import importlib.util
import sys

import pytest
from prometheus_client.metrics import MetricWrapperBase

from litellm.accounting import metrics
from litellm.accounting.metrics import Cadence, record_backlog, record_storage
from litellm.repositories.accounting_delivery_repository import DeliveryBacklog, DeliveryStorage

_BACKLOG = DeliveryBacklog(pending_count=4, parked_count=1, oldest_pending_seconds=-3.0)
_STORAGE = DeliveryStorage(batch_count=7, table_bytes=8192)


def _sample(metric: MetricWrapperBase, suffix: str = "") -> float:
    family = metric.collect()[0]
    return next(sample.value for sample in family.samples if sample.name == family.name + suffix)


def test_delivery_metrics_publish_backlog_and_clamp_clock_skew() -> None:
    instruments = metrics._INSTRUMENTS
    assert instruments is not None
    batches_before = _sample(instruments.batch_time, "_count")

    record_backlog(_BACKLOG, 0.5)
    record_storage(_STORAGE)

    assert (
        _sample(instruments.pending),
        _sample(instruments.parked),
        _sample(instruments.oldest),
        _sample(instruments.batch_count),
        _sample(instruments.table_bytes),
    ) == (4.0, 1.0, 0.0, 7.0, 8192.0)
    assert _sample(instruments.batch_time, "_count") == batches_before + 1


def test_delivery_metrics_are_skipped_when_prometheus_client_is_not_installed(
    monkeypatch: pytest.MonkeyPatch,
) -> None:
    monkeypatch.setitem(sys.modules, "prometheus_client", None)
    spec = importlib.util.spec_from_file_location("accounting_metrics_without_prometheus", metrics.__file__)
    assert spec is not None and spec.loader is not None
    module = importlib.util.module_from_spec(spec)
    monkeypatch.setitem(sys.modules, spec.name, module)

    spec.loader.exec_module(module)

    assert module.record_backlog(_BACKLOG, 0.5) is None
    assert module.record_storage(_STORAGE) is None


def test_cadence_is_due_once_per_interval() -> None:
    now = [100.0]
    cadence = Cadence(lambda: now[0])

    observed = []
    for moment in (100.0, 101.0, 999.9, 1000.0, 1000.0, 1899.0, 1900.0):
        now[0] = moment
        observed.append(cadence.due(900))

    assert observed == [True, False, False, True, False, False, True]