"""Shared paths, constants and small helpers for the cold_occulters study."""
import os
import ssl
import time
import urllib.parse
import urllib.request

import numpy as np

STUDY = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
DATA = os.path.join(STUDY, "data")
FIGS = os.path.join(STUDY, "figures")
RAW = os.environ.get("COLDOCC_RAW", "fermi_raw/cold_occulters")
for _d in (DATA, FIGS, RAW):
    os.makedirs(_d, exist_ok=True)

OGLE_FTP = "https://www.astrouw.edu.pl/ogle"
GAIA_TAP = "https://gea.esac.esa.int/tap-server/tap"
VIZIER_TAP = "https://tapvizier.cds.unistra.fr/TAPVizieR/tap"

# physical constants (SI)
H_PLANCK = 6.62607015e-34
C_LIGHT = 2.99792458e8
K_B = 1.380649e-23
SIGMA_SB = 5.670374419e-8
L_SUN = 3.828e26
R_SUN = 6.957e8
AU = 1.495978707e11
PC = 3.0856775814913673e16
G_NEWT = 6.67430e-11
M_SUN = 1.98847e30
YEAR = 365.25 * 86400.0
KMS_TO_AU_PER_YR = 1e3 * YEAR / AU          # 0.21095 au/yr per km/s
KMS_TO_PC_PER_YR = 1e3 * YEAR / PC          # 1.0227e-6 pc/yr per km/s
AU_PC = AU / PC                             # 4.848e-6 pc
# Einstein radius: r_E^2 = (4 G M / c^2) D_l D_ls / D_s ; in au^2 per (Msun kpc)
RE2_AU2_PER_MSUN_KPC = 4 * G_NEWT * M_SUN / C_LIGHT ** 2 * (1e3 * PC) / AU ** 2   # 8.144

T1AU = (L_SUN / (4 * np.pi * SIGMA_SB * AU ** 2)) ** 0.25      # 393.6 K: blackbody sphere of 1 au radiating 1 Lsun


def radius_au(L_lsun, T):
    """Radius of an opaque blackbody sphere re-radiating L at temperature T."""
    return np.sqrt(L_lsun) * (T1AU / np.asarray(T, float)) ** 2


def _ctx():
    return ssl.create_default_context()


def http_get(url, timeout=300, data=None, retries=3):
    last = None
    for k in range(retries):
        try:
            req = urllib.request.Request(url, data=data, headers={"User-Agent": "fermi-cold-occulters/1.0"})
            with urllib.request.urlopen(req, timeout=timeout, context=_ctx()) as r:
                return r.read()
        except Exception as e:      # noqa: BLE001  (retry on any network error)
            last = e
            time.sleep(3 * (k + 1))
    raise last


def fetch(url, path, timeout=900, min_bytes=1):
    """Download url to path unless a non-empty copy is cached."""
    if os.path.exists(path) and os.path.getsize(path) >= min_bytes:
        return path
    os.makedirs(os.path.dirname(path), exist_ok=True)
    blob = http_get(url, timeout=timeout)
    with open(path + ".part", "wb") as f:
        f.write(blob)
    os.replace(path + ".part", path)
    return path


def tap_sync(base, adql, fmt="csv", timeout=600):
    data = urllib.parse.urlencode({"REQUEST": "doQuery", "LANG": "ADQL", "FORMAT": fmt, "QUERY": adql}).encode()
    return http_get(base + "/sync", timeout=timeout, data=data)


def poisson_ul(n_obs, cl=0.95):
    """Classical one-sided Poisson upper limit on the mean for n_obs observed events, no background."""
    from scipy.stats import chi2
    return 0.5 * chi2.ppf(cl, 2 * (n_obs + 1))