#!/usr/bin/env python3
"""
Add crossmnt to TrueNAS NFS exports for child dataset visibility.

Usage: fix-nfs-crossmnt.py /mnt/pool/dataset

Setup:
  1. scp fix-nfs-crossmnt.py root@truenas.local:/root/
  2. chmod +x /root/fix-nfs-crossmnt.py
  3. Test: /root/fix-nfs-crossmnt.py /mnt/pool/dataset
  4. Add cron job: TrueNAS UI > System > Advanced > Cron Jobs
     Command: /root/fix-nfs-crossmnt.py /mnt/pool/dataset
     Schedule: */5 * * * *
"""

import re
import subprocess
import sys
from pathlib import Path

EXPORTS_FILE = Path("/etc/exports")


def main():
    if len(sys.argv) != 2:
        print(f"Usage: {sys.argv[0]} /mnt/pool/dataset", file=sys.stderr)
        return 1

    export_path = sys.argv[1]
    content = EXPORTS_FILE.read_text()

    if f'"{export_path}"' not in content:
        print(f"ERROR: {export_path} not found in {EXPORTS_FILE}", file=sys.stderr)
        return 1

    lines = content.splitlines()
    result = []
    in_block = False
    modified = False

    for line in lines:
        if f'"{export_path}"' in line:
            in_block = True
        elif line.startswith('"'):
            in_block = False

        if in_block and line[:1] in (" ", "\t") and "crossmnt" not in line:
            line = re.sub(r"\)(\\\s*)?$", r",crossmnt)\1", line)
            modified = True

        result.append(line)

    if not modified:
        return 0  # Already applied

    EXPORTS_FILE.write_text("\n".join(result) + "\n")
    subprocess.run(["exportfs", "-ra"], check=True)
    print(f"Added crossmnt to {export_path}")
    return 0


if __name__ == "__main__":
    sys.exit(main())