from flask import Blueprint, request, redirect, flash
from auth import require_level
from config_utils import load_core, save_core, verify_core_hash, apply_msg
import sanitize

bp = Blueprint('action_apply_upstream_dns', __name__)



@bp.route('/action/apply_upstream_dns', methods=['POST'])
@require_level('administrator')
def apply_upstream_dns():
    strict_order     = 'strict_order' in request.form
    cache_size_raw   = request.form.get('cache_size', '').strip()
    upstream_servers = [sanitize.ip(s) for s in request.form.getlist('upstream_servers') if s.strip()]
    upstream_servers = [s for s in upstream_servers if s]

    try:
        cache_size = int(cache_size_raw)
        if cache_size < 0:
            raise ValueError
    except (ValueError, TypeError):
        flash('Cache Size must be a non-negative integer.', 'error')
        return redirect('/view/view_upstream_dns')

    if not verify_core_hash(request.form.get('config_hash', '')):
        flash('Configuration was modified by another session. Please refresh and try again.', 'error')
        return redirect('/view/view_upstream_dns')

    core = load_core()
    core.setdefault('upstream_dns', {}).update({
        'strict_order':    strict_order,
        'cache_size':      cache_size,
        'upstream_servers': upstream_servers,
    })
    save_core(core)

    flash(apply_msg(), 'success')
    return redirect('/view/view_upstream_dns')