//go:build linux && !android

package device

import (
	"fmt"
	"net"
	"net/netip"
	"os"

	log "github.com/sirupsen/logrus"
	"github.com/vishvananda/netlink"

	"github.com/netbirdio/netbird/client/iface/wgaddr"
)

type wgLink struct {
	attrs *netlink.LinkAttrs
}

func newWGLink(name string) *wgLink {
	attrs := netlink.NewLinkAttrs()
	attrs.Name = name

	return &wgLink{
		attrs: &attrs,
	}
}

// Attrs returns the Wireguard's default attributes
func (l *wgLink) Attrs() *netlink.LinkAttrs {
	return l.attrs
}

// Type returns the interface type
func (l *wgLink) Type() string {
	return "wireguard"
}

// Close deletes the link interface
func (l *wgLink) Close() error {
	return netlink.LinkDel(l)
}

func (l *wgLink) recreate() error {
	name := l.attrs.Name

	// check if interface exists
	link, err := netlink.LinkByName(name)
	if err != nil {
		switch err.(type) {
		case netlink.LinkNotFoundError:
			break
		default:
			return fmt.Errorf("link by name: %w", err)
		}
	}

	// remove if interface exists
	if link != nil {
		err = netlink.LinkDel(l)
		if err != nil {
			return err
		}
	}

	log.Debugf("adding device: %s", name)
	err = netlink.LinkAdd(l)
	if os.IsExist(err) {
		log.Infof("interface %s already exists. Will reuse.", name)
	} else if err != nil {
		return fmt.Errorf("link add: %w", err)
	}

	return nil
}

func (l *wgLink) setMTU(mtu int) error {
	if err := netlink.LinkSetMTU(l, mtu); err != nil {
		log.Errorf("error setting MTU on interface: %s", l.attrs.Name)

		return fmt.Errorf("link set mtu: %w", err)
	}

	return nil
}

func (l *wgLink) up() error {
	if err := netlink.LinkSetUp(l); err != nil {
		log.Errorf("error bringing up interface: %s", l.attrs.Name)
		return fmt.Errorf("link setup: %w", err)
	}

	return nil
}

func (l *wgLink) assignAddr(address *wgaddr.Address) error {
	//delete existing addresses
	list, err := netlink.AddrList(l, 0)
	if err != nil {
		return fmt.Errorf("list addr: %w", err)
	}

	if len(list) > 0 {
		for _, a := range list {
			addr := a
			err = netlink.AddrDel(l, &addr)
			if err != nil {
				return fmt.Errorf("del addr: %w", err)
			}
		}
	}

	name := l.attrs.Name

	if err := l.addAddr(name, address.Prefix()); err != nil {
		return err
	}

	if address.HasIPv6() {
		if err := l.addAddr(name, address.IPv6Prefix()); err != nil {
			log.Warnf("failed to assign IPv6 address %s to %s, continuing v4-only: %v", address.IPv6Prefix(), name, err)
			address.ClearIPv6()
		}
	}

	// On linux, the link must be brought up
	if err := netlink.LinkSetUp(l); err != nil {
		return fmt.Errorf("link setup: %w", err)
	}

	return nil
}

func (l *wgLink) addAddr(ifaceName string, prefix netip.Prefix) error {
	log.Debugf("adding address %s to interface: %s", prefix, ifaceName)

	addr := &netlink.Addr{
		IPNet: &net.IPNet{
			IP:   prefix.Addr().AsSlice(),
			Mask: net.CIDRMask(prefix.Bits(), prefix.Addr().BitLen()),
		},
	}

	if err := netlink.AddrAdd(l, addr); os.IsExist(err) {
		log.Infof("interface %s already has the address: %s", ifaceName, prefix)
	} else if err != nil {
		return fmt.Errorf("add addr %s: %w", prefix, err)
	}

	return nil
}