//go:build linux && !android && !e2e_testing
// +build linux,!android,!e2e_testing

package tio

import (
	"errors"
	"os"
	"sync"
	"testing"
	"time"

	"github.com/slackhq/nebula/wire"
	"github.com/stretchr/testify/require"
	"golang.org/x/sys/unix"
)

// newReadPipe returns a read fd. The matching write fd is registered for cleanup.
// The caller takes ownership of the read fd (pass it into a QueueSet).
func newReadPipe(t *testing.T) int {
	t.Helper()
	var fds [2]int
	if err := unix.Pipe2(fds[:], unix.O_CLOEXEC); err != nil {
		t.Fatalf("pipe2: %v", err)
	}
	t.Cleanup(func() { _ = unix.Close(fds[1]) })
	return fds[0]
}

func TestPoll_WakeForShutdown_WakesFriends(t *testing.T) {
	parent, err := NewPollQueueSet()
	require.NoError(t, err)
	require.NoError(t, parent.Add(newReadPipe(t)))
	require.NoError(t, parent.Add(newReadPipe(t)))
	// QueueSet.Close owns the read fds we Added — don't register a separate
	// Cleanup to close them or we'll double-close whatever fd the kernel
	// has since reused.

	readers := parent.Queues()
	errs := make([]error, len(readers))
	var wg sync.WaitGroup
	for i, r := range readers {
		wg.Add(1)
		go func(i int, r Queue) {
			defer wg.Done()
			pkts := make([]wire.TunPacket, 1)
			_, errs[i] = r.Read(pkts, make([]byte, 64))
		}(i, r)
	}

	time.Sleep(50 * time.Millisecond)

	if err := parent.Close(); err != nil {
		t.Fatalf("Close: %v", err)
	}

	done := make(chan struct{})
	go func() { wg.Wait(); close(done) }()
	select {
	case <-done:
	case <-time.After(2 * time.Second):
		t.Fatal("readers did not wake")
	}

	for i, err := range errs {
		if !errors.Is(err, os.ErrClosed) {
			t.Errorf("reader %d: expected os.ErrClosed, got %v", i, err)
		}
	}
}

func TestPoll_Close_Idempotent(t *testing.T) {
	shutdownFd, err := unix.Eventfd(0, unix.EFD_NONBLOCK|unix.EFD_CLOEXEC)
	require.NoError(t, err)
	t.Cleanup(func() { _ = unix.Close(shutdownFd) })

	tf, err := newPoll(newReadPipe(t), shutdownFd)
	require.NoError(t, err)
	if err := tf.Close(); err != nil {
		t.Fatalf("first Close: %v", err)
	}
	if err := tf.Close(); err != nil {
		t.Fatalf("second Close should be a no-op, got %v", err)
	}
}

func TestPollQueueSet_Close_ClosesEventfd(t *testing.T) {
	qs, err := NewPollQueueSet()
	require.NoError(t, err)
	require.NoError(t, qs.Add(newReadPipe(t)))

	fd := qs.(*pollQueueSet).shutdownFd
	require.NoError(t, qs.Close())

	// Closing the eventfd again should fail with EBADF, proving Close
	// actually released it.
	if err := unix.Close(fd); err == nil {
		t.Fatalf("eventfd %d still open after QueueSet.Close", fd)
	}

	// Second Close must be a no-op (and must not double-close the eventfd
	// in case the kernel handed it out to another caller in the meantime).
	if err := qs.Close(); err != nil {
		t.Fatalf("second Close: %v", err)
	}
}