feat: auto-regenerate preview on settings change

e2e/settings.spec.ts

@@ -1,5 +1,4 @@
 import { test, expect } from '@playwright/test'
-import { createLandscapePng, uploadTestImage } from './test-helpers'
 
 test.beforeEach(async ({ page }) => {
   await page.goto('/')

src/App.tsx

@@ -1,4 +1,4 @@
-import { useState, useCallback } from 'react';
+import { useState, useCallback, useEffect, useRef } from 'react';
 import JSZip from 'jszip';
 import { PhotoUpload } from './components/PhotoUpload';
 import { PaddingSettingsPanel } from './components/PaddingSettingsPanel';
@@ -67,7 +67,12 @@ export default function App() {
   const [isProcessed, setIsProcessed] = useState(false);
   const [progress, setProgress] = useState(0);
   const [theme, setTheme] = useDarkMode();
-  const [settingsChangedSinceProcess, setSettingsChangedSinceProcess] = useState(false);
+
+  // Ref that always holds the latest handleProcess so the debounce timer
+  // never captures a stale closure.
+  const handleProcessRef = useRef<() => void>(() => {});
+  const autoProcessTimerRef = useRef<ReturnType<typeof setTimeout> | undefined>(undefined);
+  const isInitialMountRef = useRef(true);
 
   const THEME_OPTIONS: { value: Theme; icon: typeof Sun; label: string }[] = [
     { value: 'light', icon: Sun, label: 'Light' },
@@ -116,7 +121,6 @@ export default function App() {
     if (photos.length === 0) return;
     setIsProcessing(true);
     setProgress(0);
-    setSettingsChangedSinceProcess(false);
 
     // Determine target aspect ratio
     let target: number;
@@ -138,6 +142,26 @@ export default function App() {
     setIsProcessed(true);
   };
 
+  // Keep the ref pointing at the latest handleProcess so the debounce
+  // timer always calls the version that closes over fresh state.
+  useEffect(() => {
+    handleProcessRef.current = handleProcess;
+  });
+
+  // Auto-process when settings change (debounced), provided photos are loaded.
+  // photos.length is intentionally omitted from deps to avoid triggering on
+  // photo additions/removals; handleProcess already guards against empty photos.
+  useEffect(() => {
+    if (isInitialMountRef.current) {
+      isInitialMountRef.current = false;
+      return;
+    }
+    if (photos.length === 0) return;
+    clearTimeout(autoProcessTimerRef.current);
+    autoProcessTimerRef.current = setTimeout(() => handleProcessRef.current(), 400);
+    return () => clearTimeout(autoProcessTimerRef.current);
+  }, [settings]); // eslint-disable-line react-hooks/exhaustive-deps
+
   const handleDownloadAll = async () => {
     const processedPhotos = photos.filter(p => p.paddedDataUrl);
     if (processedPhotos.length === 0) return;
@@ -281,7 +305,6 @@ export default function App() {
               defaultSettings={DEFAULT_SETTINGS}
               onChange={s => {
                 setSettings(s);
-                if (isProcessed) setSettingsChangedSinceProcess(true);
                 setIsProcessed(false);
               }}
             />
@@ -305,11 +328,6 @@ export default function App() {
                     </>
                   )}
                 </button>
-                {settingsChangedSinceProcess && (
-                  <p className="text-xs text-amber-600 dark:text-amber-400 text-center mt-2">
-                    Settings changed — re-process to apply
-                  </p>
-                )}
               </div>
             </div>
           </div>

src/__tests__/App.test.tsx

@@ -39,7 +39,7 @@ describe('App', () => {
       addListener: vi.fn(),
       removeListener: vi.fn(),
       dispatchEvent: vi.fn(),
-    })) as any;
+    })) as unknown as MediaQueryList;
   });
 
   afterEach(() => {
@@ -114,7 +114,7 @@ describe('App', () => {
         setTimeout(() => this.onload?.(), 0);
       }
     }
-    global.FileReader = MockFileReader as any;
+    global.FileReader = MockFileReader as unknown as typeof FileReader;
 
     return {
       restore: () => { global.FileReader = origFileReader; },
@@ -204,4 +204,60 @@ describe('App', () => {
 
