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

import logging
import os
from typing import Optional  # noqa: lint doesn't handle inline typehints
from typing import Any, Dict

import yaml
from configuration.exceptions import LoadConfigError

# Location of configs (both service config and mconfig)
CONFIG_DIR = './magma_configs'
CONFIG_OVERRIDE_DIR = './override_configs'
ENB_COMMON_FILE = './magma_configs/acs_common.yml'
ENB_CONFIG_DIR = './magma_configs/serial_number'

def load_override_config(service_name: str) -> Optional[Any]:
    """
    Load override service configuration from the file in the override
    directory.

    Args:
        service_name: service to pull configs for; name of config file

    Returns: json-decoded value of the service config, None if it's not found

    Raises:
        LoadConfigError:
            Unable to load config due to missing file or missing key
    """
    override_file_name = _override_file_name(service_name)
    if os.path.isfile(override_file_name):
        return _load_yaml_file(override_file_name)
    return None


def save_override_config(service_name: str, cfg: Any):
    """
    Write the configuration object to its corresponding file in the override
    directory.

    Args:
        service_name: service to write config object to; name of config file
        cfg: json-decoded value of the service config
    """
    override_file_name = _override_file_name(service_name)
    os.makedirs(CONFIG_OVERRIDE_DIR, exist_ok=True)
    with open(override_file_name, 'w', encoding='utf-8') as override_file:
        yaml.dump(cfg, override_file, default_flow_style=False)


def load_service_config(service_name: str) -> Any:
    """
    Load service configuration from file. Also check override directory,
    and, if service file present there, override the values.

    Args:
        service_name: service to pull configs for; name of config file

    Returns: json-decoded value of the service config

    Raises:
        LoadConfigError:
            Unable to load config due to missing file or missing key
    """
    cfg_file_name = os.path.join(CONFIG_DIR, '%s.yml' % service_name)
    cfg = _load_yaml_file(cfg_file_name)

    overrides = load_override_config(service_name)
    if overrides is not None:
        # Update the keys in the config if they are present in the override
        cfg.update(overrides)
    return cfg

def load_enb_config() -> Any:
    """
    Load the specific serial number enoode configuration as a dictionary

    Args:
        None

    Returns: json-decoded value of the service config
    """

    ret = dict()
    for fname in filter(lambda x: x.endswith(".yml"), os.listdir(ENB_CONFIG_DIR)):
        sn = fname.replace(".yml", "")
        cfg_file_name = os.path.join(ENB_CONFIG_DIR, fname)
        sn_yaml = _load_yaml_file(cfg_file_name)

        enb_cfg = dict()
        for category in sn_yaml.values():
            for key, value in category.items():
                enb_cfg[key] = value

        ret[sn] = enb_cfg

    return ret

def load_common_config() -> Any:
    """
    Load enb common configuration.

    Args:
        None

    Returns: json-decoded value of the service config
    """

    return _load_yaml_file(ENB_COMMON_FILE)


cached_service_configs = {}     # type: Dict[str, Any]


def get_service_config_value(service: str, param: str, default: Any) -> Any:
    """
    Get a config value for :service:, falling back to a :default: value.

    Log error if the default config is returned.

    Args:
        service: name of service to get config for
        param: config key to fetch the value for
        default: default value to return on failure

    Returns:
        value of :param: in the config files for :service:
    """
    service_configs = cached_service_configs.get(service)
    try:
        service_configs = service_configs or load_service_config(service)
    except LoadConfigError as e:
        logging.error('Error retrieving config: %s', e)
        return default

    # Handle empty file
    if not service_configs:
        logging.error('Error retrieving config, file empty for: %s', service)
        return default

    cached_service_configs[service] = service_configs

    config_value = service_configs.get(param)
    if config_value is not None:
        return config_value
    else:
        logging.error(
            'Error retrieving config for %s, key not found: %s',
            service, param,
        )
        return default


def _override_file_name(service_name: str) -> str:
    return os.path.join(CONFIG_OVERRIDE_DIR, '%s.yml' % service_name)


def _load_yaml_file(file_name: str) -> Any:
    """
    Load the yaml file and returns the python object.

    Args:
        file_name: name of the .yml file

    Returns:
        Contents of the yml file deserialized into a Python object

    Raises:
        LoadConfigError: on error
    """

    try:
        with open(file_name, 'r', encoding='utf-8') as stream:
            data = yaml.safe_load(stream)
            return data
    except (OSError, yaml.YAMLError) as e:
        raise LoadConfigError('Error loading yml config') from e