"""Unit tests for the LatencyObserver (TASK-02-06)."""

from __future__ import annotations

import pytest

from server.latency import LatencyObserver, LatencyRecord


def test_latency_record_e2e():
    r = LatencyRecord(transcript_ready_ms=100.0, tts_first_audio_ms=650.0)
    assert r.e2e_asr_to_tts_ms == 550.0


def test_latency_record_missing_segments():
    r = LatencyRecord(transcript_ready_ms=100.0)
    assert r.e2e_asr_to_tts_ms is None
    r2 = LatencyRecord(tts_first_audio_ms=650.0)
    assert r2.e2e_asr_to_tts_ms is None


def test_latency_record_metric_dict():
    r = LatencyRecord(
        transcript_ready_ms=100.0, llm_first_token_ms=300.0, tts_first_audio_ms=650.0
    )
    m = r.as_metric()
    assert m["e2e_latency_ms"] == 550.0
    assert m["llm_first_token_ms"] == 300.0


def test_latency_observer_construction():
    """The observer constructs cleanly and starts with an empty state."""
    obs = LatencyObserver()
    assert obs.state.records == []
    assert obs.state.current.transcript_ready_ms is None


def test_latency_observer_state_reset_turn():
    """reset_turn archives the current record and starts a fresh one."""
    from server.latency import LatencyObserverState

    state = LatencyObserverState()
    state.current.transcript_ready_ms = 100.0
    state.current.tts_first_audio_ms = 650.0
    state.reset_turn()
    assert len(state.records) == 1
    assert state.records[0].e2e_asr_to_tts_ms == 550.0
    assert state.current.transcript_ready_ms is None