"""Unit tests for ``runner.helpers.mavproxy_tlog_reader.iter_messages``.

AZ-416 fills in the pymavlink-backed body; AZ-406 committed the public
surface. These tests synthesise a tiny tlog on the fly so the parser
can be exercised without needing a captured `.tlog` artifact.
"""

from __future__ import annotations

import struct
from pathlib import Path

import pytest
from pymavlink.dialects.v20 import ardupilotmega as mavlink

from runner.helpers.mavproxy_tlog_reader import (
    TlogMessage,
    count_by_type,
    iter_messages,
)

_SRC_SYSTEM = 1
_SRC_COMPONENT = mavlink.MAV_COMP_ID_AUTOPILOT1
_BASE_TS_US = 1_700_000_000_000_000


def _write_tlog(tlog_path: Path, records: list[tuple[int, bytes]]) -> Path:
    """Write a synthetic tlog: ``[8B big-endian ts_us][raw frame]`` per record."""
    with tlog_path.open("wb") as fh:
        for ts_us, payload in records:
            fh.write(struct.pack(">Q", ts_us))
            fh.write(payload)
    return tlog_path


def _make_mav() -> mavlink.MAVLink:
    return mavlink.MAVLink(
        file=None,
        srcSystem=_SRC_SYSTEM,
        srcComponent=_SRC_COMPONENT,
    )


def _heartbeat(mav: mavlink.MAVLink) -> bytes:
    return mav.heartbeat_encode(
        type=mavlink.MAV_TYPE_FIXED_WING,
        autopilot=mavlink.MAV_AUTOPILOT_ARDUPILOTMEGA,
        base_mode=mavlink.MAV_MODE_FLAG_AUTO_ENABLED,
        custom_mode=10,
        system_status=mavlink.MAV_STATE_ACTIVE,
    ).pack(mav)


def _gps_raw_int(mav: mavlink.MAVLink, *, fix_type: int = 3, eph: int = 100) -> bytes:
    return mav.gps_raw_int_encode(
        time_usec=_BASE_TS_US,
        fix_type=fix_type,
        lat=487750000,
        lon=375940000,
        alt=280000,
        eph=eph,
        epv=200,
        vel=12000,
        cog=18000,
        satellites_visible=12,
    ).pack(mav)


def _gps_input(mav: mavlink.MAVLink) -> bytes:
    return mav.gps_input_encode(
        time_usec=_BASE_TS_US,
        gps_id=0,
        ignore_flags=0,
        time_week_ms=0,
        time_week=0,
        fix_type=3,
        lat=487750000,
        lon=375940000,
        alt=280.0,
        hdop=1.0,
        vdop=2.0,
        vn=10.0,
        ve=5.0,
        vd=0.5,
        speed_accuracy=0.3,
        horiz_accuracy=1.0,
        vert_accuracy=2.0,
        satellites_visible=12,
    ).pack(mav)


def test_iter_messages_raises_on_missing_file(tmp_path: Path) -> None:
    # Act / Assert
    with pytest.raises(FileNotFoundError, match="tlog not found"):
        list(iter_messages(tmp_path / "absent.tlog"))


def test_iter_messages_yields_message_type_and_fields(tmp_path: Path) -> None:
    """A single heartbeat round-trips through iter_messages."""
    # Arrange
    mav = _make_mav()
    tlog = _write_tlog(tmp_path / "single.tlog", [(_BASE_TS_US, _heartbeat(mav))])

    # Act
    msgs = list(iter_messages(tlog))

    # Assert
    assert len(msgs) == 1
    m = msgs[0]
    assert isinstance(m, TlogMessage)
    assert m.msg_type == "HEARTBEAT"
    assert m.fields["autopilot"] == mavlink.MAV_AUTOPILOT_ARDUPILOTMEGA
    assert "mavpackettype" not in m.fields  # excluded by the impl


def test_iter_messages_preserves_order(tmp_path: Path) -> None:
    """Multiple records are yielded oldest-first."""
    # Arrange
    mav = _make_mav()
    tlog = _write_tlog(
        tmp_path / "ordered.tlog",
        [
            (_BASE_TS_US + 0, _heartbeat(mav)),
            (_BASE_TS_US + 1_000_000, _gps_raw_int(mav)),
            (_BASE_TS_US + 2_000_000, _gps_input(mav)),
        ],
    )

    # Act
    types = [m.msg_type for m in iter_messages(tlog)]

    # Assert
    assert types == ["HEARTBEAT", "GPS_RAW_INT", "GPS_INPUT"]


def test_iter_messages_timestamp_in_microseconds(tmp_path: Path) -> None:
    """``msg._timestamp`` is seconds; we expose microseconds."""
    # Arrange
    mav = _make_mav()
    tlog = _write_tlog(tmp_path / "ts.tlog", [(_BASE_TS_US + 5_000_000, _heartbeat(mav))])

    # Act
    msg = next(iter_messages(tlog))

    # Assert — pymavlink rounds to its frame timestamp; tolerate ±1ms slop.
    assert abs(msg.timestamp_us - (_BASE_TS_US + 5_000_000)) <= 1_000


def test_iter_messages_signed_flag_default_false(tmp_path: Path) -> None:
    """Plain pymavlink-encoded frame is NOT signed → signed=False."""
    # Arrange
    mav = _make_mav()
    tlog = _write_tlog(tmp_path / "u.tlog", [(_BASE_TS_US, _heartbeat(mav))])

    # Act
    msg = next(iter_messages(tlog))

    # Assert
    assert msg.signed is False


def test_count_by_type_tallies_correctly(tmp_path: Path) -> None:
    """count_by_type runs iter_messages and aggregates the type counts."""
    # Arrange
    mav = _make_mav()
    tlog = _write_tlog(
        tmp_path / "mixed.tlog",
        [
            (_BASE_TS_US + 0, _heartbeat(mav)),
            (_BASE_TS_US + 1, _heartbeat(mav)),
            (_BASE_TS_US + 2, _gps_raw_int(mav)),
        ],
    )

    # Act
    counts = count_by_type(tlog)

    # Assert
    assert counts["HEARTBEAT"] == 2
    assert counts["GPS_RAW_INT"] == 1