"""Static Currency data."""

import os

import pkg_resources

from abacus_common_data.xml_parse import yield_currencies

CURRENT_ISO_FILE = pkg_resources.resource_filename(
    'abacus_common_data', 'data/xml/current_iso_currencies.xml')
CURRENT_ISO_PATH = 'CcyTbl/CcyNtry'
HISTORICAL_ISO_FILE = pkg_resources.resource_filename(
    'abacus_common_data', 'data/xml/historical_iso_currencies.xml')
HISTORICAL_ISO_PATH = 'HstrcCcyTbl/HstrcCcyNtry'


class Currency:
    """Currency class."""

    currency_map = {}

    def __init__(self, code):
        """Find currency by code. Raises KeyError on unknown code."""
        Currency._load_xml_data()
        self.currency = Currency._get_iso_data(code)

    @staticmethod
    def parse_iso_xml(file_path, xml_path):
        """Build a keyed dict of currency code data."""
        currency_map = {}
        for child in yield_currencies(file_path, xml_path):
            code = child.get('currency_code')
            currency_map[code] = child
        return currency_map

    @classmethod
    def _get_iso_data(cls, code):
        """Force a key error if not found."""
        return cls.currency_map[code]

    @classmethod
    def _load_xml_data(cls):
        """Initialize the class, loading data in from ISO xml files."""
        if cls.currency_map:
            return
        cls.currency_map = Currency.parse_iso_xml(
            CURRENT_ISO_FILE, CURRENT_ISO_PATH)
        historical_iso_codes = Currency.parse_iso_xml(
            HISTORICAL_ISO_FILE, HISTORICAL_ISO_PATH)
        for historical_code in cls._get_user_params():
            cls.currency_map[historical_code] = \
                historical_iso_codes[historical_code]

    @classmethod
    def _get_user_params(cls):
        """Return an array of user supplied historical codes to honor.

        Format should be comma-delimited without spaces.

        """
        user_params = os.environ.get(
            'HISTORICAL_ISO_CODES',
            # Default list of supported historical ISO codes.
            'BYR,EEK,LTL,LVL,MRO,SKK,STD,TMM,VEF,ZWD'
        ).split(',')
        return list(filter(None, user_params))

    @property
    def code(self):
        """Currency ISO-4217 code."""
        return self.currency.get('currency_code')

    @property
    def number(self):
        """Currency ISO-4217 number."""
        return self.currency.get('currency_number')

    @property
    def currency_name(self):
        """Currency ISO-4217 name."""
        return self.currency.get('currency_name')


def get_currency_object_from_code(currency_code):
    """Return an object formatted like the legacy currency schema."""
    currency = Currency(currency_code)
    return {
        'currency_id': currency.number,
        'currency_code': currency.code,
        'currency_name': currency.currency_name
    }