feat: strengthen backup and mobile workflows

frontend/src/lib/backup-preflight-state.test.ts

@@ -0,0 +1,39 @@
+import { describe, expect, it } from 'vitest'
+import { backupFileSnapshot, isCurrentBackupSnapshot, shouldCommitBackupPreflight } from './backup-preflight-state'
+
+describe('backup preflight identity', () => {
+  it('rejects a preflight result after the selected file changes even when the old request finishes last', () => {
+    const oldFile = new File(['old'], 'old.zip', { lastModified: 10 })
+    const newFile = new File(['new'], 'new.zip', { lastModified: 20 })
+    const started = backupFileSnapshot(oldFile, 'merge')
+
+    expect(isCurrentBackupSnapshot(started, newFile, 'merge')).toBe(false)
+  })
+
+  it('does not let a token for one filename authorize another file with matching metadata', () => {
+    const first = new File(['same'], 'first.zip', { lastModified: 10 })
+    const second = new File(['same'], 'second.zip', { lastModified: 10 })
+
+    expect(isCurrentBackupSnapshot(backupFileSnapshot(first, 'merge'), second, 'merge')).toBe(false)
+  })
+
+  it('invalidates a preflight when restore mode changes', () => {
+    const file = new File(['zip'], 'backup.zip', { lastModified: 10 })
+
+    expect(isCurrentBackupSnapshot(backupFileSnapshot(file, 'merge'), file, 'replace')).toBe(false)
+  })
+
+  it('rejects an older generation even when its file snapshot still matches', () => {
+    const file = new File(['zip'], 'backup.zip', { lastModified: 10 })
+    expect(shouldCommitBackupPreflight(1, 2, backupFileSnapshot(file, 'merge'), file, 'merge')).toBe(false)
+    expect(shouldCommitBackupPreflight(2, 2, backupFileSnapshot(file, 'merge'), file, 'merge')).toBe(true)
+  })
+
+  it('binds identity to the exact File object as well as name size and modified time', () => {
+    const first = new File(['same'], 'backup.zip', { lastModified: 10 })
+    const replacement = new File(['same'], 'backup.zip', { lastModified: 10 })
+
+    expect(isCurrentBackupSnapshot(backupFileSnapshot(first, 'merge'), replacement, 'merge')).toBe(false)
+    expect(isCurrentBackupSnapshot(backupFileSnapshot(first, 'merge'), first, 'merge')).toBe(true)
+  })
+})

frontend/src/lib/backup-preflight-state.ts

@@ -0,0 +1,36 @@
+import type { BackupMode } from '../api'
+
+export type BackupFileSnapshot = {
+  file: File
+  name: string
+  size: number
+  lastModified: number
+  mode: BackupMode
+}
+
+export function backupFileSnapshot(file: File, mode: BackupMode): BackupFileSnapshot {
+  return { file, name: file.name, size: file.size, lastModified: file.lastModified, mode }
+}
+
+export function isCurrentBackupSnapshot(snapshot: BackupFileSnapshot, file: File | null, mode: BackupMode) {
+  return Boolean(file)
+    && snapshot.file === file
+    && snapshot.name === file!.name
+    && snapshot.size === file!.size
+    && snapshot.lastModified === file!.lastModified
+    && snapshot.mode === mode
+}
+
+export function shouldCommitBackupPreflight(
+  generation: number,
+  currentGeneration: number,
+  snapshot: BackupFileSnapshot,
+  file: File | null,
+  mode: BackupMode,
+) {
+  return generation === currentGeneration && isCurrentBackupSnapshot(snapshot, file, mode)
+}
+
+export function isLegacyBackup(file: File) {
+  return !file.name.toLowerCase().endsWith('.zip')
+}

frontend/src/lib/list-purge.test.ts

@@ -1,15 +0,0 @@
-import { describe, expect, it } from 'vitest'
-import { nextDialogFocusIndex } from './list-purge'
-
-describe('archived list purge dialog behavior', () => {
-  it('wraps Tab focus between the cancel and destructive actions', () => {
-    expect(nextDialogFocusIndex(0, 2, true)).toBe(1)
-    expect(nextDialogFocusIndex(1, 2, false)).toBe(0)
-  })
-
-  it('leaves focus alone while moving between interior controls', () => {
-    expect(nextDialogFocusIndex(1, 3, true)).toBeNull()
-    expect(nextDialogFocusIndex(1, 3, false)).toBeNull()
-    expect(nextDialogFocusIndex(0, 0, false)).toBeNull()
-  })
-})

frontend/src/lib/list-purge.ts

@@ -1,6 +0,0 @@
-export function nextDialogFocusIndex(currentIndex: number, controlCount: number, shiftKey: boolean) {
-  if (controlCount < 2) return null
-  if (shiftKey && currentIndex === 0) return controlCount - 1
-  if (!shiftKey && currentIndex === controlCount - 1) return 0
-  return null
-}