from __future__ import annotations

import unittest

from backend.observability_utils import RequestMetricsRegistry, elapsed_ms, make_request_id


class ObservabilityUtilsTests(unittest.TestCase):
    def test_make_request_id_returns_short_hex_token(self) -> None:
        request_id = make_request_id()
        self.assertEqual(len(request_id), 12)
        int(request_id, 16)

    def test_request_metrics_registry_tracks_counts_and_errors(self) -> None:
        registry = RequestMetricsRegistry()
        registry.record("/api/ping", 200, 10.0)
        registry.record("/api/ping", 503, 30.0)

        snapshot = registry.snapshot()
        self.assertEqual(snapshot["total_requests"], 2)
        self.assertEqual(snapshot["total_errors"], 1)
        self.assertEqual(snapshot["routes"]["/api/ping"]["avg_duration_ms"], 20.0)
        self.assertEqual(snapshot["routes"]["/api/ping"]["last_status_code"], 503)

    def test_elapsed_ms_is_non_negative(self) -> None:
        value = elapsed_ms(0.0)
        self.assertGreaterEqual(value, 0.0)


if __name__ == "__main__":
    unittest.main()