# -*- coding: utf-8 -*-
import os
import json
from abc import ABCMeta, abstractmethod

DEFAULT_METADATA_DIR = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "metadata"))

class BaseFetcher(object):
    __metaclass__ = ABCMeta

    def __init__(self, provider_name, metadata_dir=None):
        if self.__class__ is BaseFetcher:
            raise TypeError("Cannot instantiate abstract class BaseFetcher directly")
        self.provider_name = provider_name
        self.metadata_dir = metadata_dir or DEFAULT_METADATA_DIR
        self.metadata = self._load_metadata()

    def _load_metadata(self):
        file_path = os.path.join(self.metadata_dir, "{}_meta.json".format(self.provider_name))
        if not os.path.exists(file_path):
            return {}
        try:
            with open(file_path, "r") as f:
                return json.load(f)
        except Exception:
            return {}

    def fetch_external_vac_info(self, origin, target, visa_type, vac_code=None):
        """
        Hook for retrieving VAC information online from external tools/APIs when not found in metadata.
        """
        return None

    @abstractmethod
    def fetch_free_config(self, origin, target, visa_type, vac_code=None):
        pass