fix: chunk auto-backup writes + spinner on manual "Backup now"

Bridge.writeFile had the same URL-length trap saveFile did: a large
auto-backup base64'd into a single cmd://file/write URL blew past
WebView2's ~2MB navigation cap, so backups of big vaults failed
silently (or blanked the page) — for BOTH the manual "Backup now"
button and the silent scheduled run.

- writeFile now streams payloads over ~1MB in chunks (reusing the same
  file/chunk transport as saveFile), committed via a new
  file/write-commit. Delphi shares the decode+write logic through a new
  WriteDecodedFile helper and the existing FFileSaveChunks buffer.
- runAutoBackupNow(silent): the manual run shows the busy overlay
  ("Reading vault… N/total" → "Encrypting backup…" → "Writing file… N%")
  since a 20MB backup takes ~30s; the scheduled on-unlock run passes
  silent=true (no overlay, but still chunked so it no longer fails on
  large vaults).
- Fixed the "Backup now" click handler passing the click Event as the
  silent arg (truthy → would have suppressed the spinner and swallowed
  errors); wrapped in () => runAutoBackupNow().
- Pre-sync backup benefits from the chunked writeFile automatically.

Rebuild: BuildAssets + F9 (UMainForm.pas changed).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

delphi-backend/UMainForm.pas

@@ -115,6 +115,9 @@ type
     // (chunked): decode the base64, show the Save dialog, write, and fire
     // Bridge.onFileSaveResult back to JS.
     procedure SaveDecodedFile(const AName, AB64, AReqId: string);
+    // Silent write to a fixed path (auto-backup / sync pre-backup). Shared
+    // by cmd://file/write (single-shot) and file/write-commit (chunked).
+    procedure WriteDecodedFile(const APath, AB64, AReqId: string);
     procedure LogLine(const AMsg: string);
     procedure UpdateButtons;
     procedure NavigateToVault;
@@ -508,6 +511,40 @@ begin
     BoolToStr(LOk, True).ToLower + ',"' + LEscPath + '","' + LEscErr + '")');
 end;
 
+procedure TMainForm.WriteDecodedFile(const APath, AB64, AReqId: string);
+var
+  LOk: Boolean;
+  LErr: string;
+begin
+  LOk  := False;
+  LErr := '';
+  try
+    var LBytes := TNetEncoding.Base64.DecodeStringToBytes(AB64);
+    var LStream := TFileStream.Create(APath, fmCreate);
+    try
+      if Length(LBytes) > 0 then
+        LStream.WriteBuffer(LBytes[0], Length(LBytes));
+    finally
+      LStream.Free;
+    end;
+    LOk := True;
+    LogLine(Format('File written: %s (%d bytes)', [APath, Length(LBytes)]));
+  except
+    on E: Exception do
+    begin
+      LErr := E.Message;
+      LogLine('File write FAILED for "' + APath + '": ' + LErr);
+    end;
+  end;
+  var LEscReq := StringReplace(AReqId, '"', '\"', [rfReplaceAll]);
+  var LEscErr := StringReplace(LErr, '\', '\\', [rfReplaceAll]);
+  LEscErr := StringReplace(LEscErr, '"', '\"', [rfReplaceAll]);
+  WebBrowser.ExecuteJavaScript(
+    'if(window.Bridge&&Bridge.onFileWriteResult)' +
+    'Bridge.onFileWriteResult("' + LEscReq + '",' +
+    BoolToStr(LOk, True).ToLower + ',"' + LEscErr + '")');
+end;
+
 procedure TMainForm.NavigateToVault;
 begin
   FPendingURL := 'http://127.0.0.1:' + FServer.BoundPort.ToString + '/index.html';
@@ -1240,37 +1277,29 @@ begin
   // cmd://file/write?path=<full>&data=<base64>&reqId=<id>
   // Callback: Bridge.onFileWriteResult(reqId, ok, error)
   else if ACmd = 'file/write' then
+    // Single-shot silent write (small payload).
+    WriteDecodedFile(GetParam('path'), GetParam('data'), GetParam('reqId'))
+
+  // Chunked silent write: chunks accumulated via file/chunk, committed
+  // here (large auto-backups exceed a single cmd:// URL otherwise).
+  else if ACmd = 'file/write-commit' then
   begin
-    var LPath := GetParam('path');
-    var LData := GetParam('data');
     var LReqId := GetParam('reqId');
-    var LOk := False;
+    var LSB: TStringBuilder;
-    var LErr := '';
+    if FFileSaveChunks.TryGetValue(LReqId, LSB) then
-    try
+    begin
-      var LBytes := TNetEncoding.Base64.DecodeStringToBytes(LData);
+      var LFull := LSB.ToString;
-      var LStream := TFileStream.Create(LPath, fmCreate);
+      LSB.Free;
-      try
+      FFileSaveChunks.Remove(LReqId);
-        if Length(LBytes) > 0 then
+      WriteDecodedFile(GetParam('path'), LFull, LReqId);
-          LStream.WriteBuffer(LBytes[0], Length(LBytes));
+    end
-      finally
+    else
-        LStream.Free;
+    begin
-      end;
+      var LEscReq := StringReplace(LReqId, '"', '\"', [rfReplaceAll]);
-      LOk := True;
+      WebBrowser.ExecuteJavaScript(
-      LogLine(Format('File written: %s (%d bytes)', [LPath, Length(LBytes)]));
+        'if(window.Bridge&&Bridge.onFileWriteResult)' +
-    except
+        'Bridge.onFileWriteResult("' + LEscReq + '",false,"no chunks buffered")');
-      on E: Exception do
-      begin
-        LErr := E.Message;
-        LogLine('File write FAILED for "' + LPath + '": ' + LErr);
-      end;
     end;
-    var LEscReq := StringReplace(LReqId, '"', '\"', [rfReplaceAll]);
-    var LEscErr := StringReplace(LErr, '\', '\\', [rfReplaceAll]);
-    LEscErr := StringReplace(LEscErr, '"', '\"', [rfReplaceAll]);
-    WebBrowser.ExecuteJavaScript(
-      'if(window.Bridge&&Bridge.onFileWriteResult)' +
-      'Bridge.onFileWriteResult("' + LEscReq + '",' +
-      BoolToStr(LOk, True).ToLower + ',"' + LEscErr + '")');
   end
 
