dictionary. Controller methods must accept a
    request argument. Additionally, they must also accept keyword
    arguments that represent the keys returned by the Deserializer. They
    may raise a webob.exc exception or return a dict, which will be
    serialized by requested content type.
    """

    def __init__(self, controller, deserializer=None, serializer=None):
        """
        :param controller: object that implement methods created by routes lib
        :param deserializer: object that supports webob request deserialization
                             through controller-like actions
        :param serializer: object that supports webob response serialization
                           through controller-like actions
        """
        self.controller = controller
        self.serializer = serializer or JSONResponseSerializer()
        self.deserializer = deserializer or JSONRequestDeserializer()

    @webob.dec.wsgify(RequestClass=Request)
    def __call__(self, request):
        """WSGI method that controls (de)serialization and method dispatch."""
        action_args = self.get_action_args(request.environ)
        action = action_args.pop('action', None)
        body_reject = strutils.bool_from_string(
            action_args.pop('body_reject', None))

        try:
            if body_reject and self.deserializer.has_body(request):
                msg = _('A body is not expected with this request.')
                raise webob.exc.HTTPBadRequest(explanation=msg)
            deserialized_request = self.dispatch(self.deserializer,
                                                 action, request)
            action_args.update(deserialized_request)
            action_result = self.dispatch(self.controller, action,
                                          request, **action_args)
        except webob.exc.WSGIHTTPException as e:
            e = translate_exception(request, e)
            raise e.with_traceback(sys.exc_info()[2])
        except UnicodeDecodeError:
            msg = _("Error decoding your request. Either the URL or the "
                    "request body contained characters that could not be "
                    "decoded by Glance")
            raise webob.exc.HTTPBadRequest(explanation=msg)
        except exception.InvalidPropertyProtectionConfiguration as e:
            LOG.exception(_LE("Caught error: %s"),
                          encodeutils.exception_to_unicode(e))
            raise webob.exc.HTTPBadRequest(explanation=e.msg)
        except Exception as e:
            LOG.exception(_LE("Caught error: %s"),
                          encodeutils.exception_to_unicode(e))
            response = webob.exc.HTTPInternalServerError()
            return response

        # We cannot serialize an Exception, so return the action_result
        if isinstance(action_result, Exception):
            return action_result

        try:
            response = webob.Response(request=request)
            self.dispatch(self.serializer, action, response, action_result)
            return response
        except webob.exc.WSGIHTTPException as e:
            return translate_exception(request, e)
        except webob.exc.HTTPException as e:
            return e
        # return unserializable result (typically a webob exc)
        except Exception:
            return action_result

    def dispatch(self, obj, action, *args, **kwargs):
        """Find action-specific method on self and call it."""
        try:
            method = getattr(obj, action)
        except AttributeError:
            method = getattr(obj, 'default')

        return method(*args, **kwargs)

    def get_action_args(self, request_environment):
        """Parse dictionary created by routes library."""
        try:
            args = request_environment['wsgiorg.routing_args'][1].copy()
        except Exception:
            return {}

        try:
            del args['controller']
        except KeyError:
            pass

        try:
            del args['format']
        except KeyError:
            pass

        return args
