Phase 8: version history + export (trust foundation)

Version history: new document_versions table (migration 0003) holding
full-body snapshots that cascade with the doc. Throttled auto-snapshots
on save (>=3min apart, max 40/doc, pruned), explicit manual restore
points, and a pre_restore safety copy taken before each restore so
restoring is itself undoable. Endpoints under /api/docs/:id/versions,
all owner-scoped. Empties and bare renames never snapshot.

Export: pure-Go Tiptap-JSON -> Markdown / HTML / plain-text / docx
(no cgo/pandoc, single-binary intact), CJK-safe with RFC 5987
filenames. docx is a hand-built OOXML zip. PDF is handled client-side
via the browser print dialog + an @media print stylesheet so CJK
renders with the reader's own fonts.

Frontend: ExportMenu (downloads + Print/PDF) and HistoryPanel
(snapshot list, preview, restore) wired into the title row; bilingual
zh-first to match chrome. Restore remounts the editor via editorEpoch.

Stop saving empty docs: blank Untitled drafts now reuse-on-create and
self-discard when navigated away from (refs avoid stale closures).

Tests: versions_test.go, export_test.go (incl. valid-zip docx).
go build/vet/test, tsc, vite build all clean; live end-to-end smoke
verified snapshot/throttle/restore/export.

Claude-Session: https://claude.ai/code/session_016Yr6jELuRc7hyzYLccQKZd

web/src/App.tsx

@@ -6,6 +6,8 @@ import { useSpellChecker } from './hooks/useSpellChecker'
 import { DocList } from './components/DocList/DocList'
 import { EditorCore, type EditorChange } from './components/Editor/EditorCore'
 import { ToneSelect } from './components/Editor/ToneSelect'
+import { ExportMenu } from './components/Export/ExportMenu'
+import { HistoryPanel } from './components/History/HistoryPanel'
 import { StatusBar } from './components/StatusBar/StatusBar'
 import { PetalCompanion } from './components/Companion/PetalCompanion'
 import { UpdateBanner } from './components/UpdateBanner/UpdateBanner'
@@ -29,6 +31,28 @@ export default function App() {
   // Monotonic counters the companion watches to react to writing + accepts.
   const [editTick, setEditTick] = useState(0)
   const [acceptTick, setAcceptTick] = useState(0)
+  // History drawer visibility, and an epoch bumped on restore to force the
+  // editor to remount with the restored content (its initialContent is read
+  // only on mount).
+  const [historyOpen, setHistoryOpen] = useState(false)
+  const [editorEpoch, setEditorEpoch] = useState(0)
+
+  // Live mirrors of the current doc's editable fields so the "discard blank
+  // drafts on navigation" logic can read the latest values without rebuilding
+  // callbacks on every keystroke.
+  const currentDocRef = useRef(currentDoc)
+  const titleRef = useRef(title)
+  const wordCountRef = useRef(wordCount)
+  currentDocRef.current = currentDoc
+  titleRef.current = title
+  wordCountRef.current = wordCount
+
+  // A throwaway blank draft: no words and still the default/empty title. We
+  // delete these on navigation rather than leave orphan "Untitled" docs behind.
+  const isBlankDraft = useCallback(() => {
+    const t = titleRef.current.trim()
+    return wordCountRef.current === 0 && (t === '' || t === 'Untitled')
+  }, [])
 
   const { status, schedule, saveNow } = useAutoSave(currentDoc?.id ?? null)
   const {
@@ -49,6 +73,9 @@ export default function App() {
 
   const openDoc = useCallback(
     async (id: string) => {
+      // Decide the leaving doc's fate before any await mutates state.
+      const leaving = currentDocRef.current
+      const leavingBlank = isBlankDraft()
       await saveNow() // flush any pending edits to the doc we're leaving
       const doc = await api.getDoc(id)
       setCurrentDoc(doc)
@@ -56,8 +83,14 @@ export default function App() {
       setWordCount(doc.word_count)
       setTone(doc.tone || 'general')
       setDocText(doc.content_text)
+      // Leaving an untouched blank draft for a different doc? Drop it silently
+      // (best-effort cleanup — a 404 just means it's already gone).
+      if (leaving && leaving.id !== id && leavingBlank) {
+        api.deleteDoc(leaving.id).catch(() => {})
+        setDocs((prev) => prev.filter((d) => d.id !== leaving.id))
+      }
     },
-    [saveNow],
+    [saveNow, isBlankDraft],
   )
 
