import random

from .data import small_final_calculation
from .envs import Pool, make_episode


class SmallCalculationPool(Pool):
    fraction: float = .8

    def __init__(self, rows: list[dict]):
        if not 0 <= self.fraction <= 1:
            raise ValueError('Small-calculation sampling fraction must be in [0, 1]')
        super().__init__(rows)
        small = {row['group'] for row in rows
                 if small_final_calculation(dict(steps=row['provenance']['equations']))}
        self.small_by_hint = {level: [row for row in selected if row['group'] in small]
                              for level, selected in self.by_hint.items()}

    def sample(self, rng: random.Random):
        level = rng.randint(1, 16)
        if self.small_by_hint[level] and rng.random() < self.fraction:
            row = rng.choice(self.small_by_hint[level])
        else:
            bands = list(self.by_band[level])
            band = rng.choices(bands, [self.weights[name] for name in bands])[0]
            row = rng.choice(self.by_band[level][band])
        return make_episode(row, level)