   // ---- Auto-backup: list files in dir matching name prefix --------------

js/app.js

@@ -306,25 +306,64 @@ const Bridge = (() => {
             if (r) { delete folderPickResolvers[reqId]; r(path || ''); }
         },
 
-        writeFile(path, content) {
+        writeFile(path, content, onProgress) {
             if (!active) return Promise.resolve({ ok: false, error: 'bridge offline' });
             let bytes;
             if (typeof content === 'string') bytes = new TextEncoder().encode(content);
             else bytes = content;
             const b64 = bytesToBase64(bytes);
             const reqId = 'fw_' + Date.now() + '_' + Math.random().toString(36).slice(2, 6);
-            return new Promise(resolve => {
+            // Same URL-length trap as saveFile: a big auto-backup base64'd
-                fileWriteResolvers[reqId] = resolve;
+            // into a single cmd:// URL blows past WebView2's cap and the
-                cmd('cmd://file/write?path=' + encodeURIComponent(path) +
+            // write fails (silently, or blanks the page). Chunk it.
-                    '&data=' + encodeURIComponent(b64) +
+            const CHUNK = 1000000;
-                    '&reqId=' + encodeURIComponent(reqId));
+            if (b64.length <= CHUNK) {
-                setTimeout(() => {
+                return new Promise(resolve => {
-                    if (fileWriteResolvers[reqId]) {
+                    fileWriteResolvers[reqId] = resolve;
-                        delete fileWriteResolvers[reqId];
+                    cmd('cmd://file/write?path=' + encodeURIComponent(path) +
-                        resolve({ ok: false, error: 'timeout' });
+                        '&data=' + encodeURIComponent(b64) +
-                    }
+                        '&reqId=' + encodeURIComponent(reqId));
-                }, 30000);
+                    setTimeout(() => {
-            });
+                        if (fileWriteResolvers[reqId]) {
+                            delete fileWriteResolvers[reqId];
+                            resolve({ ok: false, error: 'timeout' });
+                        }
+                    }, 30000);
+                });
+            }
+            return (async () => {
+                const totalChunks = Math.ceil(b64.length / CHUNK);
+                let done = 0;
+                for (let off = 0; off < b64.length; off += CHUNK) {
+                    const piece = b64.slice(off, off + CHUNK);
+                    const ackOk = await new Promise(res => {
+                        fileChunkResolvers[reqId] = res;
+                        cmd('cmd://file/chunk?reqId=' + encodeURIComponent(reqId) +
+                            '&data=' + encodeURIComponent(piece));
+                        setTimeout(() => {
+                            if (fileChunkResolvers[reqId]) {
+                                delete fileChunkResolvers[reqId];
+                                res(false);
+                            }
+                        }, 30000);
+                    });
+                    if (!ackOk) return { ok: false, error: 'chunk transfer failed' };
+                    done++;
+                    if (typeof onProgress === 'function')
+                        onProgress(Math.round(done / totalChunks * 100));
+                }
+                return await new Promise(resolve => {
+                    fileWriteResolvers[reqId] = resolve;
+                    cmd('cmd://file/write-commit?reqId=' + encodeURIComponent(reqId) +
+                        '&path=' + encodeURIComponent(path));
+                    setTimeout(() => {
+                        if (fileWriteResolvers[reqId]) {
+                            delete fileWriteResolvers[reqId];
+                            resolve({ ok: false, error: 'timeout' });
+                        }
+                    }, 30000);
+                });
+            })();
         },
         onFileWriteResult(reqId, ok, err) {
             const r = fileWriteResolvers[reqId];
@@ -10432,14 +10471,19 @@ async function onToggleAutoBackup(ev) {
     }
 }
 
