Support day format in human-friendly time formats

So one does not have to calculate days as multiples of 24 hours in head
when older logs are needed.

README.md

@@ -24,7 +24,7 @@ Author - [Luca Grulla](https://www.lucagrulla.com)  - [https://www.lucagrulla.co
 * **Flexible date and time parser**.
   * You can work with either `Local` timezone or `UTC` (default).
   * Flexible parsing.
-    * Human friendly formats, i.e. `1h20m`  to indicate 1 hour and 20 minutes ago.
+    * Human friendly formats, i.e. `2d1h20m` to indicate 2 days, 1 hour and 20 minutes ago.
     * a specific hour, i.e. `13:10` to indicate 13:10 of today.
     * a full timestamp `2018-10-20T8:53`.
 * **multi log groups tailing** tail multiple log groups  in parallel: `cw tail tail my-auth-service my-web`
@@ -114,12 +114,12 @@ go get github.com/lucagrulla/cw
         -s, --stream-name      Print the log stream name this event belongs to.
         -n, --group-name       Print the log log group name this event belongs to.
         -b, --start="2018-12-25T09:34:45"
-                                The UTC start time. Passed as either date/time or human-friendly format. The human-friendly format accepts the number of hours and minutes prior to the present. Denote hours with
-                                'h' and minutes with 'm' i.e. 80m, 4h30m. If just time is used (format: hh[:mm]) it is expanded to today at the given time. Full available date/time format:
-                                2017-02-27[T09[:00[:00]].
-        -e, --end=""           The UTC end time. Passed as either date/time or human-friendly format. The human-friendly format accepts the number of hours and minutes prior to the present. Denote hours with
-                                'h' and minutes with 'm' i.e. 80m, 4h30m.If just time is used (format: hh[:mm]) it is expanded to today at the given time. Full available date/time format:
-                                2017-02-27[T09[:00[:00]].
+                               The UTC start time. Passed as either date/time or human-friendly format. The human-friendly format accepts the number of days, hours and minutes prior to the present. Denote days with
+                               'd', hours with 'h' and minutes with 'm' i.e. 80m, 4h30m, 2d4h. If just time is used (format: hh[:mm]) it is expanded to today at the given time. Full available date/time format:
+                               2017-02-27[T09[:00[:00]].
+        -e, --end=""           The UTC end time. Passed as either date/time or human-friendly format. The human-friendly format accepts the number of days, hours and minutes prior to the present. Denote days with
+                               'd', hours with 'h' and minutes with 'm' i.e. 80m, 4h30m, 2d4h. If just time is used (format: hh[:mm]) it is expanded to today at the given time. Full available date/time format:
+                               2017-02-27[T09[:00[:00]].
         -l, --local            Treat date and time in Local timezone.
         -g, --grep=""          Pattern to filter logs by. See http://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/FilterAndPatternSyntax.html for syntax.
         -v, --grepv=""         Equivalent of grep --invert-match. Invert match pattern to filter logs by.
@@ -141,6 +141,7 @@ go get github.com/lucagrulla/cw
   * `cw tail -f my-log-group:my-log-stream-prefix`
   * `cw tail -f my-log-group:my-log-stream-prefix my-log-group2`
   * `cw tail -f my-log-group:my-log-stream-prefix -b2017-01-01T08:10:10 -e2017-01-01T08:05:00`  
+  * `cw tail -f my-log-group:my-log-stream-prefix -b7d` to start from 7 days ago.
   * `cw tail -f my-log-group:my-log-stream-prefix -b3h` to start from 3 hours ago.
   * `cw tail -f my-log-group:my-log-stream-prefix -b100m`  to start from 100 minutes ago.
   * `cw tail -f my-log-group:my-log-stream-prefix -b2h30m`  to start from 2 hours and 30 minutes ago.

