# Copyright 2018 TrilioData Inc.
# All Rights Reserved.

"""RequestContext: context for requests that persist through all of dmapi."""

import copy

from contextlib import contextmanager

from keystoneauth1.access import service_catalog as ksa_service_catalog
from keystoneauth1 import plugin

from oslo_context import context

from oslo_db.sqlalchemy import enginefacade

from oslo_log import log as logging

from oslo_utils import timeutils

import six

from dmapi import exception
from dmapi.i18n import _
from dmapi import policy
from dmapi import utils

LOG = logging.getLogger(__name__)
did_not_respond_sentinel = object()
raised_exception_sentinel = object()


class _ContextAuthPlugin(plugin.BaseAuthPlugin):
    """A keystoneauth auth plugin that uses the values from the Context.

    Ideally we would use the plugin provided by auth_token middleware however
    this plugin isn't serialized yet so we construct one from the serialized
    auth data.
    """

    def __init__(self, auth_token, sc):
        super(_ContextAuthPlugin, self).__init__()

        self.auth_token = auth_token
        self.service_catalog = ksa_service_catalog.ServiceCatalogV2(sc)

    def get_token(self, *args, **kwargs):
        return self.auth_token

    def get_endpoint(self, session, service_type=None, interface=None,
                     region_name=None, service_name=None, **kwargs):
        return self.service_catalog.url_for(service_type=service_type,
                                            service_name=service_name,
                                            interface=interface,
                                            region_name=region_name)


@enginefacade.transaction_context_provider
class RequestContext(context.RequestContext):
    """Security context and request information.

    Represents the user taking a given action within the system.
    """
    def __init__(self, user_id=None, project_id=None, is_admin=None,
                 read_deleted="no", remote_address=None, timestamp=None,
                 quota_class=None, service_catalog=None,
                 instance_lock_checked=False, user_auth_plugin=None, **kwargs):
        """:param read_deleted: 'no' indicates deleted records are hidden,
                'yes' indicates deleted records are visible,
                'only' indicates that *only* deleted records are visible.

           :param overwrite: Set to False to ensure that the greenthread local
                copy of the index is not overwritten.

           :param user_auth_plugin: The auth plugin for the current request's
                authentication data.
        """
        if user_id:
            kwargs['user'] = user_id
        if project_id:
            kwargs['tenant'] = project_id

        super(RequestContext, self).__init__(is_admin=is_admin, **kwargs)

        self.read_deleted = read_deleted
        self.remote_address = remote_address
        if not timestamp:
            timestamp = timeutils.utcnow()
        if isinstance(timestamp, six.string_types):
            timestamp = timeutils.parse_strtime(timestamp)
        self.timestamp = timestamp

        if service_catalog:
            # Only include required parts of service_catalog
            # NOTE(lyarwood): While volumev2 is no longer supported with Queens
            # we still provide it as part of the service catalog as the request
            # context may end up being sent over the wire to a Pike compute
            # that is specifically looking for a cinderv2 type via catalog_info
            self.service_catalog = [s for s in service_catalog
                if s.get('type') in ('image', 'block-storage', 'volumev2',
                                     'volumev3', 'key-manager', 'placement',
                                     'network')]
        else:
            # if list is empty or none
            self.service_catalog = []

        self.instance_lock_checked = instance_lock_checked

        # NOTE(markmc): this attribute is currently only used by the
        # rs_limits turnstile pre-processor.
        # See https://lists.launchpad.net/openstack/msg12200.html
        self.quota_class = quota_class

        self.user_auth_plugin = user_auth_plugin
        if self.is_admin is None:
            self.is_admin = policy.check_is_admin(self)

    def get_auth_plugin(self):
        if self.user_auth_plugin:
            return self.user_auth_plugin
        else:
            return _ContextAuthPlugin(self.auth_token, self.service_catalog)

