"""Private launch barrier for sdk.run_process; stdlib-only under Python -I."""

import json
import os
from pathlib import Path
import signal
import subprocess
import sys
import threading
import time


def watch_parent(expected: int):
    while True:
        if os.getppid() != expected:
            os.killpg(os.getpid(), signal.SIGKILL)
        time.sleep(0.1)


def main():
    status = Path(sys.argv[1])
    if os.name != "nt":
        threading.Thread(target=watch_parent, args=(int(sys.argv[2]),), daemon=True).start()
    # Until the parent owns our job/session and sends this line, no business
    # process can start. Buffering is local; tool stdin uses a separate pipe.
    control = sys.stdin.buffer.readline(1024 * 1024 + 1)
    if not control.endswith(b"\n") or len(control) > 1024 * 1024:
        return
    request = json.loads(control)
    size = request["input_size"]
    if type(size) is not int or not 0 <= size <= 64 * 1024 * 1024:
        return
    content = sys.stdin.buffer.read(size) if request["has_input"] else None
    if content is not None and len(content) != size:
        return
    try:
        result = subprocess.run(
            request["argv"],
            shell=False,
            stdin=None if request["has_input"] else subprocess.DEVNULL,
            input=content,
            creationflags=subprocess.CREATE_NO_WINDOW if os.name == "nt" else 0,
            check=False,
        )
        response = {"returncode": result.returncode}
    except OSError:
        response = {"launch_failed": True}
    pending = status.with_suffix(".tmp")
    pending.write_text(json.dumps(response), encoding="utf-8")
    pending.replace(status)
    # Remain the session/group leader until the owner reclaims the whole tree.
    while True:
        time.sleep(60)


if __name__ == "__main__":
    main()