"""Pin Logitech C920 exposure so 360p stays 30 fps.

Aperture-priority + exposure_dynamic_framerate=1 lets the sensor sit at
~66 ms / gain 255 and drop to 15 fps. Manual 333 (0.1 ms units = 1/30 s)
with dyn-fps off holds the gst 30 fps request.
"""
from __future__ import annotations

import logging
import os
import subprocess

log = logging.getLogger("cameras.uvc-exposure")

# UVC: 1 = Manual Mode, 3 = Aperture Priority. Time unit is 0.1 ms.
AUTO_EXPOSURE_MANUAL = 1
EXPOSURE_TIME_30FPS = 333


def pin_cmd(
    device: str,
    *,
    auto_exposure: int = AUTO_EXPOSURE_MANUAL,
    exposure_time: int = EXPOSURE_TIME_30FPS,
    dynamic_framerate: int = 0,
) -> list[str]:
    cmd = [
        "v4l2-ctl",
        "-d",
        str(device),
        f"--set-ctrl=auto_exposure={int(auto_exposure)}",
        f"--set-ctrl=exposure_dynamic_framerate={int(dynamic_framerate)}",
    ]
    # Time is inactive under aperture-priority (3); setting it fails the whole pin.
    if int(auto_exposure) == AUTO_EXPOSURE_MANUAL:
        cmd.insert(4, f"--set-ctrl=exposure_time_absolute={int(exposure_time)}")
    return cmd


def pin_from_env() -> tuple[int, int, int]:
    ae = int(os.environ.get("VIDEO_AUTO_EXPOSURE", str(AUTO_EXPOSURE_MANUAL)))
    exp = int(os.environ.get("VIDEO_EXPOSURE_TIME", str(EXPOSURE_TIME_30FPS)))
    dyn = int(os.environ.get("VIDEO_EXPOSURE_DYNAMIC", "0"))
    return ae, exp, dyn


def pin_c920_exposure(device: str) -> None:
    ae, exp, dyn = pin_from_env()
    cmd = pin_cmd(device, auto_exposure=ae, exposure_time=exp, dynamic_framerate=dyn)
    try:
        r = subprocess.run(cmd, capture_output=True, text=True, timeout=5)
    except OSError as exc:
        log.warning("pin %s failed: %s", device, exc)
        return
    if r.returncode:
        log.warning("pin %s rc=%s %s", device, r.returncode, (r.stderr or "").strip())
        return
    log.info("pinned %s ae=%s time=%s dynfps=%s", device, ae, exp, dyn)


def pin_devices(devices: list[str]) -> None:
    for dev in devices:
        pin_c920_exposure(dev)