"""Shared paths, constants and small helpers for the mdwarf_early study."""
import os
import numpy as np

CODE_DIR = os.path.dirname(os.path.abspath(__file__))
STUDY_DIR = os.path.dirname(CODE_DIR)
DATA_DIR = os.path.join(STUDY_DIR, "data")
FIG_DIR = os.path.join(STUDY_DIR, "figures")
RAW_DIR = os.environ.get("FERMI_RAW", "fermi_raw/mdwarf_early")
for d in (DATA_DIR, FIG_DIR, RAW_DIR):
    os.makedirs(d, exist_ok=True)

SEED = 20261011
V_ESC_EARTH = 11.186          # km/s
T0_GYR = 13.79                # age of the Universe today (Planck 2018)
M_DWARF_MAX_MASS = 0.60       # Msun; boundary used for "M dwarf" in the earliness model
A_EARTH_GYR = 4.54            # age of the Earth when a technological civilisation appeared
# Floor ("lapse rate") on any extrapolated retention probability.  The logistic tail of the fitted
# shoreline reaches 1e-10 ... 1e-59 for late-M hosts; with no decisive habitable-zone verdict and
# 14 airless verdicts in total, the data cannot support a retention probability below ~0.1 for any
# class of planet, so such tails are a property of the functional form, not of the data.  We mix the
# logistic with a constant: f_eff = eps + (1 - eps) f.  Default eps = 1e-3; 0 and 1e-2 are run as
# sensitivities (referee point 5).
F_ATM_FLOOR = 1.0e-3

# Flat LCDM (Planck 2018)
H0 = 67.4                      # km/s/Mpc
OMEGA_M = 0.315
OMEGA_L = 1.0 - OMEGA_M
H0_PER_GYR = H0 * 1.0227e-3    # 1 km/s/Mpc = 1.0227e-3 / Gyr


def rocky_mass_from_radius(r_earth):
    """Earth-like-composition mass-radius relation, R = M^0.27 (Zeng et al. 2016 approx.)."""
    return np.asarray(r_earth, dtype=float) ** (1.0 / 0.27)


def teq_from_insolation(s_earth):
    """Zero-albedo, full-redistribution equilibrium temperature [K]."""
    return 278.5 * np.asarray(s_earth, dtype=float) ** 0.25