"""Golden tests for TRANSITION_SET_ENUMERATOR_V1 (governance/todo/v8_9_p2_adoption_plan.yaml P2-B).

Maps to v8.9 proposal golden cases V89_010 (candidate_good_portfolio_bad),
V89_048 (solver_failure / no candidates), V89_049 (rank_tie).
"""
from __future__ import annotations

import importlib.util
from pathlib import Path

ROOT = Path(__file__).resolve().parents[3]
MODULE_PATH = ROOT / "tools" / "build_transition_set_enumerator_v1.py"


def _load_module():
    spec = importlib.util.spec_from_file_location("build_transition_set_enumerator_v1", MODULE_PATH)
    module = importlib.util.module_from_spec(spec)
    assert spec.loader is not None
    spec.loader.exec_module(module)
    return module


def test_v89_010_individually_passing_combo_rejected_when_jointly_breaching_cash_floor() -> None:
    mod = _load_module()
    candidates = [
        {
            "candidate_id": "A",
            "hard_constraint_pass": True,
            "transition_utility_krw": 100000,
            "post_trade_cash_floor_delta_pct": 1.0,
            "post_trade_concentration_delta_pct": 0.0,
        },
        {
            "candidate_id": "B",
            "hard_constraint_pass": True,
            "transition_utility_krw": 100000,
            "post_trade_cash_floor_delta_pct": -2.0,
            "post_trade_concentration_delta_pct": 0.0,
        },
    ]
    evaluated = mod.enumerate_transition_sets(candidates, max_set_size=2)
    combo_ab = next(s for s in evaluated if set(s["candidate_ids"]) == {"A", "B"})
    assert combo_ab["set_hard_constraint_pass"] is False

    best = mod.select_best_set(evaluated)
    assert best["candidate_ids"] == ["A"]


def test_v89_048_no_candidates_yields_empty_set_not_fabricated() -> None:
    mod = _load_module()
    evaluated = mod.enumerate_transition_sets([], max_set_size=3)
    assert evaluated == []
    assert mod.select_best_set(evaluated) is None


def test_v89_049_tie_prefers_smaller_lower_complexity_combination() -> None:
    mod = _load_module()
    sets = [
        {"candidate_ids": ["A"], "set_hard_constraint_pass": True, "set_transition_utility_krw": 100000.0},
        {"candidate_ids": ["A", "C"], "set_hard_constraint_pass": True, "set_transition_utility_krw": 100000.0},
    ]
    best = mod.select_best_set(sets)
    assert best["candidate_ids"] == ["A"]