fix: scope page insights to reporting periods

internal/analytics/periods.go

@@ -244,6 +244,38 @@ func previousPersianSeason(year, startMonth int) (int, int) {
 	return year, startMonth
 }
 
+// PrecedingPeriodLabel returns the exact Persian label for the complete period
+// immediately before start. The label follows the same vocabulary as Periods.
+func PrecedingPeriodLabel(periodType string, start time.Time) (string, bool) {
+	location, err := time.LoadLocation("Asia/Tehran")
+	if err != nil {
+		return "", false
+	}
+	localStart := start.In(location)
+	switch periodType {
+	case "DAY":
+		day := localStart.AddDate(0, 0, -1)
+		year, month, dayOfMonth := gregorianToJalali(day.Year(), int(day.Month()), day.Day())
+		return fmt.Sprintf("روز %s %s %s", persianNumber(dayOfMonth), jalaliMonthNames[month-1], persianNumber(year)), true
+	case "WEEK":
+		weekStart := localStart.AddDate(0, 0, -7)
+		weekLastDay := localStart.AddDate(0, 0, -1)
+		_, startMonth, startDay := gregorianToJalali(weekStart.Year(), int(weekStart.Month()), weekStart.Day())
+		endYear, endMonth, endDay := gregorianToJalali(weekLastDay.Year(), int(weekLastDay.Month()), weekLastDay.Day())
+		return fmt.Sprintf("هفته %s %s تا %s %s %s", persianNumber(startDay), jalaliMonthNames[startMonth-1], persianNumber(endDay), jalaliMonthNames[endMonth-1], persianNumber(endYear)), true
+	case "JALALI_MONTH":
+		year, month, _ := gregorianToJalali(localStart.Year(), int(localStart.Month()), localStart.Day())
+		year, month = previousJalaliMonth(year, month)
+		return fmt.Sprintf("%s %s", jalaliMonthNames[month-1], persianNumber(year)), true
+	case "PERSIAN_SEASON":
+		year, month, _ := gregorianToJalali(localStart.Year(), int(localStart.Month()), localStart.Day())
+		year, month = previousPersianSeason(year, ((month-1)/3*3)+1)
+		return fmt.Sprintf("%s %s", persianSeasonNames[(month-1)/3], persianNumber(year)), true
+	default:
+		return "", false
+	}
+}
+
 func newPeriod(id, kind string, localStart, localEnd time.Time, label string, isDefault bool) Period {
 	return Period{
 		PeriodID: id, PeriodType: kind, StartAt: localStart.UTC(), EndAt: localEnd.UTC(),

internal/analytics/periods_test.go

@@ -94,3 +94,29 @@ func TestCompletePeriods(t *testing.T) {
 		t.Fatalf("completePeriods() returned %d defaults, want 1", defaultCount)
 	}
 }
+
+func TestPrecedingPeriodLabelUsesExactJalaliPeriod(t *testing.T) {
+	location, err := time.LoadLocation("Asia/Tehran")
+	if err != nil {
+		t.Fatal(err)
+	}
+	tests := []struct {
+		name       string
+		periodType string
+		start      time.Time
+		want       string
+	}{
+		{name: "day", periodType: "DAY", start: time.Date(2026, 7, 23, 0, 0, 0, 0, location), want: "روز ۳۱ تیر ۱۴۰۵"},
+		{name: "week", periodType: "WEEK", start: time.Date(2026, 8, 15, 0, 0, 0, 0, location), want: "هفته ۱۷ مرداد تا ۲۳ مرداد ۱۴۰۵"},
+		{name: "month", periodType: "JALALI_MONTH", start: time.Date(2026, 7, 23, 0, 0, 0, 0, location), want: "تیر ۱۴۰۵"},
+		{name: "season", periodType: "PERSIAN_SEASON", start: time.Date(2026, 6, 22, 0, 0, 0, 0, location), want: "بهار ۱۴۰۵"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, ok := PrecedingPeriodLabel(tt.periodType, tt.start)
+			if !ok || got != tt.want {
+				t.Fatalf("PrecedingPeriodLabel() = %q, %v; want %q, true", got, ok, tt.want)
+			}
+		})
+	}
+}