"""Shared material definitions for ELoss analysis scripts."""

import pycatima as catima

R_GAS_CONSTANT = 8.3144  # J/mol/K


def _gas_molar_density(p_torr, temp_k):
    """Return molar density in mol/m^3 from pressure (Torr) and temperature (K)."""
    p_pa = p_torr * 133.322
    return p_pa / (R_GAS_CONSTANT * temp_k)


def build_material(medium, p_torr, temp_k):
    """
    Build a CATIMA material and return (material, density_g_cm3).

    Supported media names:
      - He
      - PureHe
      - Si
      - kapton
    """
    medium_key = medium.strip().lower()

    if medium_key == "he":
        m_he = 4.0026
        m_c = 12.0000
        m_o = 15.9949

        material_def = [
            (m_he, 2, 0.96),
            (m_c, 6, 0.04),
            (m_o, 8, 0.08),
        ]

        molar_density = _gas_molar_density(p_torr, temp_k)
        m_mix_avg = 0.96 * m_he + 0.04 * (m_c + 2 * m_o)
        rho_g_cm3 = (molar_density * m_mix_avg) / 1e6

    elif medium_key == "purehe":
        m_he = 4.0026
        material_def = [(m_he, 2, 1.0)]

        molar_density = _gas_molar_density(p_torr, temp_k)
        m_mix_avg = m_he
        rho_g_cm3 = (molar_density * m_mix_avg) / 1e6

    elif medium_key == "si":
        m_si = 28.084
        material_def = [(m_si, 14, 1.0)]
        rho_g_cm3 = 2.33

    elif medium_key == "kapton":
        m_h = 1.008
        m_c = 12.011
        m_n = 14.007
        m_o = 15.999

        material_def = [
            (m_h, 1, 0.026),
            (m_c, 6, 0.691),
            (m_n, 7, 0.073),
            (m_o, 8, 0.209),
        ]
        rho_g_cm3 = 1.42

    else:
        raise ValueError(f"Unsupported medium: {medium}")

    material = catima.Material(material_def)
    material.density(rho_g_cm3)
    return material, rho_g_cm3