"""Shared helpers for the per-scenario fixture builders (AZ-599).

Both `build_p01_fixtures.py` (still-image FT-P-01) and
`build_p02_fixtures.py` (Derkachi FT-P-02) shell out to the production
`gps-denied-replay` CLI and write the same minimal `observer_*.json`
config; the helpers below live here so there's one canonical
implementation.

Future per-scenario builders (FT-P-04 / FT-P-05 / FT-P-10 / …) should
also import from this module.
"""

from __future__ import annotations

import json
import logging
import subprocess
from pathlib import Path
from typing import Callable, Sequence

_LOG = logging.getLogger(__name__)

DEFAULT_CLI_BIN = "gps-denied-replay"


def run_gps_denied_replay(
    video: Path,
    tlog: Path,
    fdr_out: Path,
    *,
    cli_bin: str = DEFAULT_CLI_BIN,
    time_offset_ms: int = 0,
    extra_args: Sequence[str] = (),
    _runner: Callable[[Sequence[str]], subprocess.CompletedProcess] | None = None,
) -> subprocess.CompletedProcess:
    """Run ``gps-denied-replay`` as a subprocess.

    The `time_offset_ms` defaults to 0 because both b78 (synthetic
    stationary tlog) and b79 (Derkachi real-motion tlog) intentionally
    bypass auto-sync — b78 because there's no take-off signal, b79
    because the IMU CSV is already aligned with the video. Operators
    running this against truly independent tlog+video pairs SHOULD
    omit ``time_offset_ms`` and let the production auto-sync run.

    Raises ``subprocess.CalledProcessError`` on non-zero exit code.
    The default subprocess runner can be swapped via ``_runner`` for
    unit tests.
    """
    fdr_out.parent.mkdir(parents=True, exist_ok=True)
    cmd: list[str] = [
        cli_bin,
        "--video", str(video),
        "--tlog", str(tlog),
        "--time-offset-ms", str(time_offset_ms),
        "--fdr-out", str(fdr_out),
        *extra_args,
    ]
    _LOG.info("running: %s", " ".join(cmd))

    runner = _runner or (lambda c: subprocess.run(c, check=True, capture_output=True, text=True))
    return runner(cmd)


def write_observer_fixture(output_path: Path) -> None:
    """Write minimal `observer_<fc_kind>_<host>.json` so `get_observer` succeeds.

    Scenarios that only consume `wait_for_outbound` or `iter_records`
    still trigger `sitl_observer.get_observer(...)` for construction.
    Populate with safe defaults; scenarios that care about
    `read_gps_state` carry their own observer fixtures.
    """
    payload = {
        "gps_state": {
            "primary_source": "MAV",
            "last_position_lat_deg": 0.0,
            "last_position_lon_deg": 0.0,
            "last_position_alt_m": 0.0,
            "fix_quality": 3,
            "horizontal_accuracy_m": 1.0,
            "last_update_age_ms": 0,
        },
        "parameters": {},
    }
    output_path.parent.mkdir(parents=True, exist_ok=True)
    output_path.write_text(json.dumps(payload, indent=2))