#!/usr/bin/env python3
"""
Update the cell's DDNS record with the current public IP.

Called by: make ddns-update
           systemd timer (optional, see scripts/pic-ddns-update.timer)

Reads the DDNS token from data/api/.ddns_token (written by setup_cell.py).
Exits 0 on success or if already up to date, non-zero on failure.
"""
import json
import os
import sys
import urllib.error
import urllib.request

DDNS_URL = os.environ.get('DDNS_URL', 'https://ddns.pic.ngo/api/v1')
ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
TOKEN_FILE = os.path.join(ROOT, 'data', 'api', '.ddns_token')
IP_CACHE_FILE = os.path.join(ROOT, 'data', 'api', '.ddns_last_ip')


def get_public_ip() -> str:
    return urllib.request.urlopen('https://api.ipify.org', timeout=5).read().decode().strip()


def read_token() -> str:
    if not os.path.exists(TOKEN_FILE):
        print('ERROR: DDNS token not found. Run "make setup" to register.', file=sys.stderr)
        sys.exit(1)
    return open(TOKEN_FILE).read().strip()


def read_last_ip() -> str:
    try:
        return open(IP_CACHE_FILE).read().strip()
    except FileNotFoundError:
        return ''


def write_last_ip(ip: str) -> None:
    with open(IP_CACHE_FILE, 'w') as f:
        f.write(ip)


def main() -> int:
    try:
        public_ip = get_public_ip()
    except Exception as e:
        print(f'ERROR: Could not detect public IP: {e}', file=sys.stderr)
        return 1

    last_ip = read_last_ip()
    if public_ip == last_ip:
        print(f'DDNS: IP unchanged ({public_ip}) — no update needed')
        return 0

    token = read_token()
    data = json.dumps({'token': token, 'ip': public_ip}).encode()
    req = urllib.request.Request(
        f'{DDNS_URL}/update',
        data=data,
        headers={'Content-Type': 'application/json'},
        method='PUT',
    )
    try:
        resp = urllib.request.urlopen(req, timeout=10)
        result = json.loads(resp.read())
        if result.get('updated'):
            write_last_ip(public_ip)
            print(f'DDNS: Updated to {public_ip}')
            return 0
        else:
            print(f'ERROR: Unexpected response: {result}', file=sys.stderr)
            return 1
    except urllib.error.HTTPError as e:
        body = e.read().decode()
        print(f'ERROR: DDNS update failed ({e.code}): {body}', file=sys.stderr)
        return 1
    except Exception as e:
        print(f'ERROR: DDNS update failed: {e}', file=sys.stderr)
        return 1


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