package indexpointers

import (
	"bytes"
	"context"
	"errors"
	"io"
	"testing"
	"time"

	"github.com/stretchr/testify/require"

	"github.com/grafana/loki/v3/pkg/dataobj"
)

var indexPointerTestData = []IndexPointer{
	{Path: "/path/to/index/object/1", StartTs: unixTime(10), EndTs: unixTime(20)},
	{Path: "/path/to/index/object/2", StartTs: unixTime(12), EndTs: unixTime(17)},
	{Path: "/path/to/index/object/3", StartTs: unixTime(13), EndTs: unixTime(18)},
}

func unixTime(sec int64) time.Time { return time.Unix(sec, 0) }

func TestRowReader(t *testing.T) {
	dec := buildIndexPointersDecoder(t, 100) // Many pages
	r := NewRowReader(dec)
	actual, err := readAllIndexPointers(context.Background(), r)
	require.NoError(t, err)
	require.Equal(t, indexPointerTestData, actual)
}

func buildIndexPointersDecoder(t *testing.T, pageSize int) *Section {
	t.Helper()

	s := NewBuilder(nil, pageSize)
	for _, d := range indexPointerTestData {
		s.Append(d.Path, d.StartTs, d.EndTs)
	}

	var buf bytes.Buffer

	builder := dataobj.NewBuilder()
	require.NoError(t, builder.Append(s))

	_, err := builder.Flush(&buf)
	require.NoError(t, err)

	obj, err := dataobj.FromReaderAt(bytes.NewReader(buf.Bytes()), int64(buf.Len()))
	require.NoError(t, err)

	sec, err := Open(t.Context(), obj.Sections()[0])
	require.NoError(t, err)
	return sec
}

func readAllIndexPointers(ctx context.Context, r *RowReader) ([]IndexPointer, error) {
	var (
		res []IndexPointer
		buf = make([]IndexPointer, 128)
	)

	for {
		n, err := r.Read(ctx, buf)
		if n > 0 {
			res = append(res, buf[:n]...)
		}
		if errors.Is(err, io.EOF) {
			return res, nil
		} else if err != nil {
			return res, err
		}

		clear(buf)
	}
}