   // Initial load: fetch the list, opening the first doc (or creating one).
@@ -90,6 +123,9 @@ export default function App() {
   }, [openDoc])
 
   const handleCreate = useCallback(async () => {
+    // Already sitting on a fresh blank draft? Reuse it instead of stacking
+    // another empty "Untitled" on top.
+    if (currentDocRef.current && isBlankDraft()) return
     await saveNow()
     const fresh = await api.createDoc()
     setDocs((prev) => [
@@ -101,7 +137,7 @@ export default function App() {
     setWordCount(0)
     setTone(fresh.tone || 'general')
     setDocText('')
-  }, [saveNow])
+  }, [saveNow, isBlankDraft])
 
   const handleDelete = useCallback(
     async (id: string) => {
@@ -179,6 +215,21 @@ export default function App() {
     [removeSuggestion],
   )
 
+  // After restoring a version, swap the restored doc into the editor. Bumping
+  // editorEpoch remounts EditorCore so it picks up the restored content.
+  const handleRestored = useCallback(
+    (doc: Document) => {
+      setCurrentDoc(doc)
+      setTitle(doc.title)
+      setWordCount(doc.word_count)
+      setTone(doc.tone || 'general')
+      setDocText(doc.content_text)
+      patchSummary(doc.id, { title: doc.title, word_count: doc.word_count })
+      setEditorEpoch((n) => n + 1)
+    },
+    [patchSummary],
+  )
+
   // Escape always restores the sidebar while in distraction-free mode.
   useEffect(() => {
     if (!focusMode) return
@@ -211,7 +262,7 @@ export default function App() {
     <div className="flex h-full flex-col">
       <header
         onMouseDown={handleChromeDown}
-        className="flex h-12 shrink-0 items-center gap-2 px-5"
+        className="petal-no-print flex h-12 shrink-0 items-center gap-2 px-5"
         style={{ borderBottom: '1px solid var(--color-border)' }}
       >
         <span className="text-xl">🌸</span>
@@ -219,7 +270,9 @@ export default function App() {
       </header>
 
       <div className="flex min-h-0 flex-1">
-        <div className={`petal-sidebar shrink-0${focusMode ? ' petal-sidebar-hidden' : ''}`}>
+        <div
+          className={`petal-no-print petal-sidebar shrink-0${focusMode ? ' petal-sidebar-hidden' : ''}`}
+        >
           <DocList
             docs={docs}
             selectedId={currentDoc?.id ?? null}
@@ -246,10 +299,32 @@ export default function App() {
                       className="min-w-0 flex-1 bg-transparent text-3xl font-extrabold text-plum focus:outline-none"
                       style={{ fontFamily: 'var(--font-ui)' }}
                     />
-                    <ToneSelect value={tone} onChange={handleToneChange} />
+                    <div className="petal-no-print shrink-0">
+                      <ToneSelect value={tone} onChange={handleToneChange} />
+                    </div>
+                    <button
+                      type="button"
+                      onClick={() => setHistoryOpen(true)}
+                      aria-label="Version history"
+                      title="Browse and restore earlier versions"
+                      className="petal-no-print inline-flex h-9 shrink-0 items-center gap-1.5 whitespace-nowrap px-3 text-sm font-bold"
+                      style={{
+                        borderRadius: 'var(--radius-pill)',
+                        background: 'var(--color-surface)',
+                        color: 'var(--color-plum)',
+                        boxShadow: 'var(--shadow-soft)',
+                      }}
+                    >
+                      <span aria-hidden>🕘</span>
+                      <span>历史</span>
+                      <span style={{ color: 'var(--color-muted)' }}>· History</span>
+                    </button>
+                    <div className="petal-no-print">
+                      <ExportMenu docId={currentDoc.id} />
+                    </div>
                   </div>
                   <EditorCore
-                    key={currentDoc.id}
+                    key={`${currentDoc.id}:${editorEpoch}`}
                     docId={currentDoc.id}
                     initialContent={currentDoc.content}
                     onChange={handleEditorChange}
@@ -264,7 +339,7 @@ export default function App() {
                   />
                 </div>
               </div>
-              <div onMouseDown={handleChromeDown}>
+              <div className="petal-no-print" onMouseDown={handleChromeDown}>
                 <StatusBar
                   wordCount={wordCount}
                   text={docText}
@@ -285,14 +360,24 @@ export default function App() {
         </main>
       </div>
 
+      {historyOpen && currentDoc && (
+        <HistoryPanel
+          docId={currentDoc.id}
+          onClose={() => setHistoryOpen(false)}
+          onRestored={handleRestored}
+        />
+      )}
+
       {updateAvailable && <UpdateBanner />}
 
-      <PetalCompanion
-        wordCount={wordCount}
-        saveStatus={status}
-        editTick={editTick}
-        acceptTick={acceptTick}
-      />
+      <div className="petal-no-print">
+        <PetalCompanion
+          wordCount={wordCount}
+          saveStatus={status}
+          editTick={editTick}
+          acceptTick={acceptTick}
+        />
+      </div>
     </div>
   )
 }