Add DiffTimestamps function

src/lib/locale/DiffTimestamps.js

@@ -0,0 +1,55 @@
+// This file is part of React-Invenio-Forms
+// Copyright (C) 2024 CERN.
+//
+// React-Invenio-Forms is free software; you can redistribute it and/or modify it
+// under the terms of the MIT License; see LICENSE file for more details.
+
+import { DateTime } from "luxon";
+
+/**
+ * Create duration string for two given timestamps
+ *
+ * @param firstTimestamp string ISO timestamp
+ * @param secondTimestamp string ISO timestamp
+ * @returns {string} string representation of duration, i.e. 3 days
+ */
+export const diffTimestamps = (firstTimestamp, secondTimestamp, language = "en") => {
+  const first = DateTime.fromISO(firstTimestamp);
+  const second = DateTime.fromISO(secondTimestamp);
+  const duration = first.diff(second).reconfigure({ locale: language });
+  // If we used a newer version of luxon we could just do this:
+  // return duration.toHuman();
+
+  // instead return the largest unit and value (ignore everything smaller)
+  const rescale = duration.shiftTo(
+    "years",
+    "months",
+    "weeks",
+    "days",
+    "hours",
+    "minutes",
+    "seconds",
+    "milliseconds"
+  ); // in new luxon this is just duration.rescale()
+  const units = [
+    "years",
+    "months",
+    "weeks",
+    "days",
+    "hours",
+    "minutes",
+    "seconds",
+    "milliseconds",
+  ];
+
+  for (const unit of units) {
+    if (rescale[unit] && rescale[unit] > 0) {
+      if (rescale[unit] == 1) {
+        return rescale[unit] + " " + unit.slice(0, -1); // remove s
+      } else {
+        return rescale[unit] + " " + unit;
+      }
+    }
+  }
+  return "-"; // in case all components are zero
+};

src/lib/locale/index.js

@@ -1 +1,2 @@
 export { toRelativeTime } from "./RelativeTime";
+export { diffTimestamps } from "./DiffTimestamps";