time: add `IsCurrent`

2 files changed, 62 insertions, 1 deletions

diff --git a/time/time.go b/time/time.go
index 37ecdbb..89847ab 100644
--- a/time/time.go
+++ b/time/time.go
@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"regexp"
 	"strconv"
+	"strings"
 	"time"
 )
 
@@ -46,4 +47,39 @@ func Duration(duration string) (time.Duration, error) {
 
 	return d, nil
 }
+
+// Checks if the given ISO 8601 time is within the current time
+// period.
+//
+// `t` must be in 2022-08-07T02:00:00+00:00/PT1H format
+//
+// Returns true if the time `t` is the current time period; false
+// otherwise.
+func IsCurrent(t string) (bool, error) {
+	parts := strings.Split(t, "/")
+	if len(parts) != 2 {
+		return false, fmt.Errorf("time invalid")
+	}
+
+	// Parse time `t` into time intervals t1 and t2.
+	t1, err := time.Parse(time.RFC3339, parts[0])
+	if err != nil {
+		return false, fmt.Errorf("time invalid: %s", err)
+	}
+	d, err := Duration(parts[1])
+	if err != nil {
+		return false, fmt.Errorf("time invalid: %s", err)
+	}
+	t2 := t1.Add(d)
+
+	// Time `t` is in the current time period if current time is
+	// within the interval t1 and t2.
+	now := time.Now()
+	if t1.Before(now) && now.Before(t2) {
+		return true, nil
+	}
+	if t1.Equal(now) || t2.Equal(now) {
+		return true, nil
+	}
+	return false, nil
 }
diff --git a/time/time_test.go b/time/time_test.go
index 5bb6cb2..efb3078 100644
--- a/time/time_test.go
+++ b/time/time_test.go
@@ -3,7 +3,11 @@
 
 package time
 
-import "testing"
+import (
+	"fmt"
+	"testing"
+	"time"
+)
 
 func TestDurationToSeconds(t *testing.T) {
 	d, err := Duration("PT3H4M60S")
@@ -66,3 +70,24 @@ func TestDurationToSeconds(t *testing.T) {
 		return
 	}
 }
+
+func TestIsCurrent(t *testing.T) {
+	yes, err := IsCurrent("2022-08-07T01:00:00+00:00/PT1H")
+	if yes || err != nil {
+		t.Errorf("iscurrent failed: %v: %v", yes, err)
+		return
+	}
+
+	h, err := time.ParseDuration("-3600s")
+	if err != nil {
+		t.Errorf("-3600s parsing duration: %v", err)
+		return
+	}
+	ts := time.Now().Add(h).UTC().Format(time.RFC3339)
+	yes, err = IsCurrent(fmt.Sprintf("%s+00:00/PT2H", ts[:len(ts)-1]))
+	if !yes || err != nil {
+		t.Errorf("iscurrent failed: %v: %v", yes, err)
+		return
+	}
+
+}