feat(enakgame): weekly leaderboard

GET /customer/enakgame/leaderboard ranks the customers of an organization by
the EnakCoin they won from games in one week, Monday to Sunday in
Asia/Jakarta. Only completed, unflagged sessions count, by the week they
started; entry cost is not subtracted. Equal totals rank by who reached
theirs first, so no two customers share a rank.

Optional date (any day of the week, this week by default), game_id and limit
(10, at most 100). The response holds the top ranks and, under me, the
customer asking wherever they rank. Other customers are shown by a masked
name: the first word whole, the others by their first letter; a word with a
digit keeps only its first character.

The EnakGame web game shows it: integration-enakgame.md §10 (checklist now
§11) and RFC §11. The DB test needs TEST_DATABASE_URL.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/processor/game_leaderboard.go

@@ -0,0 +1,98 @@
+package processor
+
+import (
+	"context"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+
+	"apskel-pos-be/internal/models"
+	"apskel-pos-be/internal/repository"
+)
+
+const (
+	// leaderboardLimit is how many ranks a leaderboard shows unless asked, and
+	// leaderboardMaxLimit the most it shows.
+	leaderboardLimit    = 10
+	leaderboardMaxLimit = 100
+)
+
+// Leaderboard ranks the customers of the customer's organization by the EnakCoin they
+// won from games in one week, Monday to Sunday in Asia/Jakarta: this week, or the one
+// holding q.Date. A session counts in the week it started. Refunded, expired and
+// flagged sessions count for nothing.
+func (p *GameSessionProcessor) Leaderboard(ctx context.Context, customerID uuid.UUID, q models.EnakGameLeaderboardQuery) (*models.EnakGameLeaderboard, error) {
+	day := walletDay(p.now())
+	if s := strings.TrimSpace(q.Date); s != "" {
+		d, err := time.ParseInLocation("2006-01-02", s, walletDisplayLocation)
+		if err != nil {
+			return nil, gameSessionRejected("date must be YYYY-MM-DD")
+		}
+		day = d
+	}
+	weekStart := leaderboardWeekStart(day)
+	filter := repository.LeaderboardFilter{
+		CustomerID: customerID, From: weekStart, To: weekStart.AddDate(0, 0, 7), Limit: q.Limit,
+	}
+	if filter.Limit < 1 || filter.Limit > leaderboardMaxLimit {
+		filter.Limit = leaderboardLimit
+	}
+	if s := strings.TrimSpace(q.GameID); s != "" {
+		id, err := uuid.Parse(s)
+		if err != nil {
+			return nil, gameSessionRejected("game_id must be a UUID")
+		}
+		filter.GameID = &id
+	}
+	customer, err := p.customers.GetCustomer(ctx, customerID)
+	if err != nil {
+		return nil, err
+	}
+	filter.OrganizationID = customer.OrganizationID
+	rows, err := p.sessions.Leaderboard(ctx, filter)
+	if err != nil {
+		return nil, err
+	}
+	board := &models.EnakGameLeaderboard{
+		WeekStart: weekStart.Format("2006-01-02"), WeekEnd: weekStart.AddDate(0, 0, 6).Format("2006-01-02"),
+		GameID: filter.GameID, Entries: []models.EnakGameLeaderboardEntry{},
+	}
+	for _, row := range rows {
+		entry := models.EnakGameLeaderboardEntry{
+			Rank: row.Rank, Name: maskCustomerName(row.Name), Coins: row.Coins, IsMe: row.CustomerID == customerID,
+		}
+		if row.Rank <= filter.Limit {
+			board.Entries = append(board.Entries, entry)
+		}
+		if entry.IsMe {
+			me := entry
+			board.Me = &me
+		}
+	}
+	return board, nil
+}
+
+// leaderboardWeekStart is the Monday, at midnight in Asia/Jakarta, of the week of day.
+func leaderboardWeekStart(day time.Time) time.Time {
+	day = walletDay(day)
+	return day.AddDate(0, 0, -((int(day.Weekday()) + 6) % 7))
+}
+
+// maskCustomerName keeps the first word of a name and the first letter of every other
+// word: "Budi Santoso" is shown as "Budi S******". A word with a digit, as when a phone
+// number was used for the name, keeps only its first character, the first word too.
+func maskCustomerName(name string) string {
+	words := strings.Fields(name)
+	if len(words) == 0 {
+		return "Pemain"
+	}
+	for i, w := range words {
+		if i == 0 && !strings.ContainsAny(w, "0123456789") {
+			continue
+		}
+		r := []rune(w)
+		words[i] = string(r[0]) + strings.Repeat("*", len(r)-1)
+	}
+	return strings.Join(words, " ")
+}