# Copyright 2012 OpenStack Foundation
# 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 routes.middleware
import six
import webob.dec
import webob.exc

from keystone.common import config
from keystone.common import dependency
from keystone.common import utils
from keystone import exception
from keystone.openstack.common import gettextutils
from keystone.openstack.common.gettextutils import _
from keystone.openstack.common import importutils
from keystone.openstack.common import jsonutils
from keystone.openstack.common import log


CONF = config.CONF
LOG = log.getLogger(__name__)

# Environment variable used to pass the request context
CONTEXT_ENV = 'openstack.context'


# Environment variable used to pass the request params
PARAMS_ENV = 'openstack.params'


def validate_token_bind(context, token_ref):
    bind_mode = CONF.token.enforce_token_bind

    if bind_mode == 'disabled':
        return

    bind = token_ref.get('bind', {})

    # permissive and strict modes don't require there to be a bind
    permissive = bind_mode in ('permissive', 'strict')

    # get the named mode if bind_mode is not one of the known
    name = None if permissive or bind_mode == 'required' else bind_mode

    if not bind:
        if permissive:
            # no bind provided and none required
            return
        else:
            LOG.info(_("No bind information present in token"))
            raise exception.Unauthorized()

    if name and name not in bind:
        LOG.info(_("Named bind mode %s not in bind information"), name)
        raise exception.Unauthorized()

    for bind_type, identifier in six.iteritems(bind):
        if bind_type == 'kerberos':
            if not (context['environment'].get('AUTH_TYPE', '').lower()
                    == 'negotiate'):
                LOG.info(_("Kerberos credentials required and not present"))
                raise exception.Unauthorized()

            if not context['environment'].get('REMOTE_USER') == identifier:
                LOG.info(_("Kerberos credentials do not match those in bind"))
                raise exception.Unauthorized()

            LOG.info(_("Kerberos bind authentication successful"))

        elif bind_mode == 'permissive':
            LOG.debug(_("Ignoring unknown bind for permissive mode: "
                        "{%(bind_type)s: %(identifier)s}"),
                      {'bind_type': bind_type, 'identifier': identifier})
        else:
            LOG.info(_("Couldn't verify unknown bind: "
                       "{%(bind_type)s: %(identifier)s}"),
                     {'bind_type': bind_type, 'identifier': identifier})
            raise exception.Unauthorized()


def best_match_language(req):
    """Determines the best available locale from the Accept-Language
    HTTP header passed in the request.
    """

    if not req.accept_language:
        return None
    return req.accept_language.best_match(
        gettextutils.get_available_languages('keystone'))


class BaseApplication(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 = keystone.fancy_api:Wadl.factory

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

            import keystone.fancy_api
            keystone.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()
        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 or 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__')


@dependency.requires('assignment_api', 'policy_api', 'token_api')
class Application(BaseApplication):
    @webob.dec.wsgify()
    def __call__(self, req):
        arg_dict = req.environ['wsgiorg.routing_args'][1]
        action = arg_dict.pop('action')
        del arg_dict['controller']
        LOG.debug(_('arg_dict: %s'), arg_dict)

        # allow middleware up the stack to provide context, params and headers.
        context = req.environ.get(CONTEXT_ENV, {})
        context['query_string'] = dict(six.iteritems(req.params))
        context['headers'] = dict(six.iteritems(req.headers))
        context['path'] = req.environ['PATH_INFO']
        context['host_url'] = req.host_url
        params = req.environ.get(PARAMS_ENV, {})
        #authentication and authorization attributes are set as environment
        #values by the container and processed by the pipeline.  the complete
        #set is not yet know.
        context['environment'] = req.environ
        req.environ = None

        params.update(arg_dict)

        context.setdefault('is_admin', False)

