1 files changed, 92 insertions, 0 deletions
diff --git a/app/assets/javascripts/work_items/notes/collapse_utils.js b/app/assets/javascripts/work_items/notes/collapse_utils.js
new file mode 100644
index 00000000000..db7b4530e2a
--- /dev/null
+++ b/app/assets/javascripts/work_items/notes/collapse_utils.js
@@ -0,0 +1,92 @@
+import { DESCRIPTION_TYPE, TIME_DIFFERENCE_VALUE } from '~/notes/constants';
+
+/**
+ * Checks the time difference between two notes from their 'created_at' dates
+ * returns an integer
+ */
+export const getTimeDifferenceInMinutes = (noteBeginning, noteEnd) => {
+  const descriptionNoteBegin = new Date(noteBeginning.createdAt);
+  const descriptionNoteEnd = new Date(noteEnd.createdAt);
+  const timeDifferenceMinutes = (descriptionNoteEnd - descriptionNoteBegin) / 1000 / 60;
+
+  return Math.ceil(timeDifferenceMinutes);
+};
+
+/**
+ * Checks if a note is a system note and if the content is description
+ *
+ * @param {Object} note
+ * @returns {Boolean}
+ */
+export const isDescriptionSystemNote = (note) => {
+  return note.system && note.body === DESCRIPTION_TYPE;
+};
+
+/**
+ * Collapses the system notes of a description type, e.g. Changed the description, n minutes ago
+ * the notes will collapse as long as they happen no more than 10 minutes away from each away
+ * in between the notes can be anything, another type of system note
+ * (such as 'changed the weight') or a comment.
+ *
+ * @param {Array} notes
+ * @returns {Array}
+ */
+export const collapseSystemNotes = (notes) => {
+  let lastDescriptionSystemNote = null;
+  let lastDescriptionSystemNoteIndex = -1;
+
+  return notes.reduce((acc, currentNote) => {
+    const note = currentNote.notes.nodes[0];
+    let lastStartVersionId = '';
+
+    if (isDescriptionSystemNote(note)) {
+      // is it the first one?
+      if (!lastDescriptionSystemNote) {
+        lastDescriptionSystemNote = note;
+      } else {
+        const timeDifferenceMinutes = getTimeDifferenceInMinutes(lastDescriptionSystemNote, note);
+
+        // are they less than 10 minutes apart from the same user?
+        if (
+          timeDifferenceMinutes > TIME_DIFFERENCE_VALUE ||
+          note.author.id !== lastDescriptionSystemNote.author.id ||
+          lastDescriptionSystemNote.systemNoteMetadata.descriptionVersion?.deleted
+        ) {
+          // update the previous system note
+          lastDescriptionSystemNote = note;
+        } else {
+          // set the first version to fetch grouped system note versions
+
+          lastStartVersionId = lastDescriptionSystemNote.systemNoteMetadata.descriptionVersion.id;
+
+          // delete the previous one
+          acc.splice(lastDescriptionSystemNoteIndex, 1);
+        }
+      }
+
+      // update the previous system note index
+      lastDescriptionSystemNoteIndex = acc.length;
+
+      acc.push({
+        notes: {
+          nodes: [
+            {
+              ...note,
+              systemNoteMetadata: {
+                ...note.systemNoteMetadata,
+                descriptionVersion: {
+                  ...note.systemNoteMetadata.descriptionVersion,
+                  startVersionId: lastStartVersionId,
+                },
+              },
+            },
+          ],
+        },
+      });
+    } else {
+      acc.push(currentNote);
+    }
+
+    return acc;
+  }, []);
+};