#!/usr/bin/python3
"""
Set system timezone

Set the system's timezone to `zone`, which should be a valid time zone
identifier from the tz database - like "America/New York" or "Europe/Berlin".

Removes `/etc/localtime`, then runs the host's `systemd-firstboot` binary with
the `--timezone` option, which will re-create `/etc/localtime`.
"""


import json
import subprocess
import sys
import os

SCHEMA = """
"additionalProperties": false,
"required": ["zone"],
"properties": {
  "zone": {
    "type": "string",
    "description": "Timezone identifier (from tzdb/zoneinfo)"
  }
}
"""

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

    # We need to remove the /etc/localtime symlink first, because it is created while we install RPM packages.
    # systemd-firstboot expects that if /etc/localtime exists it is a user-defined value and does not change it, but
    # the assumption is wrong, because it contains a default value from RPM package.
    # This is (hopefully) a temporary workaround.
    try:
        os.remove(f"{tree}/etc/localtime")
        # ^ This will fail once systemd RPM package stops shipping the file
        print("/etc/localtime already exists. Replacing.")
    except FileNotFoundError:
        pass

    subprocess.run(["systemd-firstboot", f"--root={tree}", f"--timezone={zone}"], check=True)

    return 0


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