import configparser
import logging
import sys
import os

from ucloud.common.etcd_wrapper import Etcd3Wrapper


logger = logging.getLogger(__name__)


class CustomConfigParser(configparser.RawConfigParser):
    def __getitem__(self, key):
        try:
            result = super().__getitem__(key)
        except KeyError as err:
            raise KeyError("Key '{}' not found in config file"\
                           .format(key)) from err
        else:
            return result


class Settings(object):
    def __init__(self, config_key='/uncloud/config/'):
        conf_name = 'ucloud.conf'
        conf_dir = os.environ.get('UCLOUD_CONF_DIR', '/etc/ucloud')
        config_file = os.path.join(conf_dir, conf_name)
        
        self.config_parser = CustomConfigParser(allow_no_value=True)
        self.config_key = config_key

        self.read_internal_values()
        self.read_config_file_values(config_file)

        self.etcd_wrapper_args = tuple()
        self.etcd_wrapper_kwargs = {
            'host':      self.config_parser['etcd']['url'],
            'port':      self.config_parser['etcd']['port'],
            'ca_cert':   self.config_parser['etcd']['ca_cert'],
            'cert_cert': self.config_parser['etcd']['cert_cert'],
            'cert_key':  self.config_parser['etcd']['cert_key']
        }

    
    def get_etcd_client(self):
        args = self.etcd_wrapper_args
        kwargs = self.etcd_wrapper_kwargs
        return Etcd3Wrapper(*args, **kwargs)
        
    def read_internal_values(self):
        self.config_parser.read_dict({
            'etcd': {
                'file_prefix': '/files/',
                'host_prefix': '/hosts/',
                'image_prefix': '/images/',
                'image_store_prefix': '/imagestore/',
                'network_prefix': '/networks/',
                'request_prefix': '/requests/',
                'user_prefix': '/users/',
                'vm_prefix': '/vms/',
            }
        })

    def read_config_file_values(self, config_file):
        try:
            # Trying to read configuration file
            with open(config_file, "r") as config_file_handle:
                self.config_parser.read_file(config_file_handle)
        except FileNotFoundError:
            sys.exit('Configuration file {} not found!'.format(config_file))
        except Exception as err:
            logger.exception(err)
            sys.exit("Error occurred while reading configuration file")

    def read_values_from_etcd(self):
        etcd_client = self.get_etcd_client()
        config_from_etcd = etcd_client.get(self.config_key, value_in_json=True)
        if config_from_etcd:
            self.config_parser.read_dict(config_from_etcd.value)
        else:
            return
            sys.exit("No settings found in etcd at key {}".format(self.config_key))
    
    def __getitem__(self, key):
        self.read_values_from_etcd()
        return self.config_parser[key]