Add unit tests for dashboard repository and enhance BSON handling

internal/dashboard/repository.go

@@ -149,24 +149,20 @@ func (r *repository) Summary(ctx context.Context, closingWindowSec int64) (*Summ
 }
 
 func facetCount(facet bson.M, key string) int64 {
-	rows, ok := facet[key].(bson.A)
-	if !ok || len(rows) == 0 {
+	rows := facetRows(facet, key)
+	if len(rows) == 0 {
 		return 0
 	}
-	row, ok := rows[0].(bson.M)
-	if !ok {
-		return 0
-	}
-	return aggregateCount(row, "count")
+	return aggregateCount(asBSONMap(rows[0]), "count")
 }
 
 func facetCurrencyValue(facet bson.M) (string, float64) {
-	rows, ok := facet["currency_value"].(bson.A)
-	if !ok || len(rows) == 0 {
+	rows := facetRows(facet, "currency_value")
+	if len(rows) == 0 {
 		return defaultValueCurrency, 0
 	}
-	row, ok := rows[0].(bson.M)
-	if !ok {
+	row := asBSONMap(rows[0])
+	if row == nil {
 		return defaultValueCurrency, 0
 	}
 
@@ -177,6 +173,38 @@ func facetCurrencyValue(facet bson.M) (string, float64) {
 	return currency, toFloat64(row["total"])
 }
 
+func facetRows(facet bson.M, key string) []interface{} {
+	raw, ok := facet[key]
+	if !ok {
+		return nil
+	}
+	switch rows := raw.(type) {
+	case bson.A:
+		return []interface{}(rows)
+	case []interface{}:
+		return rows
+	default:
+		return nil
+	}
+}
+
+func asBSONMap(v interface{}) bson.M {
+	switch doc := v.(type) {
+	case bson.M:
+		return doc
+	case bson.D:
+		out := make(bson.M, len(doc))
+		for _, elem := range doc {
+			out[elem.Key] = elem.Value
+		}
+		return out
+	case map[string]interface{}:
+		return doc
+	default:
+		return nil
+	}
+}
+
 func (r *repository) Trend(ctx context.Context, days int, metric string, startUnix int64) (map[string]int64, error) {
 	field := trendTimestampField(metric)