"""DDI safety rules."""

from __future__ import annotations

_CONTRAINDICATED: set[tuple[str, str]] = {
    ("warfarin_like", "nsaid_like"),
    ("benzodiazepine_like", "opioid_like"),
}


def is_contraindicated_pair(drug_a: str, drug_b: str) -> bool:
    key = tuple(sorted((drug_a, drug_b)))
    canon = {tuple(sorted(item)) for item in _CONTRAINDICATED}
    return key in canon


def top_risky_pairs(drugs: list[str]) -> list[tuple[str, str]]:
    hits: list[tuple[str, str]] = []
    for i, a in enumerate(drugs):
        for b in drugs[i + 1 :]:
            if is_contraindicated_pair(a, b):
                hits.append((a, b))
    return hits