(ui): Add custom duration field

ui/src/utils.ts

@@ -123,3 +123,24 @@ export function prettifyPayload(p: string) {
 export function currentUnixtime(): number {
   return Math.floor(Date.now() / 1000);
 }
+
+const durationRegex = /[1-9]([0-9]*)[s|m|h]/;
+// Parses the given string and returns the number of seconds if the input is valid.
+// Otherwise, it throws an error
+// Supported time units are "s", "m", "h"
+export function parseDuration(s: string): number {
+  if (!durationRegex.test(s)) {
+    throw new Error("invalid duration");
+  }
+  const val = parseInt(s.slice(0, -1));
+  switch (s.slice(-1)) {
+    case "s":
+      return val;
+    case "m":
+      return val * 60;
+    case "h":
+      return val * 6 * 60;
+    default:
+      throw new Error("invalid duration unit");
+  }
+}