package link

import (
	"errors"
	"math"
	"os"
	"path/filepath"
	"reflect"
	"testing"

	"github.com/cilium/ebpf"
	"github.com/cilium/ebpf/asm"
	"github.com/cilium/ebpf/internal/testutils"
	"github.com/cilium/ebpf/internal/unix"
)

func TestRawLink(t *testing.T) {
	cgroup, prog := mustCgroupFixtures(t)

	link, err := AttachRawLink(RawLinkOptions{
		Target:  int(cgroup.Fd()),
		Program: prog,
		Attach:  ebpf.AttachCGroupInetEgress,
	})
	testutils.SkipIfNotSupported(t, err)
	if err != nil {
		t.Fatal("Can't create raw link:", err)
	}

	info, err := link.Info()
	if err != nil {
		t.Fatal("Can't get link info:", err)
	}

	pi, err := prog.Info()
	if err != nil {
		t.Fatal("Can't get program info:", err)
	}

	progID, ok := pi.ID()
	if !ok {
		t.Fatal("Program ID not available in program info")
	}

	if info.Program != progID {
		t.Error("Link program ID doesn't match program ID")
	}

	testLink(t, link, testLinkOptions{
		prog: prog,
		loadPinned: func(f string, opts *ebpf.LoadPinOptions) (Link, error) {
			return LoadPinnedRawLink(f, UnspecifiedType, opts)
		},
	})
}

func TestRawLinkLoadPinnedWithOptions(t *testing.T) {
	cgroup, prog := mustCgroupFixtures(t)

	link, err := AttachRawLink(RawLinkOptions{
		Target:  int(cgroup.Fd()),
		Program: prog,
		Attach:  ebpf.AttachCGroupInetEgress,
	})
	testutils.SkipIfNotSupported(t, err)
	if err != nil {
		t.Fatal("Can't create raw link:", err)
	}

	path := filepath.Join(testutils.TempBPFFS(t), "link")
	err = link.Pin(path)
	testutils.SkipIfNotSupported(t, err)
	if err != nil {
		t.Fatal(err)
	}

	// It seems like the kernel ignores BPF_F_RDONLY when updating a link,
	// so we can't test this.
	_, err = LoadPinnedRawLink(path, UnspecifiedType, &ebpf.LoadPinOptions{
		Flags: math.MaxUint32,
	})
	if !errors.Is(err, unix.EINVAL) {
		t.Fatal("Invalid flags don't trigger an error:", err)
	}
}

func mustCgroupFixtures(t *testing.T) (*os.File, *ebpf.Program) {
	t.Helper()

	testutils.SkipIfNotSupported(t, haveProgAttach())

	return testutils.CreateCgroup(t), mustCgroupEgressProgram(t)
}

func mustCgroupEgressProgram(t *testing.T) *ebpf.Program {
	t.Helper()

	prog, err := ebpf.NewProgram(&ebpf.ProgramSpec{
		Type:       ebpf.CGroupSKB,
		AttachType: ebpf.AttachCGroupInetEgress,
		License:    "MIT",
		Instructions: asm.Instructions{
			asm.Mov.Imm(asm.R0, 0),
			asm.Return(),
		},
	})
	if err != nil {
		t.Fatal(err)
	}

	t.Cleanup(func() {
		prog.Close()
	})

	return prog
}

type testLinkOptions struct {
	prog       *ebpf.Program
	loadPinned func(string, *ebpf.LoadPinOptions) (Link, error)
}

func testLink(t *testing.T, link Link, opts testLinkOptions) {
	t.Helper()

	tmp, err := os.MkdirTemp("/sys/fs/bpf", "ebpf-test")
	if err != nil {
		t.Fatal(err)
	}
	defer os.RemoveAll(tmp)

	path := filepath.Join(tmp, "link")
	err = link.Pin(path)
	if err == ErrNotSupported {
		t.Errorf("%T.Pin returns unwrapped ErrNotSupported", link)
	}

	if opts.loadPinned == nil {
		if !errors.Is(err, ErrNotSupported) {
			t.Errorf("%T.Pin doesn't return ErrNotSupported: %s", link, err)
		}
	} else {
		if err != nil {
			t.Fatalf("Can't pin %T: %s", link, err)
		}

		link2, err := opts.loadPinned(path, nil)
		if err != nil {
			t.Fatalf("Can't load pinned %T: %s", link, err)
		}
		link2.Close()

		if reflect.TypeOf(link) != reflect.TypeOf(link2) {
			t.Errorf("Loading a pinned %T returns a %T", link, link2)
		}

		_, err = opts.loadPinned(path, &ebpf.LoadPinOptions{
			Flags: math.MaxUint32,
		})
		if !errors.Is(err, unix.EINVAL) {
			t.Errorf("Loading a pinned %T doesn't respect flags", link)
		}
	}

	t.Run("update", func(t *testing.T) {
		err := link.Update(opts.prog)
		if err == ErrNotSupported {
			t.Fatal("Update returns unwrapped ErrNotSupported", link)
		}
		if errors.Is(err, ErrNotSupported) {
			return
		}
		if err != nil {
			t.Fatal("Update returns an error:", err)
		}

		func() {
			// Panicking is OK
			defer func() {
				_ = recover()
			}()

			if err := link.Update(nil); err == nil {
				t.Fatalf("%T.Update accepts nil program", link)
			}
		}()
	})

	if err := link.Close(); err != nil {
		t.Fatalf("%T.Close returns an error: %s", link, err)
	}
}