# Copyright (c) 2012 Red Hat, Inc.
#
#    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.

"""
Request Body limiting middleware.

"""

from oslo_config import cfg
import webob.dec
import webob.exc

from oslo_middleware._i18n import _
from oslo_middleware import base


_oldopts = [cfg.DeprecatedOpt('osapi_max_request_body_size',
                              group='DEFAULT'),
            cfg.DeprecatedOpt('max_request_body_size',
                              group='DEFAULT')]

_opts = [
    # default request size is 112k
    cfg.IntOpt('max_request_body_size',
               default=114688,
               help='The maximum body size for each '
                    ' request, in bytes.',
               deprecated_opts=_oldopts)
]


class LimitingReader(object):
    """Reader to limit the size of an incoming request."""
    def __init__(self, data, limit):
        """Initiates LimitingReader object.

        :param data: Underlying data object
        :param limit: maximum number of bytes the reader should allow
        """
        self.data = data
        self.limit = limit
        self.bytes_read = 0

    def __iter__(self):
        for chunk in self.data:
            self.bytes_read += len(chunk)
            if self.bytes_read > self.limit:
                msg = _("Request is too large.")
                raise webob.exc.HTTPRequestEntityTooLarge(explanation=msg)
            else:
                yield chunk

    def read(self, i=None):
        # NOTE(jamielennox): We can't simply provide the default to the read()
        # call as the expected default differs between mod_wsgi and eventlet
        if i is None:
            result = self.data.read()
        else:
            result = self.data.read(i)
        self.bytes_read += len(result)
        if self.bytes_read > self.limit:
            msg = _("Request is too large.")
            raise webob.exc.HTTPRequestEntityTooLarge(explanation=msg)
        return result


class RequestBodySizeLimiter(base.ConfigurableMiddleware):
    """Limit the size of incoming requests."""

    def __init__(self, application, conf=None):
        super(RequestBodySizeLimiter, self).__init__(application, conf)
        self.oslo_conf.register_opts(_opts, group='oslo_middleware')

    @webob.dec.wsgify
    def __call__(self, req):
        max_size = self._conf_get('max_request_body_size')
        if (req.content_length is not None and
                req.content_length > max_size):
            msg = _("Request is too large.")
            raise webob.exc.HTTPRequestEntityTooLarge(explanation=msg)
        if req.content_length is None and req.is_body_readable:
            limiter = LimitingReader(req.body_file, max_size)
            req.body_file = limiter
        return self.application
