import base64
import ipaddress
import re

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

bp = Blueprint('action_apply_vpn', __name__)

_VIEW    = '/view/view_vpn'
_MTU_MIN = 576
_MTU_MAX = 9000


def _wg_vlan(core):
    return next((v for v in core.get('vlans', []) if v.get('is_vpn')), None)


def _wg_vlan_by_name(core, name):
    return next((v for v in core.get('vlans', []) if v.get('is_vpn') and v.get('name') == name), None)


def _find_peer_by_flat_idx(core, flat_idx):
    """Return (vlan, peer_list_index) by flat index across all VPN VLANs in order."""
    i = 0
    for vlan in core.get('vlans', []):
        if not vlan.get('is_vpn'):
            continue
        peers = vlan.get('peers', [])
        for j in range(len(peers)):
            if i == flat_idx:
                return vlan, j
            i += 1
    return None, None


def _wg_iface(vlan, core):
    """Return the WireGuard interface name (wg0, wg1, ...) for a VPN VLAN."""
    wg_vlans = [v for v in core.get('vlans', []) if v.get('is_vpn')]
    idx = next((i for i, v in enumerate(wg_vlans) if v is vlan), 0)
    return f'wg{idx}'


def _row_index():
    try:
        return int(request.form.get('row_index', ''))
    except (ValueError, TypeError):
        return None


def _hash_ok():
    if not verify_core_hash(request.form.get('config_hash', '')):
        flash('Configuration was modified by another session. Please refresh and try again.', 'error')
        return False
    return True


def _generate_wg_keypair():
    """Generate an X25519 keypair compatible with WireGuard. Returns (private_b64, public_b64)."""
    from cryptography.hazmat.primitives.asymmetric.x25519 import X25519PrivateKey
    from cryptography.hazmat.primitives.serialization import (
        Encoding, PublicFormat, PrivateFormat, NoEncryption,
    )
    private  = X25519PrivateKey.generate()
    priv_raw = private.private_bytes(Encoding.Raw, PrivateFormat.Raw, NoEncryption())
    pub_raw  = private.public_key().public_bytes(Encoding.Raw, PublicFormat.Raw)
    return base64.b64encode(priv_raw).decode(), base64.b64encode(pub_raw).decode()


def _server_pubkey(iface):
    """Read the server public key written by core.py --apply."""
    try:
        with open(f'{CONFIGS_DIR}/.wg-{iface}.pub') as f:
            return f.read().strip()
    except OSError:
        return None


def _build_client_conf(vlan, peer_name, peer_ip, private_key, server_pubkey):
    """Build WireGuard client .conf content."""
    info      = vlan.get('vpn_information', {})
    overrides = info.get('explicit_overrides', {})
    subnet    = vlan.get('subnet', '')
    mask      = vlan.get('subnet_mask', '')
    network   = ipaddress.IPv4Network(f'{subnet}/{mask}', strict=False)
    ident_ips = [s['ip'] for s in vlan.get('server_identities', []) if s.get('ip')]
    default   = str(min((ipaddress.IPv4Address(ip) for ip in ident_ips),
                        key=lambda x: x.packed[-1])) if ident_ips else str(next(network.hosts()))
    gateway   = overrides.get('gateway') or default
    dns       = overrides.get('dns_server') or gateway
    prefix    = network.prefixlen
    mtu       = overrides.get('mtu', '')
    endpoint  = info.get('server_endpoint', '')
    listen_port = info.get('listen_port', 51820)

    split_tunnel = next(
        (p.get('split_tunnel', False) for p in vlan.get('peers', []) if p.get('name') == peer_name),
        False
    )
    allowed_ips = f'{subnet}/{prefix}' if split_tunnel else '0.0.0.0/0'

    lines = [
        f'# Generated by {PRODUCT_DISPLAY_NAME}',
        '',
        '[Interface]',
        f'PrivateKey = {private_key}',
        f'Address = {peer_ip}/{prefix}',
        f'DNS = {dns}',
    ]
    if mtu:
        lines.append(f'MTU = {mtu}')
    lines += ['', '[Peer]', f'PublicKey = {server_pubkey}']
    if endpoint:
        lines.append(f'Endpoint = {endpoint}:{listen_port}')
    lines += [f'AllowedIPs = {allowed_ips}', 'PersistentKeepalive = 25', '']
    return '\n'.join(lines)


def _conf_response(vlan, peer_name, peer_ip, private_key):
    """Return a .conf file download response, or redirect with error if pubkey unavailable."""
    core  = load_core()
    iface = _wg_iface(vlan, core)
    server_pub = _server_pubkey(iface)
    if not server_pub:
        flash('Peer saved. Run sudo python3 ~/routlin/core.py --apply to generate the server '
              'public key, then regenerate this peer to download the client config.', 'warning')
        return redirect(_VIEW)
    conf = _build_client_conf(vlan, peer_name, peer_ip, private_key, server_pub)
    safe = re.sub(r'[^A-Za-z0-9_\-]', '_', peer_name)
    resp = make_response(conf)
    resp.headers['Content-Type']        = 'text/plain; charset=utf-8'
    resp.headers['Content-Disposition'] = f'attachment; filename="vpn-client-{safe}.conf"'
    return resp


