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"""Module defining RefineHiStrategy class."""


from dataclasses import dataclass
from typing import Optional, Tuple

from ..discrete_load import DiscreteLoad
from ..discrete_width import DiscreteWidth
from ..relevant_bounds import RelevantBounds
from .base import StrategyBase


@dataclass
class RefineHiStrategy(StrategyBase):
    """If initial upper bound is still worth it, nominate it.

    This usually happens when halving resulted in relevant lower bound,
    or if there was no halving (and RefineLoStrategy confirmed initial
    lower bound became a relevant lower bound for the new current target).

    This either ensures a matching upper bound (target is achieved)
    or moves the relevant lower bound higher (triggering external search).
    """

    def nominate(
        self, bounds: RelevantBounds
    ) -> Tuple[Optional[DiscreteLoad], Optional[DiscreteWidth]]:
        """Nominate the initial upper bound.

        :param bounds: Freshly updated bounds relevant for current target.
        :type bounds: RelevantBounds
        :returns: Two nones or candidate intended load and duration.
        :rtype: Tuple[Optional[DiscreteLoad], Optional[DiscreteWidth]]
        """
        if not (load := self.initial_upper_load):
            return None, None
        if self.not_worth(bounds=bounds, load=load):
            return None, None
        self.debug(f"Upperbound refinement available: {load}")
        # TODO: Limit to possibly smaller than target width?
        self.expander.limit(self.target.discrete_width)
        return load, self.target.discrete_width