#!/usr/bin/env python3
from __future__ import annotations
import os
import re
import sys
from pathlib import Path

STACK_DIR = Path(__file__).resolve().parent.parent
ENV_FILE = Path(os.environ.get('ENV_FILE', STACK_DIR / '.env'))
TEMPLATE = STACK_DIR / 'keepalived.conf.template'
OUTPUT = STACK_DIR / 'keepalived.conf'


def load_env(path: Path) -> dict[str, str]:
    env = dict(os.environ)
    if path.exists():
        for raw in path.read_text(encoding='utf-8').splitlines():
            line = raw.strip()
            if not line or line.startswith('#') or '=' not in line:
                continue
            k, v = line.split('=', 1)
            env.setdefault(k.strip(), v.strip().strip('"').strip("'"))
    return env


def main() -> int:
    env = load_env(ENV_FILE)
    required = [
        'LAN_INTERFACE', 'VIP_CIDR', 'KEEPALIVED_ROUTER_ID', 'KEEPALIVED_STATE',
        'KEEPALIVED_PRIORITY', 'KEEPALIVED_PASSWORD', 'PD_PIHOLE_WEB_PORT'
    ]
    missing = [k for k in required if not env.get(k)]
    if missing:
        print(f'Missing required vars in {ENV_FILE}: {", ".join(missing)}', file=sys.stderr)
        return 1

    keepalived_password = env['KEEPALIVED_PASSWORD']
    if len(keepalived_password) > 8:
        print('KEEPALIVED_PASSWORD must be 8 characters or fewer for VRRP PASS auth.', file=sys.stderr)
        return 1

    try:
        web_port_hex = f"{int(env['PD_PIHOLE_WEB_PORT']):04X}"
    except ValueError:
        print('PD_PIHOLE_WEB_PORT must be an integer.', file=sys.stderr)
        return 1

    router_id_name = f"pihole_{re.sub(r'[^a-z0-9]+', '_', env['KEEPALIVED_STATE'].lower())}"
    nopreempt_line = '    nopreempt' if env.get('KEEPALIVED_NOPREEMPT', 'true').lower() in {'1','true','yes','on'} else ''

    rendered = TEMPLATE.read_text(encoding='utf-8')
    replacements = {
        'ROUTER_ID_NAME': router_id_name,
        'PIHOLE_WEB_PORT_HEX': web_port_hex,
        'NOPREEMPT_LINE': nopreempt_line,
    }
    replacements.update({k: env[k] for k in required})
    for key, value in replacements.items():
        rendered = rendered.replace('${' + key + '}', value)

    OUTPUT.write_text(rendered.rstrip() + '\n', encoding='utf-8')
    print(f'Rendered {OUTPUT}')
    return 0


if __name__ == '__main__':
    raise SystemExit(main())