-async function runAutoBackupNow() {
+async function runAutoBackupNow(silent) {
     const cfg = await loadAutoBackupConfig();
-    if (!cfg) return toast('Bridge not available', 'error');
+    if (!cfg) return silent || toast('Bridge not available', 'error');
-    if (!cfg.dir) return toast('Choose a backup folder first', 'warning');
+    if (!cfg.dir) return silent || toast('Choose a backup folder first', 'warning');
-    if (!cfg.hasPwd) return toast('Backup password not set', 'warning');
+    if (!cfg.hasPwd) return silent || toast('Backup password not set', 'warning');
-    if (!state.cryptoKey) return toast('Vault is locked', 'warning');
+    if (!state.cryptoKey) return silent || toast('Vault is locked', 'warning');
 
-    toast('Encrypting backup…');
+    // Manual "Backup now" shows a spinner (big vaults take ~30s). The
+    // scheduled on-unlock run stays silent (no overlay stealing focus).
+    if (!silent) {
+        showBusy('Reading vault…');
+        await new Promise(r => setTimeout(r, 0));
+    }
     try {
         const payload = {
             version: 1,
@@ -10454,7 +10498,12 @@ async function runAutoBackupNow() {
                        })),
             entries: [],
         };
+        let _bkDone = 0;
+        const _bkTotal = state.entries.length;
         for (const e of state.entries) {
+            _bkDone++;
+            if (!silent && _bkTotal > 10 && (_bkDone % 5 === 0 || _bkDone === _bkTotal))
+                updateBusy('Reading vault… ' + _bkDone + '/' + _bkTotal);
             const plain = await decryptPwd(e.encrypted_password, e.iv);
             let plainTotp = '';
             if (e.totp_secret && e.totp_iv) {
@@ -10497,6 +10546,7 @@ async function runAutoBackupNow() {
                 created_at: e.created_at, updated_at: e.updated_at,
             });
         }
+        if (!silent) updateBusy('Encrypting backup…');
         const container = await encryptExportPayload(payload, cfg.pwd);
         const json = JSON.stringify(container, null, 2);
         // Filename: yyyymmdd-HHMMSS for filesystem-sort-friendliness.
@@ -10504,18 +10554,23 @@ async function runAutoBackupNow() {
             .replace(/[-:]/g, '').replace('T', '-').slice(0, 15);
         const fname = AUTO_BACKUP_PREFIX + ts + '.json';
         const path = cfg.dir.replace(/[\\/]+$/, '') + '\\' + fname;
-        const res = await Bridge.writeFile(path, json);
+        if (!silent) updateBusy('Writing file…');
+        const res = await Bridge.writeFile(path, json, pct => {
+            if (!silent) updateBusy('Writing file… ' + pct + '%');
+        });
         if (!res.ok) {
-            toast('Backup failed: ' + (res.error || 'unknown'), 'error');
+            if (!silent) toast('Backup failed: ' + (res.error || 'unknown'), 'error');
             return;
         }
         const now = new Date().toISOString();
         Bridge.setPref(ABK.last, now);
         $('#autoBackupLast').textContent = 'Last run: ' + now.replace('T', ' ').slice(0, 16);
-        toast(payload.entries.length + ' entries backed up');
+        if (!silent) toast(payload.entries.length + ' entries backed up');
         applyAutoBackupRetention(cfg.dir, cfg.keep);
     } catch (err) {
-        toast('Backup failed: ' + (err && err.message ? err.message : err), 'error');
+        if (!silent) toast('Backup failed: ' + (err && err.message ? err.message : err), 'error');
+    } finally {
+        if (!silent) hideBusy();
     }
 }
 
@@ -10543,7 +10598,7 @@ async function runAutoBackupIfDue() {
     const intervalMs = cfg.interval * 24 * 3600 * 1000;
     const last = cfg.last ? Date.parse(cfg.last) : 0;
     if (last && (Date.now() - last) < intervalMs) return;
-    await runAutoBackupNow();
+    await runAutoBackupNow(true);   // silent — no spinner on the scheduled run
 }
 
 // ============================================================
@@ -11430,7 +11485,7 @@ async function init() {
         e.target.value = n;
         Bridge.setPref(ABK.keep, String(n));
     });
-    $('#autoBackupNowBtn').addEventListener('click', runAutoBackupNow);
+    $('#autoBackupNowBtn').addEventListener('click', () => runAutoBackupNow());
 
     $('#settingFavicons').addEventListener('change', e => {
         state.faviconsEnabled = e.target.checked;