"""
Module that define classes to convert Crypto-currency to FIAT
e.g BTC to USD
"""

import datetime
import logging
from typing import Dict, List

from cachetools.ttl import TTLCache
from pycoingecko import CoinGeckoAPI
from requests.exceptions import RequestException

from freqtrade.constants import SUPPORTED_FIAT


logger = logging.getLogger(__name__)


class CryptoToFiatConverter:
    """
    Main class to initiate Crypto to FIAT.
    This object contains a list of pair Crypto, FIAT
    This object is also a Singleton
    """
    __instance = None
    _coingekko: CoinGeckoAPI = None
    _coinlistings: List[Dict] = []
    _backoff: float = 0.0

    def __new__(cls):
        """
        This class is a singleton - cannot be instantiated twice.
        """
        if CryptoToFiatConverter.__instance is None:
            CryptoToFiatConverter.__instance = object.__new__(cls)
            try:
                CryptoToFiatConverter._coingekko = CoinGeckoAPI()
            except BaseException:
                CryptoToFiatConverter._coingekko = None
        return CryptoToFiatConverter.__instance

    def __init__(self) -> None:
        # Timeout: 6h
        self._pair_price: TTLCache = TTLCache(maxsize=500, ttl=6 * 60 * 60)

        self._load_cryptomap()

    def _load_cryptomap(self) -> None:
        try:
            # Use list-comprehension to ensure we get a list.
            self._coinlistings = [x for x in self._coingekko.get_coins_list()]
        except RequestException as request_exception:
            if "429" in str(request_exception):
                logger.warning(
                    "Too many requests for Coingecko API, backing off and trying again later.")
                # Set backoff timestamp to 60 seconds in the future
                self._backoff = datetime.datetime.now().timestamp() + 60
                return
            # If the request is not a 429 error we want to raise the normal error
            logger.error(
                "Could not load FIAT Cryptocurrency map for the following problem: {}".format(
                    request_exception
                )
            )
        except (Exception) as exception:
            logger.error(
                f"Could not load FIAT Cryptocurrency map for the following problem: {exception}")

    def _get_gekko_id(self, crypto_symbol):
        if not self._coinlistings:
            if self._backoff <= datetime.datetime.now().timestamp():
                self._load_cryptomap()
                # Still not loaded.
                if not self._coinlistings:
                    return None
            else:
                return None
        found = [x for x in self._coinlistings if x['symbol'] == crypto_symbol]
        if len(found) == 1:
            return found[0]['id']

        if len(found) > 0:
            # Wrong!
            logger.warning(f"Found multiple mappings in goingekko for {crypto_symbol}.")
            return None

    def convert_amount(self, crypto_amount: float, crypto_symbol: str, fiat_symbol: str) -> float:
        """
        Convert an amount of crypto-currency to fiat
        :param crypto_amount: amount of crypto-currency to convert
        :param crypto_symbol: crypto-currency used
        :param fiat_symbol: fiat to convert to
        :return: float, value in fiat of the crypto-currency amount
        """
        if crypto_symbol == fiat_symbol:
            return float(crypto_amount)
        price = self.get_price(crypto_symbol=crypto_symbol, fiat_symbol=fiat_symbol)
        return float(crypto_amount) * float(price)

    def get_price(self, crypto_symbol: str, fiat_symbol: str) -> float:
        """
        Return the price of the Crypto-currency in Fiat
        :param crypto_symbol: Crypto-currency you want to convert (e.g BTC)
        :param fiat_symbol: FIAT currency you want to convert to (e.g USD)
        :return: Price in FIAT
        """
        crypto_symbol = crypto_symbol.lower()
        fiat_symbol = fiat_symbol.lower()
        inverse = False

        if crypto_symbol == 'usd':
            # usd corresponds to "uniswap-state-dollar" for coingecko.
            # We'll therefore need to "swap" the currencies
            logger.info(f"reversing Rates {crypto_symbol}, {fiat_symbol}")
            crypto_symbol = fiat_symbol
            fiat_symbol = 'usd'
            inverse = True

        symbol = f"{crypto_symbol}/{fiat_symbol}"
        # Check if the fiat conversion you want is supported
        if not self._is_supported_fiat(fiat=fiat_symbol):
            raise ValueError(f'The fiat {fiat_symbol} is not supported.')

        price = self._pair_price.get(symbol, None)

        if not price:
            price = self._find_price(
                crypto_symbol=crypto_symbol,
                fiat_symbol=fiat_symbol
            )
            if inverse and price != 0.0:
                price = 1 / price
            self._pair_price[symbol] = price

        return price

    def _is_supported_fiat(self, fiat: str) -> bool:
        """
        Check if the FIAT your want to convert to is supported
        :param fiat: FIAT to check (e.g USD)
        :return: bool, True supported, False not supported
        """

        return fiat.upper() in SUPPORTED_FIAT

    def _find_price(self, crypto_symbol: str, fiat_symbol: str) -> float:
        """
        Call CoinGekko API to retrieve the price in the FIAT
        :param crypto_symbol: Crypto-currency you want to convert (e.g btc)
        :param fiat_symbol: FIAT currency you want to convert to (e.g usd)
        :return: float, price of the crypto-currency in Fiat
        """
        # Check if the fiat conversion you want is supported
        if not self._is_supported_fiat(fiat=fiat_symbol):
            raise ValueError(f'The fiat {fiat_symbol} is not supported.')

        # No need to convert if both crypto and fiat are the same
        if crypto_symbol == fiat_symbol:
            return 1.0

        _gekko_id = self._get_gekko_id(crypto_symbol)

        if not _gekko_id:
            # return 0 for unsupported stake currencies (fiat-convert should not break the bot)
            logger.warning("unsupported crypto-symbol %s - returning 0.0", crypto_symbol)
            return 0.0

        try:
            return float(
                self._coingekko.get_price(
                    ids=_gekko_id,
                    vs_currencies=fiat_symbol
                )[_gekko_id][fiat_symbol]
            )
        except Exception as exception:
            logger.error("Error in _find_price: %s", exception)
            return 0.0