# SPDX-FileCopyrightText: 2020 The Magma Authors.
# SPDX-FileCopyrightText: 2022 Open Networking Foundation <support@opennetworking.org>
#
# SPDX-License-Identifier: BSD-3-Clause

import json
import logging
from contextlib import closing
from typing import Any, Dict

import pkg_resources
import yaml
from bravado_core.spec import Spec
from bravado_core.validate import validate_object as bravado_validate

EVENT_REGISTRY = 'event_registry'
SWAGGER_SPEC = 'swagger_spec'
BRAVADO_SPEC = 'bravado_spec'
MODULE = 'module'
FILENAME = 'filename'
DEFINITIONS = 'definitions'


class EventValidator(object):
    """
    gRPC based server for EventD.
    """

    def __init__(self, config: Dict[str, Any]):
        self.event_registry = config[EVENT_REGISTRY]
        self.specs_by_filename = self._load_specs_from_registry()

    def validate_event(self, raw_event: str, event_type: str) -> None:
        """
        Checks if an event is registered and validates it based on
        a registered schema.
        Args:
            raw_event: The event to be validated, as a JSON-encoded string
            event_type: The type of an event, which corresponds
            to a generated model
        Returns:
            Does not return, but throws exceptions if validation fails.
        """
        event = json.loads(raw_event)

        # Event not in registry
        if event_type not in self.event_registry:
            logging.debug(
                'Event type %s not among registered event types (%s)',
                event_type, self.event_registry,
            )
            raise KeyError(
                'Event type {} not registered, '
                'please add it to the EventD config'.format(event_type),
            )
        filename = self.event_registry[event_type][FILENAME]
        bravado_validate(
            self.specs_by_filename[filename][BRAVADO_SPEC],
            self.specs_by_filename[filename][SWAGGER_SPEC][event_type],
            event,
        )

    def _load_specs_from_registry(self) -> Dict[str, Any]:
        """
        Loads all swagger definitions from the files specified in the
        event registry.
        """
        specs_by_filename = {}
        for event_type, info in self.event_registry.items():
            filename = info[FILENAME]
            if filename in specs_by_filename:
                # Spec for this file is already registered
                self._check_event_exists_in_spec(
                    specs_by_filename[filename][SWAGGER_SPEC],
                    filename,
                    event_type,
                )
                continue

            module = '{}.swagger.specs'.format(info[MODULE])
            if not pkg_resources.resource_exists(module, filename):
                raise LookupError(
                    'File {} not found under {}/swagger, please ensure that '
                    'it exists'.format(filename, info[MODULE]),
                )

            stream = pkg_resources.resource_stream(module, filename)
            with closing(stream) as spec_file:
                swagger_spec = yaml.safe_load(spec_file)
                self._check_event_exists_in_spec(
                    swagger_spec[DEFINITIONS], filename, event_type,
                )

                config = {'validate_swagger_spec': False}
                bravado_spec = Spec.from_dict(swagger_spec, config=config)
                specs_by_filename[filename] = {
                    SWAGGER_SPEC: swagger_spec[DEFINITIONS],
                    BRAVADO_SPEC: bravado_spec,
                }

        return specs_by_filename

    @staticmethod
    def _check_event_exists_in_spec(
            swagger_definitions: Dict[str, Any],
            filename: str,
            event_type: str,
    ):
        """
        Throw a KeyError if the event_type does not exist in swagger_definitions
        """
        if event_type not in swagger_definitions:
            raise KeyError(
                'Event type {} is not defined in {}, '
                'please add the definition and re-generate '
                'swagger specifications'.format(event_type, filename),
            )