package netns

import (
	"fmt"
	"os"
	"runtime"
	"testing"

	"github.com/vishvananda/netlink"
	"github.com/vishvananda/netns"
)

var (
	testNamespaceLinkName = "lo"
	dummyLinkName         = "ens4"
	dummyMTU              = 1440
)

// creates a testing network namespace and returns the handle and teardown function
func NewTestingNetworkNamespace(t *testing.T) (netns.NsHandle, func()) {
	if os.Getuid() != 0 {
		t.Skip("networking test requires root privileges, ensure bazel sandbox strategy is set to linux-sandbox.")
	}
	runtime.LockOSThread()
	ns, err := netns.New()
	if err != nil {
		t.Fatal(err)
	}
	return ns, func() {
		ns.Close()
		runtime.UnlockOSThread()
	}
}

// Creates a dummy device bridge to loopback device
func CreateDummyLink() error {
	lo, err := netlink.LinkByName(testNamespaceLinkName)
	if err != nil {
		return err
	}

	la := netlink.NewLinkAttrs()
	la.Name = dummyLinkName
	la.MTU = dummyMTU
	bridge := &netlink.Bridge{LinkAttrs: la}
	bridge.ParentIndex = lo.Attrs().Index
	if err := netlink.LinkAdd(bridge); err != nil {
		return err
	}
	return netlink.LinkSetUp(bridge)
}

// Returns an up-to-date dummy link
func GetDummyLink() (netlink.Link, error) {
	return GetByName(dummyLinkName)
}

func GetByName(name string) (netlink.Link, error) {
	link, err := netlink.LinkByName(name)
	if err != nil {
		return nil, fmt.Errorf("error getting link %s: %w", name, err)
	}
	return link, nil
}