from reactor_sim.atomic import AtomicPhysics
from reactor_sim.fuel import FuelAssembly
from reactor_sim.state import CoreState


def _core_state(
    temp: float = 600.0,
    flux: float = 1e6,
    burnup: float = 0.05,
    power: float = 100.0,
) -> CoreState:
    return CoreState(
        fuel_temperature=temp,
        neutron_flux=flux,
        reactivity_margin=0.0,
        power_output_mw=power,
        burnup=burnup,
    )


def test_decay_reaction_power_positive_and_capped():
    physics = AtomicPhysics(seed=7)
    fuel = FuelAssembly(enrichment=0.045, mass_kg=80_000.0, atomic_physics=physics)
    state = _core_state()
    power = fuel.decay_reaction_power(state)
    assert power > 0
    # Should stay under 10% of current power_output_mw.
    assert power <= state.power_output_mw * 0.1 + 1e-6


def test_decay_reaction_power_scales_with_burnup_and_flux():
    physics = AtomicPhysics(seed=9)
    fuel = FuelAssembly(enrichment=0.045, mass_kg=80_000.0, atomic_physics=physics)
    low = _core_state(burnup=0.01, flux=1e5, power=50.0)
    high = _core_state(burnup=0.5, flux=5e6, power=200.0)
    low_power = fuel.decay_reaction_power(low)
    high_power = fuel.decay_reaction_power(high)
    assert high_power > low_power
    # Still capped to a reasonable fraction of the prevailing power.
    assert high_power <= high.power_output_mw * 0.1 + 1e-6