        # TODO(termie): do some basic normalization on methods
        method = getattr(self, action)

        # NOTE(vish): make sure we have no unicode keys for py2.6.
        params = self._normalize_dict(params)

        try:
            result = method(context, **params)
        except exception.Unauthorized as e:
            LOG.warning(
                _('Authorization failed. %(exception)s from %(remote_addr)s'),
                {'exception': e, 'remote_addr': req.environ['REMOTE_ADDR']})
            return render_exception(e, context=context,
                                    user_locale=best_match_language(req))
        except exception.Error as e:
            LOG.warning(e)
            return render_exception(e, context=context,
                                    user_locale=best_match_language(req))
        except TypeError as e:
            LOG.exception(e)
            return render_exception(exception.ValidationError(e),
                                    context=context,
                                    user_locale=best_match_language(req))
        except Exception as e:
            LOG.exception(e)
            return render_exception(exception.UnexpectedError(exception=e),
                                    context=context,
                                    user_locale=best_match_language(req))

        if result is None:
            return render_response(status=(204, 'No Content'))
        elif isinstance(result, six.string_types):
            return result
        elif isinstance(result, webob.Response):
            return result
        elif isinstance(result, webob.exc.WSGIHTTPException):
            return result

        response_code = self._get_response_code(req)
        return render_response(body=result, status=response_code)

    def _get_response_code(self, req):
        req_method = req.environ['REQUEST_METHOD']
        controller = importutils.import_class('keystone.common.controller')
        code = None
        if isinstance(self, controller.V3Controller) and req_method == 'POST':
            code = (201, 'Created')
        return code

    def _normalize_arg(self, arg):
        return str(arg).replace(':', '_').replace('-', '_')

    def _normalize_dict(self, d):
        return dict([(self._normalize_arg(k), v)
                     for (k, v) in six.iteritems(d)])

    def assert_admin(self, context):
        if not context['is_admin']:
            try:
                user_token_ref = self.token_api.get_token(context['token_id'])
            except exception.TokenNotFound as e:
                raise exception.Unauthorized(e)

            validate_token_bind(context, user_token_ref)
            creds = user_token_ref['metadata'].copy()

            try:
                creds['user_id'] = user_token_ref['user'].get('id')
            except AttributeError:
                LOG.debug('Invalid user')
                raise exception.Unauthorized()

            try:
                creds['tenant_id'] = user_token_ref['tenant'].get('id')
            except AttributeError:
                LOG.debug('Invalid tenant')
                raise exception.Unauthorized()

            # NOTE(vish): this is pretty inefficient
            creds['roles'] = [self.assignment_api.get_role(role)['name']
                              for role in creds.get('roles', [])]
            # Accept either is_admin or the admin role
            self.policy_api.enforce(creds, 'admin_required', {})

    def _require_attribute(self, ref, attr):
        """Ensures the reference contains the specified attribute."""
        if ref.get(attr) is None or ref.get(attr) == '':
            msg = _('%s field is required and cannot be empty') % attr
            raise exception.ValidationError(message=msg)

    def _get_trust_id_for_request(self, context):
        """Get the trust_id for a call.

        Retrieve the trust_id from the token
        Returns None if token is is not trust scoped
        """
        if ('token_id' not in context or
                context.get('token_id') == CONF.admin_token):
            LOG.debug(_('will not lookup trust as the request auth token is '
                        'either absent or it is the system admin token'))
            return None

        try:
            token_ref = self.token_api.get_token(context['token_id'])
        except exception.TokenNotFound:
            LOG.warning(_('Invalid token in _get_trust_id_for_request'))
            raise exception.Unauthorized()

        return token_ref.get('trust_id')

    @classmethod
    def base_url(cls, context, endpoint_type):
        url = CONF['%s_endpoint' % endpoint_type]

        if url:
            url = url % CONF
        else:
            # NOTE(jamielennox): if url is not set via the config file we
            # should set it relative to the url that the user used to get here
            # so as not to mess with version discovery. This is not perfect.
            # host_url omits the path prefix, but there isn't another good
            # solution that will work for all urls.
            url = context['host_url']

        return url.rstrip('/')


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 = keystone.analytics:Analytics.factory

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

            import keystone.analytics
            keystone.analytics.Analytics(app, 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):
            conf = global_config.copy()
            conf.update(local_config)
            return cls(app, **local_config)
        return _factory

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

    def process_request(self, request):
        """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, request, response):
        """Do whatever you'd like to the response, based on the request."""
        return response

    @webob.dec.wsgify()
    def __call__(self, request):
        try:
            response = self.process_request(request)
            if response:
                return response
            response = request.get_response(self.application)
            return self.process_response(request, response)
        except exception.Error as e:
            LOG.warning(e)
            return render_exception(e, request=request,
                                    user_locale=best_match_language(request))
        except TypeError as e:
            LOG.exception(e)
            return render_exception(exception.ValidationError(e),
                                    request=request,
                                    user_locale=best_match_language(request))
        except Exception as e:
            LOG.exception(e)
            return render_exception(exception.UnexpectedError(exception=e),
                                    request=request,
                                    user_locale=best_match_language(request))