     restore();
   });
+
+  // --- Auto-process on settings change ---
+  it('does not show "Settings changed" warning (auto-process replaces it)', async () => {
+    const user = userEvent.setup();
+    const mockFile = await setupMocksAndUpload();
+    const { padImageToAspectRatio } = await import('../lib/imageUtils');
+    (padImageToAspectRatio as ReturnType<typeof vi.fn>).mockResolvedValue('data:image/png;base64,padded');
+    const { restore } = setupUploadMocks();
+
+    render(<App />);
+
+    // Upload and process
+    const input = document.querySelector('input[type="file"]') as HTMLInputElement;
+    fireEvent.change(input, { target: { files: [mockFile] } });
+    await waitFor(() => expect(screen.getByText(/1 photo/)).toBeInTheDocument());
+    await user.click(screen.getByText('Process Images').closest('button')!);
+    await waitFor(() => expect(screen.getByText('Download All as ZIP')).toBeInTheDocument());
+
+    // Change a setting – the old warning must never appear
+    const resetButton = screen.getByTitle('Reset to defaults');
+    await user.click(resetButton);
+    expect(screen.queryByText(/re-process to apply/i)).not.toBeInTheDocument();
+
+    restore();
+  });
+
+  it('auto-processes after a settings change when photos are loaded', async () => {
+    const user = userEvent.setup();
+    const mockFile = await setupMocksAndUpload();
+    const { padImageToAspectRatio } = await import('../lib/imageUtils');
+    (padImageToAspectRatio as ReturnType<typeof vi.fn>).mockResolvedValue('data:image/png;base64,padded');
+    const { restore } = setupUploadMocks();
+
+    render(<App />);
+
+    // Upload and do the initial manual process
+    const input = document.querySelector('input[type="file"]') as HTMLInputElement;
+    fireEvent.change(input, { target: { files: [mockFile] } });
+    await waitFor(() => expect(screen.getByText(/1 photo/)).toBeInTheDocument());
+    await user.click(screen.getByText('Process Images').closest('button')!);
+    await waitFor(() => expect(screen.getByText('Download All as ZIP')).toBeInTheDocument());
+
+    // Simulate a settings change by switching the output format (JPEG ≠ default PNG)
+    await user.click(screen.getByRole('button', { name: 'jpeg' }));
+
+    // Download All disappears immediately (isProcessed reset to false)
+    expect(screen.queryByText('Download All as ZIP')).not.toBeInTheDocument();
+
+    // After the debounce fires, auto-process re-runs and Download All reappears
+    await waitFor(
+      () => expect(screen.getByText('Download All as ZIP')).toBeInTheDocument(),
+      { timeout: 3000 },
+    );
+
+    restore();
+  }, 5000);
 });

src/__tests__/PhotoGrid.test.tsx

@@ -1,4 +1,4 @@
-import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { describe, it, expect, vi, afterEach } from 'vitest';
 import { render, screen, fireEvent, act } from '@testing-library/react';
 import { PhotoGrid } from '../components/PhotoGrid';
 import type { UploadedPhoto } from '../types';
@@ -70,7 +70,7 @@ describe('PhotoGrid', () => {
     const clickSpy = vi.fn()
     const createElementSpy = vi.spyOn(document, 'createElement').mockImplementation((tag: string) => {
       if (tag === 'a') {
-        return { href: '', download: '', click: clickSpy } as any
+        return { href: '', download: '', click: clickSpy } as unknown as HTMLAnchorElement
       }
       return originalCreateElement(tag)
     })
@@ -116,13 +116,13 @@ describe('PhotoGrid', () => {
     })
     globalThis.ClipboardItem = class {
       constructor(public items: Record<string, Blob>) {}
-    } as any
+    } as unknown as typeof ClipboardItem
 
     const pngBlob = new Blob(['px'], { type: 'image/png' })
     const mockFetch = vi.fn().mockResolvedValue({
       blob: () => Promise.resolve(pngBlob),
     })
-    window.fetch = mockFetch as any
+    window.fetch = mockFetch as unknown as typeof fetch
 
     const photos = [
       makePhoto({ id: 'p1', paddedDataUrl: 'data:image/png;base64,padded' }),
@@ -160,7 +160,7 @@ describe('PhotoGrid', () => {
           set(v: string) { downloadFilename = v },
           get() { return downloadFilename },
         })
-        return anchor as any
+        return anchor as unknown as HTMLAnchorElement
       }
       return originalCreateElement(tag)
     })
@@ -187,7 +187,7 @@ describe('PhotoGrid', () => {
           set(v: string) { downloadFilename = v },
           get() { return downloadFilename },
         })
-        return anchor as any
+        return anchor as unknown as HTMLAnchorElement
       }
       return originalCreateElement(tag)
     })

src/__tests__/heicUtils.test.ts

@@ -117,7 +117,7 @@ describe('convertHeicToJpeg', () => {
     }])
     const mockCanvas = makeMockCanvas()
     createElementSpy = vi.spyOn(document, 'createElement').mockImplementation((tag: string) => {
-      if (tag === 'canvas') return mockCanvas as any
+      if (tag === 'canvas') return mockCanvas as unknown as HTMLCanvasElement
       return originalCreateElement(tag)
     })
   })
@@ -150,7 +150,7 @@ describe('convertHeicToJpeg', () => {
     createElementSpy.mockRestore()
     const mockCanvas = makeMockCanvas(null)
     createElementSpy = vi.spyOn(document, 'createElement').mockImplementation((tag: string) => {
-      if (tag === 'canvas') return mockCanvas as any
+      if (tag === 'canvas') return mockCanvas as unknown as HTMLCanvasElement
       return originalCreateElement(tag)
     })
 
