package queryrange

import (
	"context"
	"math"
	"testing"
	"time"

	"github.com/go-kit/log"
	"github.com/stretchr/testify/require"
	"github.com/weaveworks/common/user"

	"github.com/grafana/loki/pkg/logproto"
	"github.com/grafana/loki/pkg/logqlmodel/stats"
	"github.com/grafana/loki/pkg/querier/queryrange/queryrangebase"
	"github.com/grafana/loki/pkg/storage/chunk/cache"
	"github.com/grafana/loki/pkg/util"
)

func TestIndexStatsCache(t *testing.T) {
	cfg := queryrangebase.ResultsCacheConfig{
		CacheConfig: cache.Config{
			Cache: cache.NewMockCache(),
		},
	}
	c, err := cache.New(cfg.CacheConfig, nil, log.NewNopLogger(), stats.ResultCache)
	require.NoError(t, err)
	cacheMiddleware, err := NewIndexStatsCacheMiddleware(
		log.NewNopLogger(),
		WithSplitByLimits(fakeLimits{}, 24*time.Hour),
		LokiCodec,
		c,
		nil,
		nil,
		func(_ context.Context, tenantIDs []string, r queryrangebase.Request) int {
			return 1
		},
		false,
		nil,
		nil,
	)
	require.NoError(t, err)

	from, through := util.RoundToMilliseconds(testTime, testTime.Add(1*time.Hour))
	statsReq := &logproto.IndexStatsRequest{
		From:     from,
		Through:  through,
		Matchers: `{foo="bar"}`,
	}

	statsResp := &IndexStatsResponse{
		Response: &logproto.IndexStatsResponse{
			Streams: 1,
			Chunks:  2,
			Bytes:   1 << 10,
			Entries: 10,
		},
	}

	var calls int
	rc := cacheMiddleware.Wrap(queryrangebase.HandlerFunc(func(_ context.Context, req queryrangebase.Request) (queryrangebase.Response, error) {
		calls++
		return statsResp, nil
	}))

	ctx := user.InjectOrgID(context.Background(), "fake")
	resp, err := rc.Do(ctx, statsReq)
	require.NoError(t, err)
	require.Equal(t, 1, calls)
	require.Equal(t, statsResp, resp)

	// Doing same request again shouldn't change anything.
	calls = 0
	resp, err = rc.Do(ctx, statsReq)
	require.NoError(t, err)
	require.Equal(t, 0, calls)
	require.Equal(t, statsResp, resp)

	// Doing a request with new start later than the previous query and end time later than the previous one,
	// should reuse part of the previous request and issue a new request for the remaining time till end.
	// The new start time is 15m (i.e. 25%) in the future with regard to the previous request time span.
	calls = 0
	req := statsReq.WithStartEnd(statsReq.GetStart()+(15*time.Minute).Milliseconds(), statsReq.GetEnd()+(15*time.Minute).Milliseconds())
	expectedStats := &IndexStatsResponse{
		Response: &logproto.IndexStatsResponse{
			Streams: 2,
			Chunks:  4,
			Bytes:   (1<<10)*0.75 + (1 << 10),
			Entries: uint64(math.Floor(10*0.75) + 10),
		},
	}
	resp, err = rc.Do(ctx, req)
	require.NoError(t, err)
	require.Equal(t, 1, calls)
	require.Equal(t, expectedStats, resp)
}