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()
    def __call__(self, req):
        if not hasattr(LOG, 'isEnabledFor') or LOG.isEnabledFor(LOG.debug):
            LOG.debug('%s %s %s', ('*' * 20), 'REQUEST ENVIRON', ('*' * 20))
            for key, value in req.environ.items():
                LOG.debug('%s = %s', key,
                          log.mask_password(value))
            LOG.debug('')
            LOG.debug('%s %s %s', ('*' * 20), 'REQUEST BODY', ('*' * 20))
            for line in req.body_file:
                LOG.debug('%s', log.mask_password(line))
            LOG.debug('')

        resp = req.get_response(self.application)
        if not hasattr(LOG, 'isEnabledFor') or LOG.isEnabledFor(LOG.debug):
            LOG.debug('%s %s %s', ('*' * 20), 'RESPONSE HEADERS', ('*' * 20))
            for (key, value) in six.iteritems(resp.headers):
                LOG.debug('%s = %s', key, value)
            LOG.debug('')

        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."""
        LOG.debug('%s %s %s', ('*' * 20), 'RESPONSE BODY', ('*' * 20))
        for part in app_iter:
            LOG.debug(part)
            yield part


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()
    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()
    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:
            msg = _('The resource could not be found.')
            return render_exception(exception.NotFound(msg),
                                    request=req,
                                    user_locale=best_match_language(req))
        app = match['controller']
        return app


class ComposingRouter(Router):
    def __init__(self, mapper=None, routers=None):
        if mapper is None:
            mapper = routes.Mapper()
        if routers is None:
            routers = []
        for router in routers:
            router.add_routes(mapper)
        super(ComposingRouter, self).__init__(mapper)


class ComposableRouter(Router):
    """Router that supports use by ComposingRouter."""

    def __init__(self, mapper=None):
        if mapper is None:
            mapper = routes.Mapper()
        self.add_routes(mapper)
        super(ComposableRouter, self).__init__(mapper)

    def add_routes(self, mapper):
        """Add routes to given mapper."""
        pass


class ExtensionRouter(Router):
    """A router that allows extensions to supplement or overwrite routes.

    Expects to be subclassed.
    """
    def __init__(self, application, mapper=None):
        if mapper is None:
            mapper = routes.Mapper()
        self.application = application
        self.add_routes(mapper)
        mapper.connect('{path_info:.*}', controller=self.application)
        super(ExtensionRouter, self).__init__(mapper)

    def add_routes(self, mapper):
        pass

    @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 = keystone.analytics:Analytics.factory

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

            import keystone.analytics
            keystone.analytics.Analytics(app, 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):
            conf = global_config.copy()
            conf.update(local_config)
            return cls(app, **local_config)
        return _factory


def render_response(body=None, status=None, headers=None):
    """Forms a WSGI response."""
    headers = headers or []
    headers.append(('Vary', 'X-Auth-Token'))

    if body is None:
        body = ''
        status = status or (204, 'No Content')
    else:
        body = jsonutils.dumps(body, cls=utils.SmarterEncoder)
        headers.append(('Content-Type', 'application/json'))
        status = status or (200, 'OK')

    return webob.Response(body=body,
                          status='%s %s' % status,
                          headerlist=headers)


def render_exception(error, context=None, request=None, user_locale=None):
    """Forms a WSGI response based on the current error."""

    error_message = error.args[0]
    message = gettextutils.translate(error_message, desired_locale=user_locale)
    if message is error_message:
        # translate() didn't do anything because it wasn't a Message,
        # convert to a string.
        message = six.text_type(message)

    body = {'error': {
        'code': error.code,
        'title': error.title,
        'message': message,
    }}
    headers = []
    if isinstance(error, exception.AuthPluginException):
        body['error']['identity'] = error.authentication
    elif isinstance(error, exception.Unauthorized):
        url = CONF.public_endpoint
        if not url:
            if request:
                context = {'host_url': request.host_url}
            if context:
                url = Application.base_url(context, 'public')
            else:
                url = 'http://localhost:%d' % CONF.public_port
        else:
            url = url % CONF

        headers.append(('WWW-Authenticate', 'Keystone uri="%s"' % url))
    return render_response(status=(error.code, error.title),
                           body=body,
                           headers=headers)