@@ -173,7 +173,7 @@ describe('processFilesForHeic', () => {
     }])
     const mockCanvas = makeMockCanvas()
     createElementSpy = vi.spyOn(document, 'createElement').mockImplementation((tag: string) => {
-      if (tag === 'canvas') return mockCanvas as any
+      if (tag === 'canvas') return mockCanvas as unknown as HTMLCanvasElement
       return originalCreateElement(tag)
     })
   })

src/__tests__/imageUtils.test.ts

@@ -1,6 +1,6 @@
 import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
 import { findMaxAspectRatio, getImageDimensions, padImageToAspectRatio, drawPatternFill, drawWatermark, getWatermarkPosition } from '../lib/imageUtils'
-import type { UploadedPhoto, PaddingSettings, PatternSettings, WatermarkSettings, WatermarkPosition } from '../types'
+import type { UploadedPhoto, PaddingSettings, PatternSettings, WatermarkSettings } from '../types'
 
 function makePhoto(width: number, height: number, overrides?: Partial<UploadedPhoto>): UploadedPhoto {
   return {
@@ -92,7 +92,7 @@ function installCanvasMocks() {
 
   HTMLCanvasElement.prototype.getContext = vi.fn(() => mockCtx) as unknown as typeof HTMLCanvasElement.prototype.getContext
   HTMLCanvasElement.prototype.toDataURL = vi.fn(
-    (type?: string, _quality?: unknown) => `data:${type ?? 'image/png'};base64,MOCK`
+    (type?: string) => `data:${type ?? 'image/png'};base64,MOCK`
   )
 }
 
@@ -108,13 +108,12 @@ function installImageMock(naturalWidth = 800, naturalHeight = 600) {
     onerror: ((err: unknown) => void) | null = null
 
     constructor() {
-      const self = this
       // Auto-fire onload on next microtask after src is set
       Object.defineProperty(this, 'src', {
-        get: () => self._src,
-        set(value: string) {
-          self._src = value
-          queueMicrotask(() => self.onload?.())
+        get: () => this._src,
+        set: (value: string) => {
+          this._src = value
+          queueMicrotask(() => this.onload?.())
         },
       })
     }
@@ -288,15 +287,15 @@ describe('padImageToAspectRatio', () => {
   it('outputs webp format with quality', async () => {
     const photo = makePhoto(600, 600, { dataUrl: 'data:img' })
     const settings = defaultSettings({ outputFormat: 'webp', outputQuality: 0.9 })
-    const result = await padImageToAspectRatio(photo, 2, settings)
+    await padImageToAspectRatio(photo, 2, settings)
 
     expect(HTMLCanvasElement.prototype.toDataURL).toHaveBeenCalledWith('image/webp', 0.9)
   })
 
   it('outputs png format without quality parameter', async () => {
     const photo = makePhoto(600, 600, { dataUrl: 'data:img' })
     const settings = defaultSettings({ outputFormat: 'png' })
-    const result = await padImageToAspectRatio(photo, 2, settings)
+    await padImageToAspectRatio(photo, 2, settings)
 
     expect(HTMLCanvasElement.prototype.toDataURL).toHaveBeenCalledWith('image/png', undefined)
   })

src/__tests__/useDarkMode.test.ts

@@ -34,12 +34,12 @@ describe('useDarkMode', () => {
       mockListeners.push(...listeners);
       // Keep reference so listeners added later are captured
       const origAddEventListener = mql.addEventListener as ReturnType<typeof vi.fn>;
-      (mql as any).addEventListener = vi.fn((_event: string, handler: (e: { matches: boolean }) => void) => {
+      (mql as unknown as Record<string, unknown>).addEventListener = vi.fn((_event: string, handler: (e: { matches: boolean }) => void) => {
         mockListeners.push(handler);
         origAddEventListener(_event, handler);
       });
       return mql;
-    }) as any;
+    }) as unknown as typeof window.matchMedia;
   });
 
   afterEach(() => {
@@ -104,7 +104,7 @@ describe('useDarkMode', () => {
     window.matchMedia = vi.fn(() => {
       const { mql } = createMatchMedia(true);
       return mql;
-    }) as any;
+    }) as unknown as typeof window.matchMedia;
     const { result } = renderHook(() => useDarkMode());
     expect(result.current[0]).toBe('system');
     expect(result.current[2]).toBe(true);