#!/usr/bin/python3
"""
Set up an early root shell on a certain tty

Creates a systemd unit file at /etc/systemd/system/osbuild-debug-shell.service
which starts an early-boot root shell on the given `tty`.

Also symlinks the service file into /etc/systemd/system/sysinit.target.wants/.
"""


import json
import os
import sys

SCHEMA = """
"additionalProperties": false,
"required": ["tty"],
"properties": {
  "tty": {
    "type": "string",
    "description": "Absolute path of the tty device to start a root shell on."
  }
}
"""


def main(tree, options):
    tty = options["tty"]

    unit = f"""
[Unit]
Description=Early root shell on {tty} FOR DEBUGGING ONLY
DefaultDependencies=no
IgnoreOnIsolate=yes
ConditionPathExists={tty}

[Service]
Environment=TERM=linux
ExecStart=/bin/sh
Restart=always
RestartSec=0
StandardInput=tty
TTYPath={tty}
TTYReset=yes
TTYVHangup=yes
KillMode=process
IgnoreSIGPIPE=no
# bash ignores SIGTERM
KillSignal=SIGHUP

# Unset locale for the console getty since the console has problems
# displaying some internationalized messages.
UnsetEnvironment=LANG LANGUAGE LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT LC_IDENTIFICATION
"""

    with open(f"{tree}/etc/systemd/system/osbuild-debug-shell.service", "w") as f:
        f.write(unit)

    os.symlink("../osbuild-debug-shell.service",
               f"{tree}/etc/systemd/system/sysinit.target.wants/osbuild-debug-shell.service")

    return 0


if __name__ == '__main__':
    args = json.load(sys.stdin)
    r = main(args["tree"], args["options"])
    sys.exit(r)