package tablewatch

import (
	"encoding/binary"
	"testing"

	"golang.org/x/sys/unix"
)

// msg is a netlink message of a type, with a few bytes of payload.
func msg(typ uint16) []byte {
	b := make([]byte, unix.NLMSG_HDRLEN+4)
	binary.NativeEndian.PutUint32(b[0:4], uint32(len(b)))
	binary.NativeEndian.PutUint16(b[4:6], typ)
	return b
}

func TestDeletesTable(t *testing.T) {
	nft := func(m uint16) uint16 { return unix.NFNL_SUBSYS_NFTABLES<<8 | m }
	newRule, delTable, delChain := msg(nft(unix.NFT_MSG_NEWRULE)), msg(nft(unix.NFT_MSG_DELTABLE)), msg(nft(unix.NFT_MSG_DELCHAIN))
	cases := []struct {
		b    []byte
		want bool
	}{
		{delTable, true},
		{append(append([]byte{}, newRule...), delTable...), true},
		{append(append([]byte{}, newRule...), delChain...), false},
		{newRule, false},
		{delTable[:10], false},
		{nil, false},
	}
	for i, c := range cases {
		if got := DeletesTable(c.b); got != c.want {
			t.Errorf("%d: %v", i, got)
		}
	}
}