# Allows a mentor to ssh into a DigitalOcean droplet. This is designed to be
# executed on the target machine.
#
# This script takes the username of the mentor as an argument:
#
# $ python3 add_mentor.py <mentor's username>
#
# Alternatively you can pass in --remove to remove their SSH key from the
# machine:
#
# $ python3 add_mentor.py --remove <mentor's username>
import os
import re
import socket
import sys
from argparse import ArgumentParser
from typing import List

import requests

parser = ArgumentParser(description="Give a mentor ssh access to this machine.")
parser.add_argument("username", help="GitHub username of the mentor.")
parser.add_argument("--remove", help="Remove his/her key from the machine.", action="store_true")

# Wrap keys with line comments for easier key removal.
append_key = """\
#<{username}>{{{{
{key}
#}}}}<{username}>
"""


def get_mentor_keys(username: str) -> List[str]:
    url = f"https://api.github.com/users/{username}/keys"

    r = requests.get(url)
    if r.status_code != 200:
        print("Cannot connect to GitHub...")
        sys.exit(1)

    keys = r.json()
    if not keys:
        print(f'Mentor "{username}" has no public key.')
        sys.exit(1)

    return [key["key"] for key in keys]


if __name__ == "__main__":
    args = parser.parse_args()
    authorized_keys = os.path.expanduser("~/.ssh/authorized_keys")

    if args.remove:
        remove_re = re.compile(
            "#<{0}>{{{{.+}}}}<{0}>(\n)?".format(args.username), re.DOTALL | re.MULTILINE
        )

        with open(authorized_keys, "r+") as f:
            old_content = f.read()
            new_content = re.sub(remove_re, "", old_content)
            f.seek(0)
            f.write(new_content)
            f.truncate()

        print(f"Successfully removed {args.username}' SSH key!")

    else:
        keys = get_mentor_keys(args.username)
        with open(authorized_keys, "a") as f:
            for key in keys:
                f.write(append_key.format(username=args.username, key=key))

        print(f"Successfully added {args.username}'s SSH key!")
        print("Can you let your mentor know that they can connect to this machine with:\n")
        print(f"    $ ssh zulipdev@{socket.gethostname()}\n")