Allow 'd' as day unit for -range flag. Closes #7.

flags/duration.go

@@ -0,0 +1,37 @@
+package flags
+
+import (
+	"flag"
+	"regexp"
+	"strconv"
+	"time"
+)
+
+type durationValue time.Duration
+
+var matchDay = regexp.MustCompile("[-+]?[0-9]*(\\.[0-9]*)?d")
+
+func (d *durationValue) Set(s string) error {
+	if is := matchDay.FindStringIndex(s); is != nil {
+		days, err := strconv.ParseFloat(s[is[0]:is[1]-1], 64)
+		if err != nil {
+			return err
+		}
+		s = s[:is[0]] + s[is[1]:] + strconv.FormatFloat(days*24, 'f', 6, 64) + "h"
+	}
+	v, err := time.ParseDuration(s)
+	*d = durationValue(v)
+	return err
+}
+
+func (d *durationValue) String() string {
+	return (*time.Duration)(d).String()
+}
+
+// Duration defines a flag for time.Duration values.
+// It works the same way as flag.Duration except that it als parses "XXd" values as days.
+func Duration(name string, value time.Duration, usage string) *time.Duration {
+	t := &value
+	flag.Var((*durationValue)(t), name, usage)
+	return t
+}

flags/duration_test.go

@@ -0,0 +1,49 @@
+package flags
+
+import (
+	"testing"
+	"time"
+)
+
+func TestDuration(t *testing.T) {
+	tests := []struct {
+		text    string
+		parsed  time.Duration
+		invalid bool
+	}{
+		{text: "1h30.5m3s", parsed: time.Hour + 30*time.Minute + 33*time.Second},
+		{text: "1h", parsed: time.Hour},
+		{text: "1h2h", parsed: 3 * time.Hour},
+		{text: "30m1h", parsed: time.Hour + 30*time.Minute},
+		{text: "1d", parsed: 24 * time.Hour},
+		{text: "0.50d", parsed: 12 * time.Hour},
+		{text: ".5d", parsed: 12 * time.Hour},
+		{text: "1d1h", parsed: 25 * time.Hour},
+		{text: "1h1d", parsed: 25 * time.Hour},
+		{text: "1h1d60m", parsed: 26 * time.Hour},
+		{text: "", invalid: true},
+		{text: "bla", invalid: true},
+	}
+
+	for i, tt := range tests {
+		var u durationValue
+		if err := u.Set(tt.text); err != nil {
+			if !tt.invalid {
+				t.Errorf("parsing '%s' failed unexpectedly: %v", tt.text, err)
+			}
+			continue
+		}
+		if tt.invalid {
+			t.Errorf("parsing '%s' should have failed", tt.text)
+			continue
+		}
+		if time.Duration(u) != tt.parsed {
+			t.Errorf(`
+%d.
+Input:    %s
+Expected: %v
+Got       %v`, i, tt.text, tt.parsed, u)
+		}
+	}
+
+}

main.go

@@ -43,7 +43,7 @@ func main() {
 		promServer  = flag.String("url", "", "Required. URL of Prometheus server.")
 		query       = flag.String("query", "", "Required. PQL query.")
 		queryTime   = flags.UnixTime("time", time.Now(), "Required. Time for query (default is now). Format like the default format of the Unix date command.")
-		duration    = flag.Duration("range", 0, "Required. Time to look back to. Format: 12h34m56s.")
+		duration    = flags.Duration("range", 0, "Required. Time to look back to. Format: 5d12h34m56s")
 		title       = flag.String("title", "Prometheus metrics", "Optional. Title of graph.")
 		//
 		format = flag.String("format", "png", "Optional. Image format. For possible values see: https://godoc.org/github.com/gonum/plot/vg/draw#NewFormattedCanvas")