"""Golden tests for FORECAST_SIMULATION_ENGINE_V1 (governance/todo/v8_9_p0_adoption_plan.yaml P0-3.3).

Maps to v8.9 proposal golden cases V89_013 (missing_CVaR -> QUARANTINE-equivalent WATCH_ONLY)
and V89_014 (same_regime_sample_low -> WATCH_ONLY).
"""
from __future__ import annotations

import importlib.util
import json
from pathlib import Path

ROOT = Path(__file__).resolve().parents[3]
MODULE_PATH = ROOT / "tools" / "build_forecast_simulation_engine_v1.py"


def _load_module():
    spec = importlib.util.spec_from_file_location("build_forecast_simulation_engine_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_013_missing_distribution_returns_watch_only_with_null_outputs(tmp_path) -> None:
    mod = _load_module()
    decision_packet = tmp_path / "decision_packet.json"
    decision_packet.write_text(json.dumps({"execution_mode": "SHADOW"}), encoding="utf-8")
    out = tmp_path / "out.json"

    import sys

    sys.argv = [
        "build_forecast_simulation_engine_v1.py",
        "--backtest-contract", str(tmp_path / "missing_contract.yaml"),
        "--distribution", str(tmp_path / "missing_distribution.json"),
        "--decision-packet", str(decision_packet),
        "--out", str(out),
    ]
    assert mod.main() == 0
    result = json.loads(out.read_text(encoding="utf-8"))
    assert result["gate"] == "WATCH_ONLY"
    assert result["ce70_net_profit_krw"] is None
    assert result["cvar95_loss_krw"] is None


def test_v89_014_same_regime_sample_below_shadow_minimum_blocks_compute() -> None:
    mod = _load_module()
    rule = mod.MINIMUM_SAMPLE_RULES["SHADOW"]
    sample_count_total = 30
    sample_count_same_regime = 5
    gate_ok = (
        sample_count_total >= rule["sample_count_total_min"]
        and sample_count_same_regime >= rule["sample_count_same_regime_min"]
    )
    assert gate_ok is False


def test_quantile_and_cvar95_match_known_distribution() -> None:
    mod = _load_module()
    values = sorted(float(v) for v in range(1, 101))
    assert mod._quantile(values, 0.5) == 50.5
    assert mod._cvar95(values) <= values[4]