@bp.route('/action/apply_vpn', methods=['POST'])
@require_level('administrator')
def apply_vpn():
    listen_port_raw = request.form.get('vpn_listen_port',    '').strip()
    server_endpoint = validate.domainname(request.form.get('vpn_server_endpoint', ''))
    domain          = validate.domainname(request.form.get('vpn_domain',          ''))
    dns_raw         = request.form.get('vpn_dns_server',     '').strip()
    mtu_raw         = request.form.get('vpn_mtu',            '').strip()

    if not listen_port_raw:
        flash('Listen port is required.', 'error')
        return redirect(_VIEW)
    listen_port = validate.int_range(listen_port_raw, 1, 65535)
    if listen_port is None:
        flash(f'"{listen_port_raw}" is not a valid port number (1-65535).', 'error')
        return redirect(_VIEW)

    dns_server = ''
    if dns_raw:
        dns_server = validate.ip(dns_raw)
        if not dns_server:
            flash(f'"{dns_raw}" is not a valid IP address for DNS server.', 'error')
            return redirect(_VIEW)

    mtu = None
    if mtu_raw:
        mtu = validate.int_range(mtu_raw, _MTU_MIN, _MTU_MAX)
        if mtu is None:
            flash(f'"{mtu_raw}" is not a valid MTU (must be {_MTU_MIN}-{_MTU_MAX}).', 'error')
            return redirect(_VIEW)

    if not _hash_ok():
        return redirect(_VIEW)

    core = load_core()
    vpn_vlan = _wg_vlan(core)
    if vpn_vlan is None:
        flash('No WireGuard VLAN found in configuration.', 'error')
        return redirect(_VIEW)

    for v in core.get('vlans', []):
        if v.get('is_vpn') and v is not vpn_vlan and v.get('vpn_information', {}).get('listen_port') == listen_port:
            flash(f'Listen port {listen_port} is already used by another VPN VLAN.', 'error')
            return redirect(_VIEW)

    info = vpn_vlan.setdefault('vpn_information', {})
    info['listen_port']     = listen_port
    info['server_endpoint'] = server_endpoint
    info['domain']          = domain

    overrides = info.setdefault('explicit_overrides', {})
    if dns_server:
        overrides['dns_server'] = dns_server
    else:
        overrides.pop('dns_server', None)
    if mtu is not None:
        overrides['mtu'] = mtu
    else:
        overrides.pop('mtu', None)

    errors = validate.validate_config(core)
    if errors:
        for msg in errors:
            flash(msg, 'error')
        return redirect(_VIEW)
    save_core(core)
    flash(queued_msg('core apply'), 'success')
    return redirect(_VIEW)


@bp.route('/action/add_vpn_peer', methods=['POST'])
@require_level('administrator')
def add_vpn_peer():
    peer_name    = sanitize.name(request.form.get('peer_name', ''))
    peer_vlan_nm = request.form.get('peer_vlan', '').strip()
    peer_ip_raw  = request.form.get('peer_ip', '').strip()
    split_tunnel = 'split_tunnel' in request.form
    enabled      = 'enabled' in request.form

    if not peer_name:
        flash('Peer name is required.', 'error')
        return redirect(_VIEW)
    if not peer_vlan_nm:
        flash('Assigned VLAN is required.', 'error')
        return redirect(_VIEW)
    peer_ip = validate.ip(peer_ip_raw)
    if not peer_ip:
        flash(f'"{peer_ip_raw}" is not a valid IP address.', 'error')
        return redirect(_VIEW)

    if not _hash_ok():
        return redirect(_VIEW)

    core = load_core()
    vpn_vlan = _wg_vlan_by_name(core, peer_vlan_nm)
    if vpn_vlan is None:
        flash(f'VPN VLAN "{peer_vlan_nm}" not found.', 'error')
        return redirect(_VIEW)

    try:
        network = ipaddress.IPv4Network(f"{vpn_vlan['subnet']}/{vpn_vlan['subnet_mask']}", strict=False)
        if ipaddress.IPv4Address(peer_ip) not in network:
            flash(f'{peer_ip} is not within the subnet {vpn_vlan["subnet"]}/{vpn_vlan["subnet_mask"]} of {peer_vlan_nm}.', 'error')
            return redirect(_VIEW)
    except Exception:
        pass