main.go

@@ -50,14 +50,14 @@ var (
 	printStreamName = tailCommand.Flag("stream-name", "Print the log stream name this event belongs to.").Short('s').Default("false").Bool()
 	printGroupName  = tailCommand.Flag("group-name", "Print the log group name this event belongs to.").Short('n').Default("false").Bool()
 	startTime       = tailCommand.Flag("start", "The UTC start time. Passed as either date/time or human-friendly format."+
-		" The human-friendly format accepts the number of hours and minutes prior to the present. "+
-		"Denote hours with 'h' and minutes with 'm' i.e. 80m, 4h30m."+
+		" The human-friendly format accepts the number of days, hours and minutes prior to the present. "+
+		"Denote days with 'd', hours with 'h' and minutes with 'm' i.e. 80m, 4h30m, 2d4h."+
 		" If just time is used (format: hh[:mm]) it is expanded to today at the given time."+
 		" Full available date/time format: 2017-02-27[T09[:00[:00]].").
 		Short('b').Default(time.Now().UTC().Add(-30 * time.Second).Format(timeFormat)).String()
 	endTime = tailCommand.Flag("end", "The UTC end time. Passed as either date/time or human-friendly format. "+
-		"The human-friendly format accepts the number of hours and minutes prior to the present. "+
-		"Denote hours with 'h' and minutes with 'm' i.e. 80m, 4h30m."+
+		" The human-friendly format accepts the number of days, hours and minutes prior to the present. "+
+		"Denote days with 'd', hours with 'h' and minutes with 'm' i.e. 80m, 4h30m, 2d4h."+
 		"If just time is used (format: hh[:mm]) it is expanded to today at the given time. Full available date/time format: 2017-02-27[T09[:00[:00]].").
 		Short('e').Default("").String()
 	local = tailCommand.Flag("local", "Treat date and time in Local timezone.").Short('l').Default("false").Bool()
@@ -93,10 +93,14 @@ func timestampToTime(timeStamp *string) (time.Time, error) {
 		mm, _ := strconv.Atoi(res[2])
 
 		return time.Date(y, m, d, t, mm, 0, 0, zone), nil
-	} else if regexp.MustCompile(`^\d{1,}h$|^\d{1,}m$|^\d{1,}h\d{1,}m$`).MatchString(*timeStamp) {
-		d, _ := time.ParseDuration(*timeStamp)
-
-		t := time.Now().In(zone).Add(-d)
+	} else if res := regexp.MustCompile(
+		`^(?:(?P<Day>\d{1,})(?:d))?(?P<HourMinute>(?:\d{1,}h)?(?:\d{1,}m)?)?$`).FindStringSubmatch(
+		*timeStamp); res != nil {
+		// Unfortunately, ParseDuration does not support day time unit
+		days, _ := strconv.Atoi(res[1])
+		d, _ := time.ParseDuration(res[2])
+
+		t := time.Now().In(zone).AddDate(0, 0, -days).Add(-d)
 		y, m, dd := t.Date()
 		return time.Date(y, m, dd, t.Hour(), t.Minute(), 0, 0, zone), nil
 	}

main_test.go

@@ -54,13 +54,32 @@ func TestTimestampToTime(t *testing.T) {
 func TestHumanReadableTimeToTime(t *testing.T) {
 	assert := assert.New(t)
 
-	s := "32h"
-	dd, _ := time.ParseDuration(s)
-	x := time.Now().UTC().Add(-dd)
+	s := "2d"
+	x := time.Now().UTC().AddDate(0, 0, -2)
 
 	y, m, d := x.Date()
 
 	parsedTime, _ := timestampToTime(&s)
+	assert.Equal(time.Date(y, m, d, x.Hour(), x.Minute(), 0, 0, time.UTC),
+		parsedTime, "wrong parsing for input %s", s)
+
+	s = "03d50m"
+	dd, _ := time.ParseDuration(`50m`)
+	x = time.Now().UTC().AddDate(0, 0, -3).Add(-dd)
+
+	y, m, d = x.Date()
+
+	parsedTime, _ = timestampToTime(&s)
+	assert.Equal(time.Date(y, m, d, x.Hour(), x.Minute(), 0, 0, time.UTC),
+		parsedTime, "wrong parsing for input %s", s)
+
+	s = "32h"
+	dd, _ = time.ParseDuration(s)
+	x = time.Now().UTC().Add(-dd)
+
+	y, m, d = x.Date()
+
+	parsedTime, _ = timestampToTime(&s)
 	assert.Equal(time.Date(y, m, d, x.Hour(), x.Minute(), 0, 0, time.UTC), parsedTime, "wrong parsing for input %s", s)
 
 	s = "50m"