api: add statistics endpoint

api/comment_statistics.go

@@ -0,0 +1,36 @@
+package main
+
+import()
+
+func commentStatistics(domain string) ([]int64, error) {
+	statement := `
+		SELECT COUNT(comments.creationDate)
+		FROM (
+			SELECT to_char(date_trunc('day', (current_date - offs)), 'YYYY-MM-DD') AS date
+			FROM generate_series(0, 30, 1) AS offs
+		) gen LEFT OUTER JOIN comments
+		ON gen.date = to_char(date_trunc('day', comments.creationDate), 'YYYY-MM-DD') AND
+		   comments.domain=$1
+		GROUP BY gen.date
+		ORDER BY gen.date;
+	`
+	rows, err := db.Query(statement, domain)
+	if err != nil {
+		logger.Errorf("cannot get daily views: %v", err)
+		return []int64{}, errorInternal
+	}
+
+	defer rows.Close()
+
+	last30Days := []int64{}
+	for rows.Next() {
+		var count int64
+		if err = rows.Scan(&count); err != nil {
+			logger.Errorf("cannot get daily comments for the last month: %v", err)
+			return make([]int64, 0), errorInternal
+		}
+		last30Days = append(last30Days, count)
+	}
+
+	return last30Days, nil
+}