from flask import Blueprint, request, redirect, flash
from auth import require_level
from config_utils import load_core, save_core, verify_core_hash, queued_msg
import sanitize
import validation as validate

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()
    submitted      = request.form.getlist('upstream_servers')

    for s in submitted:
        if not s.strip():
            flash('Remove blank server entries before saving.', 'error')
            return redirect('/view/view_upstream_dns')

    upstream_servers = []
    for s in submitted:
        clean = sanitize.ip(s.strip())
        if not clean:
            flash(f"'{s.strip()}' is not a valid IP address.", 'error')
            return redirect('/view/view_upstream_dns')
        upstream_servers.append(clean)

    cache_size = validate.int_range(cache_size_raw, 0, None)
    if cache_size is None:
        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()
    current     = core.get('upstream_dns', {})
    if (strict_order      == bool(current.get('strict_order', False)) and
            cache_size    == int(current.get('cache_size', 0)) and
            upstream_servers == current.get('upstream_servers', [])):
        flash('No changes detected.', 'info')
        return redirect('/view/view_upstream_dns')

    core.setdefault('upstream_dns', {}).update({
        'strict_order':     strict_order,
        'cache_size':       cache_size,
        'upstream_servers': upstream_servers,
    })
    errors = validate.validate_config(core)
    if errors:
        for msg in errors:
            flash(msg, 'error')
        return redirect('/view/view_upstream_dns')
    save_core(core)
    flash(queued_msg('core apply'), 'success')
    return redirect('/view/view_upstream_dns')