    peers = vpn_vlan.setdefault('peers', [])
    if any(p.get('name') == peer_name for p in peers):
        flash(f'A peer named "{peer_name}" already exists.', 'error')
        return redirect(_VIEW)
    for v in core.get('vlans', []):
        if not v.get('is_vpn'):
            continue
        if any(p.get('ip') == peer_ip for p in v.get('peers', [])):
            flash(f'IP address {peer_ip} is already assigned to another peer.', 'error')
            return redirect(_VIEW)

    private_key, public_key = _generate_wg_keypair()
    peers.append({
        'name':         peer_name,
        'ip':           peer_ip,
        'public_key':   public_key,
        'split_tunnel': split_tunnel,
        'enabled':      enabled,
    })
    errors = validate.validate_config(core)
    if errors:
        for msg in errors:
            flash(msg, 'error')
        return redirect(_VIEW)
    save_core(core)

    return _conf_response(vpn_vlan, peer_name, peer_ip, private_key)


@bp.route('/action/edit_vpn_peer', methods=['POST'])
@require_level('administrator')
def edit_vpn_peer():
    flat_idx = _row_index()
    if flat_idx is None:
        flash('Invalid request.', 'error')
        return redirect(_VIEW)

    peer_name    = sanitize.name(request.form.get('name', ''))
    split_tunnel = request.form.get('split_tunnel') in ('true', '1', 'on', 'yes')
    enabled      = request.form.get('enabled') not in ('false', '0', '')

    if not peer_name:
        flash('Peer name is required.', 'error')
        return redirect(_VIEW)
    if not _hash_ok():
        return redirect(_VIEW)

    core = load_core()
    vlan, peer_idx = _find_peer_by_flat_idx(core, flat_idx)
    if vlan is None:
        flash('Peer not found.', 'error')
        return redirect(_VIEW)

    peers = vlan.get('peers', [])
    if any(j != peer_idx and p.get('name') == peer_name for j, p in enumerate(peers)):
        flash(f'A peer named "{peer_name}" already exists.', 'error')
        return redirect(_VIEW)

    peers[peer_idx].update({'name': peer_name, 'split_tunnel': split_tunnel, 'enabled': enabled})
    errors = validate.validate_config(core)
    if errors:
        for msg in errors:
            flash(msg, 'error')
        return redirect(_VIEW)
    save_core(core)
    flash(queued_msg('core apply'), 'success')
    return redirect(_VIEW)


@bp.route('/action/toggle_vpn_peer', methods=['POST'])
@require_level('administrator')
def toggle_vpn_peer():
    flat_idx = _row_index()
    if flat_idx is None:
        flash('Invalid request.', 'error')
        return redirect(_VIEW)
    if not _hash_ok():
        return redirect(_VIEW)

    core = load_core()
    vlan, peer_idx = _find_peer_by_flat_idx(core, flat_idx)
    if vlan is None:
        flash('Peer not found.', 'error')
        return redirect(_VIEW)

    peers = vlan.get('peers', [])
    peers[peer_idx]['enabled'] = not peers[peer_idx].get('enabled', True)
    errors = validate.validate_config(core)
    if errors:
        for msg in errors:
            flash(msg, 'error')
        return redirect(_VIEW)
    save_core(core)
    flash(queued_msg('core apply'), 'success')
    return redirect(_VIEW)


@bp.route('/action/delete_vpn_peer', methods=['POST'])
@require_level('administrator')
def delete_vpn_peer():
    flat_idx = _row_index()
    if flat_idx is None:
        flash('Invalid request.', 'error')
        return redirect(_VIEW)
    if not _hash_ok():
        return redirect(_VIEW)

    core = load_core()
    vlan, peer_idx = _find_peer_by_flat_idx(core, flat_idx)
    if vlan is None:
        flash('Peer not found.', 'error')
        return redirect(_VIEW)

    vlan.get('peers', []).pop(peer_idx)
    errors = validate.validate_config(core)
    if errors:
        for msg in errors:
            flash(msg, 'error')
        return redirect(_VIEW)
    save_core(core)
    flash(queued_msg('core apply'), 'success')
    return redirect(_VIEW)


@bp.route('/action/regenerate_vpn_peer', methods=['POST'])
@require_level('administrator')
def regenerate_vpn_peer():
    flat_idx = _row_index()
    if flat_idx is None:
        flash('Invalid request.', 'error')
        return redirect(_VIEW)
    if not _hash_ok():
        return redirect(_VIEW)

    core = load_core()
    vlan, peer_idx = _find_peer_by_flat_idx(core, flat_idx)
    if vlan is None:
        flash('Peer not found.', 'error')
        return redirect(_VIEW)

    private_key, public_key = _generate_wg_keypair()
    peer = vlan['peers'][peer_idx]
    peer['public_key'] = public_key
    errors = validate.validate_config(core)
    if errors:
        for msg in errors:
            flash(msg, 'error')
        return redirect(_VIEW)
    save_core(core)

    return _conf_response(vlan, peer['name'], peer['ip'], private_key)