import json
from pathlib import Path

import pytest

from reactor_sim import constants
from reactor_sim.reactor import Reactor
from reactor_sim.simulation import ReactorSimulation


def test_reactor_initial_state_is_cold():
    reactor = Reactor.default()
    state = reactor.initial_state()
    assert state.core.fuel_temperature == constants.ENVIRONMENT_TEMPERATURE
    assert state.primary_loop.mass_flow_rate == 0.0
    assert state.turbine.electrical_output_mw == 0.0


def test_state_save_and_load_roundtrip(tmp_path: Path):
    reactor = Reactor.default()
    sim = ReactorSimulation(reactor, timestep=5.0, duration=15.0)
    sim.log()
    save_path = tmp_path / "plant_state.json"
    assert sim.last_state is not None
    reactor.save_state(str(save_path), sim.last_state)
    assert save_path.exists()
    restored_reactor = Reactor.default()
    restored_state = restored_reactor.load_state(str(save_path))
    assert restored_state.core.fuel_temperature == pytest.approx(
        sim.last_state.core.fuel_temperature
    )
    assert restored_reactor.control.rod_fraction == reactor.control.rod_fraction


def test_health_monitor_flags_core_failure():
    reactor = Reactor.default()
    state = reactor.initial_state()
    state.core.fuel_temperature = constants.MAX_CORE_TEMPERATURE
    failures = reactor.health_monitor.evaluate(state, True, True, True, dt=200.0)
    assert "core" in failures
    reactor._handle_failure("core")
    assert reactor.shutdown is True