"""Behavioural tests for the AZ-408 FC inbound proxy patch.

Covers AC-3 (video↔proxy alignment ≤ 40 ms — verified end-to-end via the
fake clock here; the runtime path observes the same invariant) and the
proxy's pass-through / spoof-replace semantics.
"""

from __future__ import annotations

import json
from pathlib import Path

import pytest

from fixtures.injectors.fc_proxy import BlackoutSpoofProxy, SpoofGpsRecord


class _FakeClock:
    """Monotonic ms clock that the test advances manually."""

    def __init__(self, start_ms: int = 0) -> None:
        self.now_ms = start_ms

    def __call__(self) -> int:
        return self.now_ms

    def advance(self, ms: int) -> None:
        self.now_ms += ms


def _spoof_records() -> list[SpoofGpsRecord]:
    return [
        SpoofGpsRecord(monotonic_ms=1000 + i * 100, lat_deg=50.0 + i * 0.001,
                       lon_deg=36.1, alt_m=300.0, fix_type=3, hdop=1.0)
        for i in range(5)
    ]


def test_proxy_passes_through_outside_window() -> None:
    # Arrange — schedule the first blackout 500 ms in the future. The
    # activate() call binds proxy_time(now) = 0; the window opens at
    # window_start_ms = 500 in proxy time. Now (proxy_time = 0) is
    # outside [500, 1000], so the proxy must pass through.
    clock = _FakeClock(start_ms=1000)
    proxy = BlackoutSpoofProxy(window_start_ms=500, window_end_ms=1000,
                               spoof_gps=_spoof_records())
    proxy.activate(now_ms_provider=clock, first_blackout_ms=1500)
    msg = {"lat_deg": 49.9, "lon_deg": 36.0, "alt_m": 280.0}

    # Act
    out = proxy.process_inbound_message(msg)

    # Assert
    assert out == msg
    assert "__spoofed__" not in out


def test_proxy_spoofs_inside_window() -> None:
    # Arrange
    clock = _FakeClock(start_ms=0)
    proxy = BlackoutSpoofProxy(window_start_ms=0, window_end_ms=500,
                               spoof_gps=_spoof_records())
    proxy.activate(now_ms_provider=clock, first_blackout_ms=0)
    msg = {"lat_deg": 49.9, "lon_deg": 36.0, "alt_m": 280.0}

    # Act — clock=0 ⇒ proxy_time(0) = 0 (inside window)
    out = proxy.process_inbound_message(msg)

    # Assert
    assert out["__spoofed__"] is True
    assert out["lat_deg"] != msg["lat_deg"]
    assert out["fix_type"] == 3


def test_proxy_returns_to_passthrough_after_window() -> None:
    # Arrange
    clock = _FakeClock(start_ms=0)
    proxy = BlackoutSpoofProxy(window_start_ms=0, window_end_ms=500,
                               spoof_gps=_spoof_records())
    proxy.activate(now_ms_provider=clock, first_blackout_ms=0)

    # Act — advance past end of window
    clock.advance(1000)
    msg = {"lat_deg": 50.0, "lon_deg": 36.0, "alt_m": 300.0}
    out = proxy.process_inbound_message(msg)

    # Assert
    assert out == msg


def test_alignment_err_below_40ms_when_clock_matches_first_blackout() -> None:
    """AC-3: when the test harness calls activate() at the same ms the
    first blackout frame fires, alignment error is 0."""
    # Arrange
    clock = _FakeClock(start_ms=12_345)
    proxy = BlackoutSpoofProxy(window_start_ms=0, window_end_ms=500, spoof_gps=_spoof_records())

    # Act
    report = proxy.activate(now_ms_provider=clock, first_blackout_ms=12_345)

    # Assert
    assert report.alignment_err_ms == 0
    assert report.alignment_err_ms <= 40


def test_alignment_err_within_budget_under_normal_clock_skew() -> None:
    """Real harness can have a 30 ms skew between video & proxy; still inside AC-3."""
    # Arrange
    clock = _FakeClock(start_ms=12_400)
    proxy = BlackoutSpoofProxy(window_start_ms=0, window_end_ms=500, spoof_gps=_spoof_records())

    # Act — first_blackout_ms is 30 ms earlier than clock (harness skew)
    report = proxy.activate(now_ms_provider=clock, first_blackout_ms=12_370)

    # Assert
    assert report.alignment_err_ms == 30
    assert report.alignment_err_ms <= 40


def test_exhausting_spoof_list_repeats_last() -> None:
    """When the spoofed-GPS list is drained, the FC keeps seeing the last record."""
    # Arrange
    clock = _FakeClock(start_ms=0)
    spoofs = _spoof_records()
    proxy = BlackoutSpoofProxy(window_start_ms=0, window_end_ms=10_000, spoof_gps=spoofs)
    proxy.activate(now_ms_provider=clock, first_blackout_ms=0)

    # Act — pull 10 frames (more than the 5 in the list)
    outs = [proxy.process_inbound_message({"lat_deg": 0, "lon_deg": 0, "alt_m": 0}) for _ in range(10)]

    # Assert — last 5 outputs all reuse the final spoof record
    last = spoofs[-1]
    for o in outs[-3:]:
        assert o["lat_deg"] == last.lat_deg
        assert o["lon_deg"] == last.lon_deg


def test_from_schedule_file_round_trip(tmp_path: Path) -> None:
    # Arrange
    sched_path = tmp_path / "schedule.json"
    sched_path.write_text(
        json.dumps(
            {
                "window_start_ms": 0,
                "window_end_ms": 200,
                "max_alignment_err_ms": 40.0,
                "blackout_frame_indices": [0, 1, 2],
                "spoof_gps": [
                    {"monotonic_ms": 0, "lat_deg": 50.0, "lon_deg": 36.0,
                     "alt_m": 300.0, "fix_type": 3, "hdop": 1.0},
                ],
            }
        )
    )

    # Act
    proxy = BlackoutSpoofProxy.from_schedule_file(sched_path)
    proxy.activate(now_ms_provider=lambda: 0)
    out = proxy.process_inbound_message({"lat_deg": 0, "lon_deg": 0, "alt_m": 0})

    # Assert
    assert out["__spoofed__"] is True
    assert out["lat_deg"] == 50.0


def test_from_schedule_file_missing_raises(tmp_path: Path) -> None:
    # Arrange / Act / Assert
    with pytest.raises(FileNotFoundError):
        BlackoutSpoofProxy.from_schedule_file(tmp_path / "missing.json")


def test_process_before_activate_raises() -> None:
    # Arrange
    proxy = BlackoutSpoofProxy(window_start_ms=0, window_end_ms=100, spoof_gps=_spoof_records())
    # Act / Assert
    with pytest.raises(RuntimeError, match="not activated"):
        proxy.process_inbound_message({})


def test_in_window_false_before_activate() -> None:
    # Arrange
    proxy = BlackoutSpoofProxy(window_start_ms=0, window_end_ms=100, spoof_gps=[])
    # Act / Assert
    assert proxy.in_window() is False