Write local events and release the camera

"""Use a V4L2/OpenCV camera or a local image; never follow decoded URLs."""
import argparse
from datetime import datetime, timezone
import json
from pathlib import Path
import time
from journal import Journal


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--device", type=int, default=0)
    parser.add_argument("--image", type=Path)
    parser.add_argument("--output", type=Path, default=Path("events.jsonl"))
    args = parser.parse_args()
    import cv2  # Install python3-opencv using your OS package manager.
    detector, journal = cv2.QRCodeDetector(), Journal()
    camera = None
    try:
        if not args.image:
            camera = cv2.VideoCapture(args.device)
            if not camera.isOpened():
                raise RuntimeError("Camera unavailable; verify its vendor example and device index first")
        with args.output.open("a", encoding="utf-8") as log:
            while True:
                if args.image:
                    frame = cv2.imread(str(args.image))
                    ok = frame is not None
                else:
                    ok, frame = camera.read()
                if not ok:
                    raise RuntimeError("No image/frame; no event was recorded")
                payload, _, _ = detector.detectAndDecode(frame)
                event = journal.accept(payload, time.monotonic())
                if event:
                    event["at_utc"] = datetime.now(timezone.utc).isoformat()
                    log.write(json.dumps(event, ensure_ascii=True) + "\n")
                    log.flush()
                    print(event["label"])
                if args.image:
                    break
                time.sleep(0.05)
    except KeyboardInterrupt:
        pass
    finally:
        if camera:
            camera.release()


if __name__ == "__main__":
    main()