Read ds settings and use it for trends

pkg/gtime/gtime.go

@@ -0,0 +1,36 @@
+package gtime
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+	"time"
+)
+
+var dateUnitPattern = regexp.MustCompile(`^(\d+)([dwMy])$`)
+
+// ParseInterval parses an interval with support for all units that Grafana uses.
+func ParseInterval(interval string) (time.Duration, error) {
+	result := dateUnitPattern.FindSubmatch([]byte(interval))
+
+	if len(result) != 3 {
+		return time.ParseDuration(interval)
+	}
+
+	num, _ := strconv.Atoi(string(result[1]))
+	period := string(result[2])
+	now := time.Now()
+
+	switch period {
+	case "d":
+		return now.Sub(now.AddDate(0, 0, -num)), nil
+	case "w":
+		return now.Sub(now.AddDate(0, 0, -num*7)), nil
+	case "M":
+		return now.Sub(now.AddDate(0, -num, 0)), nil
+	case "y":
+		return now.Sub(now.AddDate(-num, 0, 0)), nil
+	}
+
+	return 0, fmt.Errorf("ParseInterval: invalid duration %q", interval)
+}