add `time` package

2 files changed, 112 insertions, 0 deletions

diff --git a/time/time.go b/time/time.go
new file mode 100644
index 0000000..97bd3d5
--- /dev/null
+++ b/time/time.go
@@ -0,0 +1,44 @@
+// Copyright © 2022 siddharth ravikumar <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+// ISO 8601 utility functions
+package time
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+)
+
+// ISO 8601 Duration regex for matching duration in PT3H4M60S format.
+var durationRegex = regexp.MustCompile(`PT(([0-9]{0,2})?H)?(([0-9]{0,2})?M)?(([0-9]{0,2}?)S)?`)
+
+// Converts ISO 8601 duration[1] to seconds.
+//
+// Recognizes durations in this format: PT3H4M60S
+//
+// [1]: https://en.wikipedia.org/wiki/ISO_8601#Durations
+func durationToSeconds(duration string) (int, error) {
+	m := durationRegex.FindStringSubmatch(duration)
+	if m == nil || len(m) == 0 {
+		return 0, fmt.Errorf("duration invalid: %v", duration)
+	}
+	hours, err := strconv.Atoi(m[2])
+	if err != nil {
+		hours = 0
+	}
+	mins, err := strconv.Atoi(m[4])
+	if err != nil {
+		mins = 0
+	}
+	secs, err := strconv.Atoi(m[6])
+	if err != nil {
+		secs = 0
+	}
+
+	// Add 'em all together.
+	secs += hours * 3600
+	secs += mins * 60
+
+	return secs, nil
+}
diff --git a/time/time_test.go b/time/time_test.go
new file mode 100644
index 0000000..d55783e
--- /dev/null
+++ b/time/time_test.go
@@ -0,0 +1,68 @@
+// Copyright © 2022 siddharth ravikumar <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package time
+
+import "testing"
+
+func TestDurationToSeconds(t *testing.T) {
+	secs, err := durationToSeconds("PT3H4M60S")
+	if err != nil {
+		t.Errorf("failed: %v", err)
+		return
+	}
+	if secs != 11100 {
+		t.Errorf("duration in seconds incorrect: %v", secs)
+		return
+	}
+
+	secs, err = durationToSeconds("PT4M60S")
+	if err != nil {
+		t.Errorf("failed: %v", err)
+		return
+	}
+	if secs != 300 {
+		t.Errorf("duration in seconds incorrect: %v", secs)
+		return
+	}
+
+	secs, err = durationToSeconds("PT12H")
+	if err != nil {
+		t.Errorf("failed: %v", err)
+		return
+	}
+	if secs != 43200 {
+		t.Errorf("duration in seconds incorrect: %v", secs)
+		return
+	}
+
+	secs, err = durationToSeconds("PT1H")
+	if err != nil {
+		t.Errorf("failed: %v", err)
+		return
+	}
+	if secs != 3600 {
+		t.Errorf("duration in seconds incorrect: %v", secs)
+		return
+	}
+
+	secs, err = durationToSeconds("PT2H")
+	if err != nil {
+		t.Errorf("failed: %v", err)
+		return
+	}
+	if secs != 7200 {
+		t.Errorf("duration in seconds incorrect: %v", secs)
+		return
+	}
+
+	secs, err = durationToSeconds("PT45M")
+	if err != nil {
+		t.Errorf("failed: %v", err)
+		return
+	}
+	if secs != 2700 {
+		t.Errorf("duration in seconds incorrect: %v", secs)
+		return
+	}
+}