Add PersistenceQueue mid-flight flush test

src/store/middleware/persistenceMiddleware.test.ts

@@ -0,0 +1,103 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+import { PersistenceQueue } from './persistenceMiddleware'
+
+const { putMock, deleteMock, syncMock } = vi.hoisted(() => ({
+  putMock: vi.fn<[string, unknown], Promise<void>>(),
+  deleteMock: vi.fn<[string, string], Promise<void>>(),
+  syncMock: vi.fn<[string, string, unknown, string], Promise<void>>()
+}))
+
+vi.mock('@/lib/db', () => ({
+  db: {
+    put: putMock,
+    delete: deleteMock
+  }
+}))
+
+vi.mock('./flaskSync', () => ({
+  syncToFlask: syncMock
+}))
+
+const nextTick = () => new Promise(resolve => setTimeout(resolve, 0))
+
+const waitFor = async (assertion: () => void, attempts = 5) => {
+  let lastError: unknown
+
+  for (let i = 0; i < attempts; i += 1) {
+    await nextTick()
+
+    try {
+      assertion()
+      return
+    } catch (error) {
+      lastError = error
+    }
+  }
+
+  throw lastError
+}
+
+const createControlledPromise = () => {
+  let resolve: () => void
+
+  const promise = new Promise<void>((resolvePromise) => {
+    resolve = resolvePromise
+  })
+
+  return {
+    promise,
+    resolve: resolve!
+  }
+}
+
+describe('PersistenceQueue', () => {
+  beforeEach(() => {
+    putMock.mockReset()
+    deleteMock.mockReset()
+    syncMock.mockReset()
+    syncMock.mockResolvedValue(undefined)
+  })
+
+  afterEach(() => {
+    vi.useRealTimers()
+  })
+
+  it('flushes new operations enqueued while processing after the first batch finishes', async () => {
+    const queue = new PersistenceQueue()
+    const controlled = createControlledPromise()
+
+    putMock
+      .mockReturnValueOnce(controlled.promise)
+      .mockResolvedValueOnce(undefined)
+
+    queue.enqueue({
+      type: 'put',
+      storeName: 'files',
+      key: 'file-1',
+      value: { id: 'file-1' },
+      timestamp: Date.now(),
+    }, 0)
+
+    await waitFor(() => {
+      expect(putMock).toHaveBeenCalledTimes(1)
+    })
+
+    queue.enqueue({
+      type: 'put',
+      storeName: 'files',
+      key: 'file-2',
+      value: { id: 'file-2' },
+      timestamp: Date.now(),
+    }, 0)
+
+    await nextTick()
+    expect(putMock).toHaveBeenCalledTimes(1)
+
+    controlled.resolve()
+
+    await waitFor(() => {
+      expect(putMock).toHaveBeenCalledTimes(2)
+    })
+  })
+})

src/store/middleware/persistenceMiddleware.ts

@@ -38,7 +38,7 @@ type PendingOperation = {
   timestamp: number
 }
 
-class PersistenceQueue {
+export class PersistenceQueue {
   private queue: Map<string, PendingOperation> = new Map()
   private processing = false
   private debounceTimers: Map<string, ReturnType<typeof setTimeout>> = new Map()
@@ -97,6 +97,9 @@ class PersistenceQueue {
       }
     } finally {
       this.processing = false
+      if (this.queue.size > 0) {
+        await this.processQueue()
+      }
     }
   }