feat(notes): banner when viewing an older shared version

Cache the note path on each snapshot so an old shared sha can find its
current version, and show a calm "older shared version — View latest"
banner. The exact snapshot is shown as-is; the banner only offers a jump
to the latest, never swapping content.

src/components/StackedNote.vue

@@ -68,12 +68,17 @@ const advanceStackTo = (newSha: string | null) => {
 
 const {
   path,
+  newerSha,
   content,
   rawContent,
   getRawContent,
   saveCacheNote,
   getEditedSha
 } = useFile(sha)
+
+// When this is an older snapshot of a still-existing note, jump the stack to
+// its current version (the exact snapshot is never swapped underneath you).
+const viewLatest = () => advanceStackTo(newerSha.value)
 const initialRawContent = ref<string | null>(null)
 const isMarkdown = computed(() =>
   path.value ? isMarkdownPath(path.value) : true
@@ -438,6 +443,16 @@ const onBadgeClick = async () => {
         <edit-note :key="editKey" v-model="rawContent" />
       </div>
       <template v-else-if="mode === 'read'">
+        <div v-if="newerSha" class="snapshot-banner">
+          <span>You're viewing an older shared version.</span>
+          <button
+            type="button"
+            class="snapshot-banner-action"
+            @click="viewLatest"
+          >
+            View latest
+          </button>
+        </div>
         <div
           v-if="displayedContent"
           class="note-content"
@@ -519,6 +534,28 @@ $border-color: rgba(18, 19, 58, 0.2);
   display: none;
 }
 
+.snapshot-banner {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 0.75rem;
+  margin: 0 0 1rem;
+  padding: 0.4rem 0.75rem;
+  border: 1px solid $border-color;
+  border-radius: 0.375rem;
+  font-size: 0.85em;
+}
+
+.snapshot-banner-action {
+  flex-shrink: 0;
+  padding: 0;
+  border: 0;
+  background: transparent;
+  color: var(--color-primary);
+  cursor: pointer;
+  text-decoration: underline;
+}
+
 .action {
   margin: 0;
 

src/hooks/useFile.hook.ts

@@ -2,6 +2,7 @@ import { computed, Ref, ref, toValue } from "vue"
 
 import { markdownBuilder } from "@/hooks/useMarkdown.hook"
 import { prepareNoteCache } from "@/modules/note/cache/prepareNoteCache"
+import { latestShaIfOlder } from "@/modules/note/snapshotStatus"
 import { queryFileContent } from "@/modules/repo/services/repo"
 import { useUserRepoStore } from "@/modules/repo/store/userRepo.store"
 
@@ -14,6 +15,16 @@ export const useFile = (sha: Ref<string> | string, retrieveContent = true) => {
     return file?.path
   })
 
+  // Path recovered from the cached note doc — lets us locate the latest version
+  // even when this (old) sha is no longer in store.files.
+  const cachedNotePath = ref<string | undefined>()
+
+  // When viewing an older snapshot of a known note, the note's current sha
+  // (null when already viewing the latest).
+  const newerSha = computed(() =>
+    latestShaIfOlder(shaValue, path.value ?? cachedNotePath.value, store.files)
+  )
+
   const {
     render,
     renderFromUTF8,
@@ -47,6 +58,8 @@ export const useFile = (sha: Ref<string> | string, retrieveContent = true) => {
     fromCache.value = !!cachedNote
 
     if (cachedNote) {
+      cachedNotePath.value = cachedNote.path ?? cachedNotePath.value
+
       if (from === "path") {
         queryFileContent(store.user, store.repo, shaValue).then(
           (fileContent) => {
@@ -104,6 +117,7 @@ export const useFile = (sha: Ref<string> | string, retrieveContent = true) => {
 
   return {
     path,
+    newerSha,
     content,
     rawContent,
     getRawContent,

src/modules/note/cache/prepareNoteCache.ts

@@ -21,7 +21,8 @@ export const buildNoteDocs = (
     _id: generateId(DataType.Note, sha),
     $type: DataType.Note,
     content,
-    editedSha
+    editedSha,
+    path
   }
   return path
     ? [base, { ...base, _id: generateId(DataType.Note, path) }]
@@ -71,7 +72,8 @@ export const prepareNoteCache = (sha: string, path?: string) => {
       _id: contentId,
       $type: DataType.Note,
       content,
-      editedSha: params?.editedSha
+      editedSha: params?.editedSha,
+      path: params?.path ?? path
     }
 
     if (params && params.path) {

src/modules/note/models/Note.ts

@@ -4,6 +4,9 @@ import { Model } from "@/data/models/Model"
 export interface Note extends Model<DataType.Note> {
   content: string
   editedSha?: string
+  // The note's path, stored so a cached snapshot can find its latest version
+  // even when its (old) sha is no longer in the repo file list.
+  path?: string
 }
 
 export interface PublicNoteListItem {

src/modules/note/snapshotStatus.spec.ts

@@ -0,0 +1,23 @@
+import { describe, expect, it } from "vitest"
+
+import { latestShaIfOlder } from "./snapshotStatus"
+
+const files = [
+  { path: "notes/a.md", sha: "current" },
+  { path: "notes/b.md", sha: "other" }
+]
+
+describe("latestShaIfOlder", () => {
+  it("returns the current sha when viewing an older version of a known note", () => {
+    expect(latestShaIfOlder("old", "notes/a.md", files)).toBe("current")
+  })
+
+  it("returns null when viewing the current version", () => {
+    expect(latestShaIfOlder("current", "notes/a.md", files)).toBeNull()
+  })
+
+  it("returns null when the path is unknown", () => {
+    expect(latestShaIfOlder("old", undefined, files)).toBeNull()
+    expect(latestShaIfOlder("old", "notes/missing.md", files)).toBeNull()
+  })
+})

src/modules/note/snapshotStatus.ts

@@ -0,0 +1,25 @@
+/**
+ * Return the note's current (latest) sha when `viewedSha` is NOT it — i.e. you
+ * are viewing an older version — otherwise null. "Older" is not inferred from
+ * the sha (a content hash has no order); it means "not the current sha for this
+ * path" per the repo file list.
+ *
+ * The caller must supply `notePath`. For a current sha it comes from the file
+ * list; for an older sha it comes from the cached snapshot's stored `path`
+ * (notes viewed while current carry it). When the path can't be resolved
+ * (foreign / evicted / pre-upgrade snapshot) this returns null and no banner is
+ * shown — graceful, never a false claim. Content is never swapped.
+ */
+export const latestShaIfOlder = (
+  viewedSha: string,
+  notePath: string | undefined,
+  files: ReadonlyArray<{ path?: string; sha?: string }>
+): string | null => {
+  if (!notePath) {
+    return null
+  }
+
+  const currentSha = files.find((file) => file.path === notePath)?.sha
+
+  return currentSha && currentSha !== viewedSha ? currentSha : null
+}