"""Unit tests for ``runner.helpers.ttff_evaluator`` (AZ-430 / NFT-PERF-03)."""

from __future__ import annotations

from pathlib import Path

import pytest

from runner.helpers import ttff_evaluator as te


def _iter(iter_id: str, ttff_s: float | None) -> te.ColdStartIteration:
    """One iteration sample with the implied first_emission_ms timestamp."""
    if ttff_s is None:
        return te.measure_iteration(
            iter_id, first_frame_arrival_ms=0, first_emission_ms=None
        )
    return te.measure_iteration(
        iter_id,
        first_frame_arrival_ms=0,
        first_emission_ms=int(ttff_s * 1000),
    )


# ───────────────────────── measure_iteration ─────────────────────────


def test_measure_iteration_happy_path() -> None:
    # Act
    s = te.measure_iteration(
        "it1", first_frame_arrival_ms=1_000, first_emission_ms=24_000
    )

    # Assert
    assert s.ttff_s == pytest.approx(23.0)
    assert s.emitted


def test_measure_iteration_missing_emission_returns_none() -> None:
    # Act
    s = te.measure_iteration(
        "it1", first_frame_arrival_ms=1_000, first_emission_ms=None
    )

    # Assert
    assert s.ttff_s is None
    assert not s.emitted


def test_measure_iteration_negative_ttff_raises() -> None:
    # Assert
    with pytest.raises(ValueError):
        te.measure_iteration(
            "it1", first_frame_arrival_ms=10_000, first_emission_ms=9_000
        )


def test_measure_iteration_zero_ttff_allowed() -> None:
    # Act
    s = te.measure_iteration(
        "it1", first_frame_arrival_ms=10_000, first_emission_ms=10_000
    )

    # Assert
    assert s.ttff_s == 0.0


# ───────────────────────── evaluate ─────────────────────────


def test_evaluate_clean_run_passes_all_acs() -> None:
    # Arrange — 10 iterations at 15..24 s
    iterations = [_iter(f"it{i}", 15.0 + i) for i in range(10)]

    # Act
    report = te.evaluate(iterations)

    # Assert
    assert report.iteration_count == 10
    assert report.passes_iteration_count
    assert report.missed_starts == 0
    assert report.passes_p95
    assert report.passes_max
    assert report.passes


def test_evaluate_below_min_iterations_fails_ac1() -> None:
    # Arrange
    iterations = [_iter(f"it{i}", 15.0) for i in range(9)]

    # Act
    report = te.evaluate(iterations)

    # Assert
    assert not report.passes_iteration_count
    assert not report.passes


def test_evaluate_p95_at_budget_passes() -> None:
    # Arrange — all 10 exactly at 30 s
    iterations = [_iter(f"it{i}", 30.0) for i in range(10)]

    # Act
    report = te.evaluate(iterations)

    # Assert
    assert report.p95_s == pytest.approx(30.0)
    assert report.passes_p95


def test_evaluate_p95_above_budget_fails() -> None:
    # Arrange — last 2 spike to 35 s; p95 will land in tail
    iterations = [_iter(f"it{i}", 15.0) for i in range(8)] + [
        _iter("it8", 35.0),
        _iter("it9", 35.0),
    ]

    # Act
    report = te.evaluate(iterations)

    # Assert
    assert report.p95_s is not None and report.p95_s > 30.0
    assert not report.passes_p95
    assert not report.passes


def test_evaluate_max_exceeds_budget_fails_even_when_p95_passes() -> None:
    # Arrange — N=20 dilutes the outlier's pull on linear-interp p95
    iterations = [_iter(f"it{i}", 15.0) for i in range(19)] + [_iter("it19", 46.0)]

    # Act
    report = te.evaluate(iterations)

    # Assert
    assert report.passes_p95  # outlier doesn't shift p95 with 20 samples
    assert not report.passes_max
    assert not report.passes


def test_evaluate_one_missed_start_fails() -> None:
    # Arrange
    iterations = [_iter(f"it{i}", 15.0) for i in range(9)] + [_iter("it9", None)]

    # Act
    report = te.evaluate(iterations)

    # Assert
    assert report.missed_starts == 1
    assert not report.passes_p95
    assert not report.passes_max
    assert not report.passes


def test_evaluate_empty_input_fails_iteration_count() -> None:
    # Act
    report = te.evaluate([])

    # Assert
    assert report.iteration_count == 0
    assert not report.passes_iteration_count
    assert not report.passes


def test_evaluate_custom_budgets_apply() -> None:
    # Arrange
    iterations = [_iter(f"it{i}", 40.0) for i in range(10)]

    # Act
    report = te.evaluate(iterations, p95_budget_s=45.0, max_budget_s=60.0)

    # Assert
    assert report.passes


# ───────────────────────── csv emit ─────────────────────────


def test_write_csv_evidence_emits_summary(tmp_path: Path) -> None:
    # Arrange
    iterations = [_iter(f"it{i}", 15.0 + i) for i in range(10)]
    report = te.evaluate(iterations)
    out_path = tmp_path / "nft-perf-03.csv"

    # Act
    te.write_csv_evidence(out_path, report)

    # Assert
    rows = out_path.read_text().splitlines()
    assert len(rows) == 2
    assert rows[0].startswith("iteration_count")
    assert "ac3_p95_passes" in rows[0]
    assert "ac4_max_passes" in rows[0]


def test_write_per_iteration_csv_one_row_per_iter(tmp_path: Path) -> None:
    # Arrange
    iterations = [_iter(f"it{i}", 15.0 + i) for i in range(3)]
    report = te.evaluate(iterations, min_iteration_count=3)
    out_path = tmp_path / "per-iter.csv"

    # Act
    te.write_per_iteration_csv(out_path, report)

    # Assert
    rows = out_path.read_text().splitlines()
    assert rows[0] == "iteration_id,first_frame_arrival_ms,first_emission_ms,ttff_s"
    assert len(rows) == 4