Add total_count field in meta for leaderboard endpoint

internal/data/balances.go

@@ -39,6 +39,8 @@ type BalancesQ interface {
 	GetWithRank(nullifier string) (*Balance, error)
 	SelectWithRank() ([]Balance, error)
 
+	Count() (int64, error)
+
 	// WithoutPassportEvent returns balances which already
 	// have scanned passport, but there no claimed events
 	// for this. Filters are not applied.

internal/data/pg/balances.go

@@ -17,6 +17,7 @@ type balances struct {
 	selector squirrel.SelectBuilder
 	updater  squirrel.UpdateBuilder
 	rank     squirrel.SelectBuilder
+	counter  squirrel.SelectBuilder
 }
 
 func NewBalances(db *pgdb.DB) data.BalancesQ {
@@ -25,6 +26,7 @@ func NewBalances(db *pgdb.DB) data.BalancesQ {
 		selector: squirrel.Select("*").From(balancesTable),
 		updater:  squirrel.Update(balancesTable),
 		rank:     squirrel.Select("*, ROW_NUMBER() OVER (ORDER BY amount DESC, updated_at ASC) AS rank").From(balancesTable),
+		counter:  squirrel.Select("COUNT(*) as count").From(balancesTable),
 	}
 }
 
@@ -124,6 +126,18 @@ func (q *balances) Get() (*data.Balance, error) {
 	return &res, nil
 }
 
+func (q *balances) Count() (int64, error) {
+	res := struct {
+		Count int64 `db:"count"`
+	}{}
+
+	if err := q.db.Get(&res, q.counter); err != nil {
+		return 0, fmt.Errorf("get balance: %w", err)
+	}
+
+	return res.Count, nil
+}
+
 func (q *balances) GetWithRank(nullifier string) (*data.Balance, error) {
 	var res data.Balance
 	stmt := fmt.Sprintf(`
@@ -205,5 +219,6 @@ func (q *balances) applyCondition(cond squirrel.Sqlizer) data.BalancesQ {
 	q.selector = q.selector.Where(cond)
 	q.updater = q.updater.Where(cond)
 	q.rank = q.rank.Where(cond)
+	q.counter = q.counter.Where(cond)
 	return q
 }

internal/service/handlers/leaderboard.go

@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"encoding/json"
 	"net/http"
 
 	"github.com/rarimo/rarime-points-svc/internal/data"
@@ -24,16 +25,30 @@ func Leaderboard(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	resp := newLeaderboardResponse(leaders)
+	leadersCount, err := BalancesQ(r).FilterDisabled().Count()
+	if err != nil {
+		Log(r).WithError(err).Error("Failed to leaders count")
+		ape.RenderErr(w, problems.InternalError())
+		return
+	}
+
+	resp := newLeaderboardResponse(leaders, leadersCount)
 	resp.Links = req.GetLinks(r)
 	ape.Render(w, resp)
 }
 
-func newLeaderboardResponse(balances []data.Balance) resources.BalanceListResponse {
+func newLeaderboardResponse(balances []data.Balance, totalLeaders int64) resources.BalanceListResponse {
 	list := make([]resources.Balance, len(balances))
 	for i, balance := range balances {
 		list[i] = newBalanceModel(balance)
 	}
 
-	return resources.BalanceListResponse{Data: list}
+	// must never panic
+	serMeta, _ := json.Marshal(struct {
+		TotalCount int64 `json:"total_count"`
+	}{
+		TotalCount: totalLeaders,
+	})
+
+	return resources.BalanceListResponse{Data: list, Meta: serMeta}
 }