from __future__ import annotations

import pytest
from django.core.cache import cache

from odm import PropagationError
from yksa_orbital import model_config as mc


@pytest.fixture(autouse=True)
def _clear_cache():
    cache.delete(mc.CACHE_KEY)
    yield
    cache.delete(mc.CACHE_KEY)


class _Backend:
    def __init__(self, result=None, error=None):
        self.result = result
        self.error = error
        self.calls = 0

    def model_config(self):
        self.calls += 1
        if self.error:
            raise self.error
        return self.result


def test_the_model_is_read_once_and_cached(monkeypatch):
    backend = _Backend({"decay": {"altitude_km": 105.0}})
    monkeypatch.setattr(mc, "get_backend", lambda name=None: backend)

    assert mc.model_config()["decay"]["altitude_km"] == 105.0
    mc.model_config()
    assert backend.calls == 1


def test_an_unreachable_sidecar_falls_back_without_raising(monkeypatch):
    backend = _Backend(error=PropagationError("unreachable"))
    monkeypatch.setattr(mc, "get_backend", lambda name=None: backend)

    assert mc.model_config()["unavailable"] is True


def test_the_failure_is_cached_too(monkeypatch):
    """Otherwise a sidecar that is down costs a connection attempt on every page
    render -- and against an unresolvable hostname each one is a DNS timeout, so
    a caption takes the page down instead of degrading."""
    backend = _Backend(error=PropagationError("unreachable"))
    monkeypatch.setattr(mc, "get_backend", lambda name=None: backend)

    mc.model_config()
    mc.model_config()
    mc.model_config()
    assert backend.calls == 1


def test_a_local_override_wins_over_the_sidecar(monkeypatch, settings):
    """When this deployment overrides a knob it really is flying something else,
    and a caption reading the sidecar's value would describe a different run."""
    backend = _Backend({"decay": {"altitude_km": 105.0}})
    monkeypatch.setattr(mc, "get_backend", lambda name=None: backend)
    settings.DECAY_ALTITUDE_KM = 120.0

    assert mc.setting("decay", "altitude_km") == 120.0


def test_an_unset_override_reads_the_sidecar(monkeypatch, settings):
    backend = _Backend({"decay": {"altitude_km": 105.0}})
    monkeypatch.setattr(mc, "get_backend", lambda name=None: backend)
    settings.DECAY_ALTITUDE_KM = None

    assert mc.setting("decay", "altitude_km") == 105.0