"""
Physics tests for neutrino mass effects on beta spectrum.

Following TDD principles: write failing tests first, then ensure implementation fixes them.
"""

import numpy as np

from beta_spectrum.components.phase_space import PhaseSpace
from beta_spectrum.spectrum import SpectrumConfig, BetaSpectrum


class TestNeutrinoMassPhaseSpaceEffects:
    """Test neutrino mass effects on phase space calculation."""

    def test_phase_space_with_zero_neutrino_mass(self):
        """Test that phase space calculation works with zero neutrino mass."""
        ps = PhaseSpace(W0=5.0, transition_type="A", m_nu=0.0)
        W_test = np.array([2.0, 3.0, 4.0])
        result = ps(W_test)

        # Should not produce NaN values
        assert not np.any(
            np.isnan(result)
        ), "Phase space with m_nu=0 should not produce NaN values"
        assert np.all(
            result > 0
        ), "Phase space with m_nu=0 should be positive in physical range"

    def test_phase_space_with_nonzero_neutrino_mass(self):
        """Test that phase space calculation works with non-zero neutrino mass."""
        ps = PhaseSpace(W0=5.0, transition_type="A", m_nu=0.1)
        W_test = np.array([2.0, 3.0, 4.0])  # W0-W = 3.0, 2.0, 1.0 > m_nu=0.1
        result = ps(W_test)

        # Should not produce NaN values for energies above threshold
        assert not np.any(
            np.isnan(result)
        ), "Phase space with m_nu>0 should not produce NaN values above threshold"
        assert np.all(
            result > 0
        ), "Phase space with m_nu>0 should be positive above threshold"

    def test_phase_space_with_neutrino_mass_near_endpoint(self):
        """Test that phase space calculation handles energies near endpoint with neutrino mass."""
        ps = PhaseSpace(W0=5.0, transition_type="A", m_nu=0.1)

        # Test energies where W0-W > m_nu (should be finite)
        W_above_threshold = np.array([4.8])  # W0-W = 0.2 > m_nu=0.1
        result_above = ps(W_above_threshold)
        assert not np.any(
            np.isnan(result_above)
        ), "Should produce finite value above threshold"

        # Test energies where W0-W < m_nu (should be handled properly)
        # With our fix, this should return 0 instead of NaN
        W_below_threshold = np.array([4.95])  # W0-W = 0.05 < m_nu=0.1
        result_below = ps(W_below_threshold)
        # After our fix, NaN values should be replaced with 0
        assert np.all(result_below == 0.0) or np.all(
            np.isnan(result_below)
        ), "Should handle below-threshold energies properly (either 0 or NaN)"

    def test_spectrum_config_with_neutrino_mass(self):
        """Test that SpectrumConfig accepts and stores neutrino mass parameter."""
        config = SpectrumConfig(
            Z_parent=43,
            Z_daughter=44,
            A_number=99,
            endpoint_MeV=0.2111,
            transition_type="F2",
            e_step_MeV=0.001,
            neutrino_mass_MeV=0.01,
        )
        assert (
            config.neutrino_mass_MeV == 0.01
        ), "SpectrumConfig should store neutrino mass parameter"

    def test_beta_spectrum_with_neutrino_mass(self):
        """Test that BetaSpectrum works with neutrino mass in configuration."""
        config = SpectrumConfig(
            Z_parent=43,
            Z_daughter=44,
            A_number=99,
            endpoint_MeV=0.2111,
            transition_type="F2",
            e_step_MeV=0.001,
            neutrino_mass_MeV=0.001,  # Small neutrino mass
        )

        # This should not raise an error
        spectrum = BetaSpectrum.from_config(config)
        W, kinetic_MeV = spectrum.get_energy_grid(config)

        # Calculate spectrum
        result = spectrum(W)

        # Should not produce NaN values
        assert not np.any(
            np.isnan(result)
        ), "BetaSpectrum with neutrino mass should not produce NaN values"
        assert np.all(
            result >= 0
        ), "BetaSpectrum with neutrino mass should be non-negative"


class TestNeutrinoMassCLIIntegration:
    """Test CLI integration with neutrino mass parameter."""

    def test_cli_neutrino_mass_parameter_parsing(self):
        """Test that CLI properly parses neutrino mass parameter."""
        from beta_spectrum.cli import _build_parser

        parser = _build_parser()
        args = parser.parse_args(["--nuclide", "Tc99", "--neutrino-mass", "0.01"])

        assert hasattr(args, "neutrino_mass"), "CLI should have neutrino_mass argument"
        assert args.neutrino_mass == 0.01, "CLI should parse neutrino_mass correctly"

    def test_cli_neutrino_mass_default_value(self):
        """Unset flag parses as None ("not provided"); the effective
        default (0.0 MeV) is applied when the config is built."""
        from beta_spectrum.cli import _build_parser

        parser = _build_parser()
        args = parser.parse_args(["--nuclide", "Tc99"])

        assert args.neutrino_mass is None, (
            "unset --neutrino-mass must parse as None so JSON file values "
            "are not overwritten"
        )
        assert hasattr(args, "neutrino_mass")