"""Veil conditions readout — the sky and the field, in one call.

Composes the two real-world signals the app already computes:

  sky          - app.celestial.veil_thinness(): moon phase/illumination and
                 (when a longitude is offered) proximity to true solar
                 midnight. Pure math, always present.
  geomagnetic  - app.geomagnetic.geomagnetic_cache.reading(): NOAA's
                 planetary Kp from cache. May be None on a cold cache or
                 when NOAA is unreachable — that is a valid answer, not an
                 error, and the frontend simply shows fewer lines.

`lon` is accepted as a raw string and parsed by hand so a malformed or
out-of-range value degrades to the moon-only reading instead of a 422 —
the conditions strip must never fail because a browser sent junk.
"""

import math

from fastapi import APIRouter

from app.celestial import veil_thinness
from app.geomagnetic import geomagnetic_cache

router = APIRouter(prefix="/api", tags=["conditions"])


def _parse_longitude(raw: str | None) -> float | None:
    """A usable longitude in [-180, 180], or None for anything else."""
    if raw is None:
        return None
    try:
        lon = float(raw)
    except (TypeError, ValueError):
        return None
    if not math.isfinite(lon) or not -180.0 <= lon <= 180.0:
        return None
    return lon


@router.get("/conditions")
async def get_conditions(lon: str | None = None):
    return {
        "sky": veil_thinness(_parse_longitude(lon)),
        "geomagnetic": await geomagnetic_cache.reading(),
    }