    def _get_read_deleted(self):
        return self._read_deleted

    def _set_read_deleted(self, read_deleted):
        if read_deleted not in ('no', 'yes', 'only'):
            raise ValueError(_("read_deleted can only be one of 'no', "
                               "'yes' or 'only', not %r") % read_deleted)
        self._read_deleted = read_deleted

    def _del_read_deleted(self):
        del self._read_deleted

    read_deleted = property(_get_read_deleted, _set_read_deleted,
                            _del_read_deleted)

    def to_dict(self):
        values = super(RequestContext, self).to_dict()
        # FIXME(dims): defensive hasattr() checks need to be
        # removed once we figure out why we are seeing stack
        # traces
        values.update({
            'user_id': getattr(self, 'user_id', None),
            'project_id': getattr(self, 'project_id', None),
            'is_admin': getattr(self, 'is_admin', None),
            'read_deleted': getattr(self, 'read_deleted', 'no'),
            'remote_address': getattr(self, 'remote_address', None),
            'timestamp': utils.strtime(self.timestamp) if hasattr(
                self, 'timestamp') else None,
            'request_id': getattr(self, 'request_id', None),
            'quota_class': getattr(self, 'quota_class', None),
            'user_name': getattr(self, 'user_name', None),
            'service_catalog': getattr(self, 'service_catalog', None),
            'project_name': getattr(self, 'project_name', None),
            'instance_lock_checked': getattr(self, 'instance_lock_checked',
                                             False)
        })
        # NOTE(tonyb): This can be removed once we're certain to have a
        # RequestContext contains 'is_admin_project', We can only get away with
        # this because we "know" the default value of 'is_admin_project' which
        # is very fragile.
        values.update({
            'is_admin_project': getattr(self, 'is_admin_project', True),
        })
        return values

    @classmethod
    def from_dict(cls, values):
        return super(RequestContext, cls).from_dict(
            values,
            user_id=values.get('user_id'),
            project_id=values.get('project_id'),
            # TODO(sdague): oslo.context has show_deleted, if
            # possible, we should migrate to that in the future so we
            # don't need to be different here.
            read_deleted=values.get('read_deleted', 'no'),
            remote_address=values.get('remote_address'),
            timestamp=values.get('timestamp'),
            quota_class=values.get('quota_class'),
            service_catalog=values.get('service_catalog'),
            instance_lock_checked=values.get('instance_lock_checked', False),
        )

    def elevated(self, read_deleted=None):
        """Return a version of this context with admin flag set."""
        context = copy.copy(self)
        # context.roles must be deepcopied to leave original roles
        # without changes
        context.roles = copy.deepcopy(self.roles)
        context.is_admin = True

        if 'admin' not in context.roles:
            context.roles.append('admin')

        if read_deleted is not None:
            context.read_deleted = read_deleted

        return context

    def can(self, action, target=None, fatal=True):
        """Verifies that the given action is valid on the target in this context.

        :param action: string representing the action to be checked.
        :param target: dictionary representing the object of the action
            for object creation this should be a dictionary representing the
            location of the object e.g. ``{'project_id': context.project_id}``.
            If None, then this default target will be considered:
            {'project_id': self.project_id, 'user_id': self.user_id}
        :param fatal: if False, will return False when an exception.Forbidden
           occurs.

        :raises dmapi.exception.Forbidden: if verification fails and fatal is
            True.

        :return: returns a non-False value (not necessarily "True") if
            authorized and False if not authorized and fatal is False.
        """
        if target is None:
            target = {'project_id': self.project_id,
                      'user_id': self.user_id}

        try:
            return policy.authorize(self, action, target)
        except exception.Forbidden:
            if fatal:
                raise
            return False

    def to_policy_values(self):
        policy = super(RequestContext, self).to_policy_values()
        policy['is_admin'] = self.is_admin
        return policy

    def __str__(self):
        return "<Context %s>" % self.to_dict()


def get_context():
    """A helper method to get a blank context.

