package ebpf_test

import (
	"errors"
	"testing"

	"github.com/cilium/ebpf"
)

var (
	keysMockCalled   int
	valuesMockCalled int
)

type keysMock []any

func (u keysMock) UnmarshalBinary(data []byte) error {
	keysMockCalled++
	return nil
}

type valuesMock []any

func (u valuesMock) UnmarshalBinary(data []byte) error {
	valuesMockCalled++
	return nil
}

func TestLastBatchUnmarshalValuesNotCalled(t *testing.T) {
	// Choose batch size in a way that last batch returns ErrKeyNotExist.
	var maxEntries, batchSize uint32 = 4, 3

	m, err := ebpf.NewMap(&ebpf.MapSpec{
		Type:       ebpf.Array,
		MaxEntries: maxEntries,
		KeySize:    4,
		ValueSize:  4,
	})
	if err != nil {
		t.Fatalf("create map: %v", err)
	}

	var (
		cursor    ebpf.MapBatchCursor
		keysOut   = make(keysMock, batchSize)
		valuesOut = make(valuesMock, batchSize)
	)

	_, err = m.BatchLookup(&cursor, keysOut, valuesOut, nil)
	if err != nil {
		t.Fatalf("first batch lookup failed: %v", err)
	}

	_, err = m.BatchLookup(&cursor, keysOut, valuesOut, nil)
	if !errors.Is(err, ebpf.ErrKeyNotExist) {
		t.Fatalf("second batch lookup must return ErrKeyNotExist, got %v", err)
	}

	if keysMockCalled != 2 {
		t.Errorf("keys mock calls: got %d, want %d", keysMockCalled, 2)
	}

	// This fails unexpectedly. It should be 2 (called for both batches), but
	// is 1 (not called for last batch).
	if valuesMockCalled != 2 {
		t.Errorf("values mock calls: got %d, want %d", valuesMockCalled, 2)
	}
}