"""Real config loading and pure structural update for the frozen development case."""
import importlib.util
import math
from pathlib import Path

import numpy as np
import pytest

path = Path(__file__).resolve().parents[2] / 'research/steady_pinball/run.py'
spec = importlib.util.spec_from_file_location('steady_pinball_run', path)
runner = importlib.util.module_from_spec(spec)
spec.loader.exec_module(runner)


def test_actual_loader_and_paper_geometry(tmp_path):
    import json
    from CelerisLab.config import load_lbm_config
    p = tmp_path/'config.json'
    p.write_text(json.dumps(runner.config()))
    cfg = load_lbm_config(str(p))
    cfg.validate()
    assert (cfg.nx, cfg.ny, cfg.viscosity, cfg.velocity) == (1280, 512, .004, .01)
    assert cfg.collision == 'MRT' and cfg.y_wall_bc == 'bounce_back'
    assert runner.U * runner.D / runner.NU == 50.
    assert runner.CENTRES == ((600., 255.5), (626., 270.5), (626., 240.5))


def test_structure_rest_equilibrium_and_energy_decay():
    s = runner.Structure(zeta=.01)
    assert s.candidate(0.) == (0., 0.)
    assert s.mass == pytest.approx(10*3*math.pi*100)
    s.y, s.v = .2, 0.
    # One damped period: independent continuous solution at total elapsed time.
    for _ in range(runner.PERIOD):
        s.y, s.v = s.candidate(0.)
    t = runner.PERIOD
    a = s.zeta*s.omega
    w = s.omega*math.sqrt(1-s.zeta**2)
    expected = .2*math.exp(-a*t)*(math.cos(w*t)+a/w*math.sin(w*t))
    assert s.y == pytest.approx(expected, abs=2e-12)
    assert .5*s.mass*s.v*s.v+.5*s.stiffness*s.y*s.y < .5*s.stiffness*.2**2
    s.y, s.v = .3, 0.
    assert s.candidate(s.stiffness*.3) == pytest.approx((.3, 0.), abs=1e-15)


def test_report_uses_completed_rows_and_net_force():
    rows = np.zeros((4, 15))
    rows[:, 0] = np.arange(1, 5)
    rows[:, 1] = 2.
    rows[:, 3:9] = 1.
    got = runner.summarize(rows)
    assert got[0]['end_step'] == 4
    assert got[0]['y_rms_D'] == .1
    assert got[0]['fy_rms'] == 6.


@pytest.mark.parametrize('case', ['Z0', 'M2', 'R2'])
def test_zero_damping_cases_conserve_unforced_energy_and_match_forced_solution(case):
    s = runner.Structure(*runner.STRUCTURES[case])
    assert s.zeta == s.damping == 0.
    s.y, s.v = .2, 1.e-5
    y0, v0 = s.y, s.v
    energy = .5*s.mass*v0**2 + .5*s.stiffness*y0**2
    for _ in range(12345):
        s.y, s.v = s.candidate(0.)
    assert .5*s.mass*s.v**2 + .5*s.stiffness*s.y**2 == pytest.approx(energy, rel=2e-11)
    force, elapsed = 1.e-4, 3210
    s.y, s.v = y0, v0
    for _ in range(elapsed):
        s.y, s.v = s.candidate(force)
    phase = s.omega*elapsed
    equilibrium = force/s.stiffness
    expected_y = equilibrium+(y0-equilibrium)*math.cos(phase)+v0*math.sin(phase)/s.omega
    expected_v = -(y0-equilibrium)*s.omega*math.sin(phase)+v0*math.cos(phase)
    assert (s.y, s.v) == pytest.approx((expected_y, expected_v), abs=2e-11)


def test_predeclared_comparisons_change_structure_only():
    z, m, r = [runner.Structure(*runner.STRUCTURES[k]) for k in ['Z0', 'M2', 'R2']]
    assert m.mass/z.mass == pytest.approx(.2)
    assert m.stiffness/z.stiffness == pytest.approx(.2)
    assert r.mass == m.mass
    assert r.stiffness/m.stiffness == pytest.approx(.36)
    assert [runner.STEPS*s.frequency for s in [z, m, r]] == pytest.approx([60., 60., 36.])


@pytest.mark.parametrize('diameter', [20, 40, 60])
def test_diffusive_scaling_preserves_physical_geometry_and_duration(tmp_path, diameter):
    import json
    from CelerisLab.config import load_lbm_config
    scale = diameter/20
    raw = runner.config(diameter)
    p = tmp_path/'scaled.json'
    p.write_text(json.dumps(raw))
    cfg = load_lbm_config(str(p))
    cfg.validate()
    assert cfg.velocity*diameter/cfg.viscosity == pytest.approx(50.)
    assert (cfg.nx-1)/diameter == 1279/20
    assert (cfg.ny-2)/diameter == 510/20
    for original, mapped in zip(runner.CENTRES+runner.PROBES,
                               runner.scaled_points(runner.CENTRES+runner.PROBES, scale)):
        assert mapped[0]/diameter == pytest.approx(original[0]/20)
        assert (mapped[1]-.5)/diameter == pytest.approx((original[1]-.5)/20)
    old = runner.Structure(*runner.STRUCTURES['M2'])
    new = runner.Structure(2., old.frequency/scale**2, diameter=diameter)
    assert new.mass/old.mass == pytest.approx(scale**2)
    assert new.stiffness/old.stiffness == pytest.approx(1/scale**2)
    assert new.damping == 0.
    assert cfg.velocity/(new.frequency*diameter) == pytest.approx(5.)
    assert runner.STEPS*scale**2*cfg.velocity/diameter == pytest.approx(300.)
    assert runner.WARMUP*scale**2*cfg.velocity/diameter == pytest.approx(256.)
    # A physical held force maps as F_fine=F_coarse/scale in two dimensions.
    old.y, old.v = .3, .0002
    new.y, new.v = scale*old.y, old.v/scale
    expected = old.candidate(.0001)
    for _ in range(round(scale**2)):
        new.y, new.v = new.candidate(.0001/scale)
    assert (new.y/scale, new.v*scale) == pytest.approx(expected, abs=2e-12)


def test_scaled_summary_uses_requested_units_and_completed_rows():
    rows = np.zeros((5, 15))
    rows[:, 0] = np.arange(1, 6)
    rows[:, 1] = 4.
    got = runner.summarize(rows, diameter=40, block_steps=3)
    assert [(x['start_step'], x['end_step']) for x in got] == [(1, 3), (4, 5)]
    assert all(x['y_rms_D'] == .1 for x in got)
    assert runner.summarize(rows[:0], diameter=40) == []