"""
Offset pair list filter
"""
import logging
from typing import Any, Dict, List

from freqtrade.constants import Config
from freqtrade.exceptions import OperationalException
from freqtrade.exchange.types import Tickers
from freqtrade.plugins.pairlist.IPairList import IPairList, PairlistParameter


logger = logging.getLogger(__name__)


class OffsetFilter(IPairList):

    def __init__(self, exchange, pairlistmanager,
                 config: Config, pairlistconfig: Dict[str, Any],
                 pairlist_pos: int) -> None:
        super().__init__(exchange, pairlistmanager, config, pairlistconfig, pairlist_pos)

        self._offset = pairlistconfig.get('offset', 0)
        self._number_pairs = pairlistconfig.get('number_assets', 0)

        if self._offset < 0:
            raise OperationalException("OffsetFilter requires offset to be >= 0")

    @property
    def needstickers(self) -> bool:
        """
        Boolean property defining if tickers are necessary.
        If no Pairlist requires tickers, an empty Dict is passed
        as tickers argument to filter_pairlist
        """
        return False

    def short_desc(self) -> str:
        """
        Short whitelist method description - used for startup-messages
        """
        if self._number_pairs:
            return f"{self.name} - Taking {self._number_pairs} Pairs, starting from {self._offset}."
        return f"{self.name} - Offsetting pairs by {self._offset}."

    @staticmethod
    def description() -> str:
        return "Offset pair list filter."

    @staticmethod
    def available_parameters() -> Dict[str, PairlistParameter]:
        return {
            "offset": {
                "type": "number",
                "default": 0,
                "description": "Offset",
                "help": "Offset of the pairlist.",
            },
            "number_assets": {
                "type": "number",
                "default": 0,
                "description": "Number of assets",
                "help": "Number of assets to use from the pairlist, starting from offset.",
            },
        }

    def filter_pairlist(self, pairlist: List[str], tickers: Tickers) -> List[str]:
        """
        Filters and sorts pairlist and returns the whitelist again.
        Called on each bot iteration - please use internal caching if necessary
        :param pairlist: pairlist to filter or sort
        :param tickers: Tickers (from exchange.get_tickers). May be cached.
        :return: new whitelist
        """
        if self._offset > len(pairlist):
            self.log_once(f"Offset of {self._offset} is larger than " +
                          f"pair count of {len(pairlist)}", logger.warning)
        pairs = pairlist[self._offset:]
        if self._number_pairs:
            pairs = pairs[:self._number_pairs]

        self.log_once(f"Searching {len(pairs)} pairs: {pairs}", logger.info)

        return pairs
