import random


def category_weight(category_id: int | None) -> float:
    """A fake but deterministic-ish stand-in for merchant_categories.risk_weight
    (fraud has no direct DB access -- Redis only, per phase-0-base-project-spec.md §4).
    The business logic does not need to be correct, only to produce a plausible
    spread of scores."""
    if category_id is None:
        return 0.3
    return 0.01 + (category_id % 45) / 44 * 0.94


def score(category_id: int | None, matched: bool) -> float:
    base = category_weight(category_id) * random.uniform(0.05, 0.3)
    if matched:
        return min(1.0, base + random.uniform(0.55, 0.9))
    return min(1.0, base)