"""Unit tests for ``runner.helpers.msp_frame_observer`` (FT-P-09-iNav / AZ-417).

Covers AC-2 (≥4.5 Hz observed for 5 Hz target) and AC-3 (fix_type ≥3,
provider=MSP, numSat matches emitted value).
"""

from __future__ import annotations

import pytest

from runner.helpers.msp_frame_observer import (
    DEFAULT_TARGET_RATE_HZ,
    MIN_FIX_TYPE,
    MIN_OBSERVED_RATE_HZ,
    MSP2_SENSOR_GPS_FUNCTION_ID,
    REQUIRED_PROVIDER,
    InavGpsSnapshot,
    MspFrameSample,
    compute_rate_hz,
    count_frames_by_id,
    evaluate_inav_gps_state,
)


def _frames(rate_hz: float, n: int, function_id: int = MSP2_SENSOR_GPS_FUNCTION_ID) -> list[MspFrameSample]:
    """Synthetic frame stream at exactly ``rate_hz`` for ``n`` frames."""
    if rate_hz <= 0:
        raise ValueError("rate_hz must be > 0")
    period_ms = int(round(1000.0 / rate_hz))
    return [
        MspFrameSample(monotonic_ms=i * period_ms, function_id=function_id)
        for i in range(n)
    ]


def test_constants_match_spec() -> None:
    """The AC-2/AC-3 thresholds + IDs must match the spec text."""
    # Assert
    assert MSP2_SENSOR_GPS_FUNCTION_ID == 0x1F03
    assert DEFAULT_TARGET_RATE_HZ == 5.0
    assert MIN_OBSERVED_RATE_HZ == 4.5
    assert MIN_FIX_TYPE == 3
    assert REQUIRED_PROVIDER == "MSP"


def test_count_frames_by_id_filters_correctly() -> None:
    """Mixed-ID stream tallies per function ID."""
    # Arrange
    samples = [
        MspFrameSample(0, MSP2_SENSOR_GPS_FUNCTION_ID),
        MspFrameSample(100, 0x1F04),
        MspFrameSample(200, MSP2_SENSOR_GPS_FUNCTION_ID),
        MspFrameSample(300, MSP2_SENSOR_GPS_FUNCTION_ID),
    ]

    # Act
    counts = count_frames_by_id(samples)

    # Assert
    assert counts[MSP2_SENSOR_GPS_FUNCTION_ID] == 3
    assert counts[0x1F04] == 1


def test_compute_rate_at_target_passes() -> None:
    """5 Hz over 60 s window passes the ≥4.5 Hz minimum."""
    # Arrange — 60s at 5Hz = 301 samples (inclusive of t=0 and t=60000).
    samples = _frames(rate_hz=5.0, n=301)

    # Act
    report = compute_rate_hz(samples)

    # Assert
    assert report.frame_count == 301
    assert report.observed_rate_hz == pytest.approx(5.0, abs=0.01)
    assert report.passes is True


def test_compute_rate_at_boundary_passes() -> None:
    """Exactly 4.5 Hz passes (boundary is inclusive)."""
    # Arrange
    samples = _frames(rate_hz=4.5, n=46)  # 10s @ 4.5Hz

    # Act
    report = compute_rate_hz(samples)

    # Assert
    assert report.observed_rate_hz == pytest.approx(4.5, abs=0.05)
    assert report.passes is True


def test_compute_rate_below_minimum_fails() -> None:
    """3 Hz observed → fails the ≥4.5 Hz minimum."""
    # Arrange
    samples = _frames(rate_hz=3.0, n=31)  # 10s @ 3Hz

    # Act
    report = compute_rate_hz(samples)

    # Assert
    assert report.observed_rate_hz == pytest.approx(3.0, abs=0.05)
    assert report.passes is False


def test_compute_rate_zero_samples_does_not_pass() -> None:
    """Empty input → zero count, zero rate, does not pass."""
    # Act
    report = compute_rate_hz([])

    # Assert
    assert report.frame_count == 0
    assert report.window_ms == 0
    assert report.observed_rate_hz == 0.0
    assert report.passes is False


def test_compute_rate_single_sample_does_not_pass() -> None:
    """One sample yields no window → does not pass."""
    # Arrange
    samples = [MspFrameSample(0, MSP2_SENSOR_GPS_FUNCTION_ID)]

    # Act
    report = compute_rate_hz(samples)

    # Assert
    assert report.frame_count == 1
    assert report.window_ms == 0
    assert report.passes is False


def test_compute_rate_filters_function_id() -> None:
    """Frames with a different function_id are ignored in the rate calc."""
    # Arrange
    samples = (
        _frames(rate_hz=5.0, n=51, function_id=MSP2_SENSOR_GPS_FUNCTION_ID)
        + _frames(rate_hz=10.0, n=101, function_id=0x1F04)
    )

    # Act
    report = compute_rate_hz(samples, function_id=MSP2_SENSOR_GPS_FUNCTION_ID)

    # Assert
    assert report.frame_count == 51
    assert report.observed_rate_hz == pytest.approx(5.0, abs=0.01)


def test_compute_rate_rejects_negative_minimum() -> None:
    # Act / Assert
    with pytest.raises(ValueError, match="min_required_hz"):
        compute_rate_hz([], min_required_hz=-1.0)


def test_evaluate_gps_state_passes_at_minimum_fix() -> None:
    """fix_type=3, provider=MSP, numSat=10 (matches emitted) → AC-3 pass."""
    # Arrange
    snapshot = InavGpsSnapshot(fix_type=3, num_sat=10, provider="MSP")

    # Act
    report = evaluate_inav_gps_state(snapshot, expected_num_sat=10)

    # Assert
    assert report.fix_type_ok is True
    assert report.provider_ok is True
    assert report.num_sat_ok is True
    assert report.passes is True


def test_evaluate_gps_state_fails_on_low_fix_type() -> None:
    """fix_type=2 < 3 → AC-3 fail."""
    # Arrange
    snapshot = InavGpsSnapshot(fix_type=2, num_sat=10, provider="MSP")

    # Act
    report = evaluate_inav_gps_state(snapshot, expected_num_sat=10)

    # Assert
    assert report.fix_type_ok is False
    assert report.passes is False


def test_evaluate_gps_state_fails_on_wrong_provider() -> None:
    """provider != MSP → AC-3 fail (fallback to internal GPS)."""
    # Arrange
    snapshot = InavGpsSnapshot(fix_type=3, num_sat=10, provider="INTERNAL")

    # Act
    report = evaluate_inav_gps_state(snapshot, expected_num_sat=10)

    # Assert
    assert report.provider_ok is False
    assert report.passes is False


def test_evaluate_gps_state_fails_on_num_sat_mismatch() -> None:
    """numSat reported by iNav must match the value emitted by SUT."""
    # Arrange
    snapshot = InavGpsSnapshot(fix_type=3, num_sat=12, provider="MSP")

    # Act
    report = evaluate_inav_gps_state(snapshot, expected_num_sat=10)

    # Assert
    assert report.num_sat_ok is False
    assert report.passes is False


def test_evaluate_gps_state_rejects_negative_expected_num_sat() -> None:
    # Arrange
    snapshot = InavGpsSnapshot(fix_type=3, num_sat=10, provider="MSP")

    # Act / Assert
    with pytest.raises(ValueError, match="expected_num_sat"):
        evaluate_inav_gps_state(snapshot, expected_num_sat=-1)