    Note that overwrite is False here so this context will not update the
    greenthread-local stored context that is used when logging.
    """
    return RequestContext(user_id=None,
                          project_id=None,
                          is_admin=False,
                          overwrite=False)


def get_admin_context(read_deleted="no"):
    # NOTE(alaski): This method should only be used when an admin context is
    # necessary for the entirety of the context lifetime. If that's not the
    # case please use get_context(), or create the RequestContext manually, and
    # use context.elevated() where necessary. Some periodic tasks may use
    # get_admin_context so that their database calls are not filtered on
    # project_id.
    return RequestContext(user_id=None,
                          project_id=None,
                          is_admin=True,
                          read_deleted=read_deleted,
                          overwrite=False)


def is_user_context(context):
    """Indicates if the request context is a normal user."""
    if not context:
        return False
    if context.is_admin:
        return False
    if not context.user_id or not context.project_id:
        return False
    return True


def require_context(ctxt):
    """Raise exception.Forbidden() if context is not a user or an
    admin context.
    """
    if not ctxt.is_admin and not is_user_context(ctxt):
        raise exception.Forbidden()


def authorize_project_context(context, project_id):
    """Ensures a request has permission to access the given project."""
    if is_user_context(context):
        if not context.project_id:
            raise exception.Forbidden()
        elif context.project_id != project_id:
            raise exception.Forbidden()


def authorize_user_context(context, user_id):
    """Ensures a request has permission to access the given user."""
    if is_user_context(context):
        if not context.user_id:
            raise exception.Forbidden()
        elif context.user_id != user_id:
            raise exception.Forbidden()


def authorize_quota_class_context(context, class_name):
    """Ensures a request has permission to access the given quota class."""
    if is_user_context(context):
        if not context.quota_class:
            raise exception.Forbidden()
        elif context.quota_class != class_name:
            raise exception.Forbidden()


CELL_CACHE = {}
def set_target_cell(context, cell_mapping):
    """Adds database connection information to the context
    for communicating with the given target_cell.

    This is used for permanently targeting a cell in a context.
    Use this when you want all subsequent code to target a cell.

    Passing None for cell_mapping will untarget the context.

    :param context: The RequestContext to add connection information
    :param cell_mapping: An objects.CellMapping object or None
    """
    global CELL_CACHE
    if cell_mapping is not None:
        # avoid circular import
        from dmapi import db
        from dmapi import rpc

        # Synchronize access to the cache by multiple API workers.
        @utils.synchronized(cell_mapping.uuid)
        def get_or_set_cached_cell_and_set_connections():
            try:
                cell_tuple = CELL_CACHE[cell_mapping.uuid]
            except KeyError:
                db_connection_string = cell_mapping.database_connection
                context.db_connection = db.create_context_manager(
                    db_connection_string)
                if not cell_mapping.transport_url.startswith('none'):
                    context.mq_connection = rpc.create_transport(
                        cell_mapping.transport_url)
                CELL_CACHE[cell_mapping.uuid] = (context.db_connection,
                                                 context.mq_connection)
            else:
                context.db_connection = cell_tuple[0]
                context.mq_connection = cell_tuple[1]

        get_or_set_cached_cell_and_set_connections()
    else:
        context.db_connection = None
        context.mq_connection = None


@contextmanager
def target_cell(context, cell_mapping):
    """Yields a new context with connection information for a specific cell.

    This function yields a copy of the provided context, which is targeted to
    the referenced cell for MQ and DB connections.

    Passing None for cell_mapping will yield an untargetd copy of the context.

    :param context: The RequestContext to add connection information
    :param cell_mapping: An objects.CellMapping object or None
    """
    # Create a sanitized copy of context by serializing and deserializing it
    # (like we would do over RPC). This help ensure that we have a clean
    # copy of the context with all the tracked attributes, but without any
    # of the hidden/private things we cache on a context. We do this to avoid
    # unintentional sharing of cached thread-local data across threads.
    # Specifically, this won't include any oslo_db-set transaction context, or
    # any existing cell targeting.
    cctxt = RequestContext.from_dict(context.to_dict())
    set_target_cell(cctxt, cell_mapping)
    yield cctxt