# Copyright 2014
# The Cloudscaling Group, 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.

from xml.sax import saxutils

from oslo.config import cfg
import webob.dec
import webob.exc

import ec2api.api
from ec2api import context
from ec2api.openstack.common import gettextutils
from ec2api.openstack.common import log as logging

CONF = cfg.CONF
LOG = logging.getLogger(__name__)


def xhtml_escape(value):
    """Escapes a string so it is valid within XML or XHTML.

    """
    return saxutils.escape(value, {'"': '"', "'": '''})


def utf8(value):
    """Try to turn a string into utf-8 if possible.

    Code is directly from the utf8 function in
    http://github.com/facebook/tornado/blob/master/tornado/escape.py

    """
    if isinstance(value, unicode):
        return value.encode('utf-8')
    elif isinstance(value, gettextutils.Message):
        return unicode(value).encode('utf-8')
    assert isinstance(value, str)
    return value


def ec2_error_response(request_id, code, message, status=500):
    """Helper to construct an EC2 compatible error response."""
    LOG.debug('EC2 error response: %(code)s: %(message)s',
              {'code': code, 'message': message})
    resp = webob.Response()
    resp.status = status
    resp.headers['Content-Type'] = 'text/xml'
    resp.body = str('<?xml version="1.0"?>\n'
                    '<Response><Errors><Error><Code>%s</Code>'
                    '<Message>%s</Message></Error></Errors>'
                    '<RequestID>%s</RequestID></Response>' %
                    (xhtml_escape(utf8(code)),
                     xhtml_escape(utf8(message)),
                     xhtml_escape(utf8(request_id))))
    return resp


class Fault(webob.exc.HTTPException):

    """Captures exception and return REST Response."""

    def __init__(self, exception):
        """Create a response for the given webob.exc.exception."""
        self.wrapped_exc = exception

    @webob.dec.wsgify
    def __call__(self, req):
        """Generate a WSGI response based on the exception passed to ctor."""
        code = ec2api.api.exception_to_ec2code(self.wrapped_exc)
        status = self.wrapped_exc.status_int
        message = self.wrapped_exc.explanation

        if status == 501:
            message = "The requested function is not supported"

        if 'AWSAccessKeyId' not in req.params:
            raise webob.exc.HTTPBadRequest()
        user_id, _sep, project_id = req.params['AWSAccessKeyId'].partition(':')
        project_id = project_id or user_id
        remote_address = getattr(req, 'remote_address', '127.0.0.1')
        if CONF.use_forwarded_for:
            remote_address = req.headers.get('X-Forwarded-For', remote_address)

        resp = ec2_error_response(context.generate_request_id(), code,
                                  message=message, status=status)
        return resp