"""Regression checks for the finite P2 event/REMESH reference example."""

from __future__ import annotations

import json
from fractions import Fraction
from pathlib import Path

import pytest

import tnfr.physics as physics
import tnfr.physics.event_remesh_reference as reference_module
from tests.example_protocol_helpers import assert_prebuilt_report_main, load_example

EXAMPLE_PATH = (
    Path(__file__).resolve().parents[2]
    / "examples"
    / "02_physics_regimes"
    / "166_event_remesh_reference_family.py"
)


@pytest.fixture(scope="module")
def example_and_protocol():
    example = load_example(EXAMPLE_PATH)
    protocol = example.run_protocol()
    return example, protocol, example.build_report(protocol)


def test_module_and_stub_expose_the_reference_api() -> None:
    expected = {
        "P2EventRemeshMeshReferenceObservation",
        "P2EventRemeshReferenceFamilyObservation",
        "observe_p2_event_remesh_reference_family",
    }

    assert set(reference_module.__all__) == expected
    stub = (
        Path(reference_module.__file__).with_suffix(".pyi").read_text(encoding="utf-8")
    )
    assert "class P2EventRemeshMeshReferenceObservation" in stub
    assert "class P2EventRemeshReferenceFamilyObservation" in stub
    assert "def observe_p2_event_remesh_reference_family" in stub
    assert expected <= set(physics.__all__)
    assert (
        physics.P2EventRemeshMeshReferenceObservation
        is reference_module.P2EventRemeshMeshReferenceObservation
    )
    assert (
        physics.P2EventRemeshReferenceFamilyObservation
        is reference_module.P2EventRemeshReferenceFamilyObservation
    )
    assert (
        physics.observe_p2_event_remesh_reference_family
        is reference_module.observe_p2_event_remesh_reference_family
    )


def test_example_executes_the_expected_two_four_eight_meshes(
    example_and_protocol,
) -> None:
    _, protocol, _ = example_and_protocol
    reference = protocol["reference"]

    assert all(passed for _, passed in reference.conditions)
    assert tuple(len(mesh.exact_segment_durations) for mesh in reference.meshes) == (
        2,
        4,
        8,
    )
    assert reference.exact_euler_factors == (
        Fraction(1, 4),
        Fraction(81, 256),
        Fraction(5_764_801, 16_777_216),
    )
    assert reference.exact_quadratic_factor_error_upper_bounds == (
        Fraction(1, 4),
        Fraction(1, 8),
        Fraction(1, 16),
    )


def test_report_separates_the_finite_result_from_open_claims(
    example_and_protocol,
) -> None:
    _, _, report = example_and_protocol
    encoded = json.dumps(report, allow_nan=False, separators=(",", ":"))

    assert len(encoded) < 7000
    assert report["reference_family_certified"]
    assert [item["segment_count"] for item in report["meshes"]] == [2, 4, 8]
    assert report["strict_proper_subdivision_improvement"]
    assert all(item["runtime_residual_linf"] == "0/1" for item in report["meshes"])
    assert report["scope"] == {
        "compatible_finite_p2_problem": True,
        "binary64_asymptotic_convergence": False,
        "arbitrary_glyph_or_mixed_mode": False,
        "soft_clipping": False,
        "changing_support_or_metric": False,
        "generic_mesh_convergence": False,
        "solver_order": False,
        "repeated_runtime_stability": False,
        "future_stability": False,
    }

    # These claims belong to the real report, independently of CLI wiring.
    assert report["claim"] == "finite exact P2 event/REMESH reference family"
    assert report["reference_family_certified"]


def test_main_emits_finite_json(
    monkeypatch: pytest.MonkeyPatch,
    capsys: pytest.CaptureFixture[str],
) -> None:
    assert_prebuilt_report_main(load_example(EXAMPLE_PATH), monkeypatch, capsys)