import re
import subprocess

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_interface', __name__)

_VIEW = '/view/view_general'


def _get_system_interfaces():
    try:
        r = subprocess.run(['ip', 'link', 'show'], capture_output=True, text=True, timeout=5)
        names = re.findall(r'^\d+:\s+(\S+):', r.stdout, re.MULTILINE)
        return {n.split('@')[0] for n in names} - {'lo'}
    except Exception:
        return set()


@bp.route('/action/apply_interface', methods=['POST'])
@require_level('administrator')
def apply_interface():
    idx_raw   = request.form.get('row_index', '').strip()
    interface = sanitize.interface_name(request.form.get('interface', ''))

    try:
        idx = int(idx_raw)
        if idx not in (0, 1):
            raise ValueError
    except (ValueError, TypeError):
        flash('Invalid request.', 'error')
        return redirect(_VIEW)

    if not interface:
        flash('Interface name is required.', 'error')
        return redirect(_VIEW)

    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)

    core = load_core()
    gen  = core.setdefault('general', {})

    other_key = 'lan_interface' if idx == 0 else 'wan_interface'
    if interface == gen.get(other_key, ''):
        flash('WAN and LAN interfaces must be different.', 'error')
        return redirect(_VIEW)

    available = _get_system_interfaces()
    if available and interface not in available:
        flash(f"Interface '{interface}' does not exist on this system.", 'error')
        return redirect(_VIEW)

    key = 'wan_interface' if idx == 0 else 'lan_interface'
    gen[key] = interface
    save_core(core)

    flash(apply_msg(), 'success')
    return redirect(_VIEW)