feat: Add Download type and document download field, unify preview zoom styling

frontend/src/preview/PreviewContext.tsx

@@ -1,4 +1,4 @@
-import React, { createContext, useContext, useState, useCallback, useMemo, useEffect } from 'react';
+import React, { createContext, useContext, useState, useCallback, useMemo, useRef } from 'react';
 import PreviewZoomOverlay from '../detail/PreviewZoomOverlay';
 import type { Document } from '../types/documents';
 import type { Identifier } from '../types/identifiers';
@@ -20,21 +20,26 @@ export const usePreviewContext = () => {
 
 interface PreviewProviderProps {
     children: React.ReactNode;
-    ensureDownloadUrl?: (docId: Identifier) => Promise<any>;
     onNavigate?: (documentId: Identifier) => void;
 }
 
-export const PreviewProvider: React.FC<PreviewProviderProps> = ({ children, ensureDownloadUrl, onNavigate }) => {
+export const PreviewProvider: React.FC<PreviewProviderProps> = ({ children, onNavigate }) => {
     const [previewDoc, setPreviewDoc] = useState<Document | null>(null);
-    const [previewUrl, setPreviewUrl] = useState<string | null>(null);
+    const lastFocusedElement = useRef<HTMLElement | null>(null);
 
     const openPreview = useCallback((doc: Document) => {
+        if (!lastFocusedElement.current) {
+            lastFocusedElement.current = document.activeElement as HTMLElement;
+        }
         setPreviewDoc(doc);
     }, []);
 
     const closePreview = useCallback(() => {
         setPreviewDoc(null);
-        setPreviewUrl(null);
+        if (lastFocusedElement.current) {
+            lastFocusedElement.current.focus();
+            lastFocusedElement.current = null;
+        }
     }, []);
 
     const handleMaximize = useCallback(() => {
@@ -44,46 +49,6 @@ export const PreviewProvider: React.FC<PreviewProviderProps> = ({ children, ensu
         }
     }, [previewDoc, onNavigate, closePreview]);
 
-    useEffect(() => {
-        if (!previewDoc) {
-            setPreviewUrl(null);
-            return;
-        }
-
-        let cancelled = false;
-        if (ensureDownloadUrl) {
-            ensureDownloadUrl(previewDoc.id)
-                .then((entry) => {
-                    if (!cancelled && entry?.url) {
-                        setPreviewUrl(entry.url);
-                    }
-                })
-                .catch(() => {
-                    if (!cancelled) {
-                        setPreviewUrl(null);
-                    }
-                });
-        }
-
-        return () => {
-            cancelled = true;
-        };
-    }, [previewDoc, ensureDownloadUrl]);
-
-    const overlayDocument = useMemo(() => {
-        if (!previewDoc || !previewUrl) {
-            return previewDoc;
-        }
-        return {
-            ...previewDoc,
-            documentLink: {
-                url: previewUrl,
-                alt: previewDoc.title,
-                mimeType: previewDoc.mime_type,
-            },
-        };
-    }, [previewDoc, previewUrl]);
-
     const value = useMemo(() => ({
         openPreview,
         closePreview,
@@ -93,10 +58,10 @@ export const PreviewProvider: React.FC<PreviewProviderProps> = ({ children, ensu
         <PreviewContext.Provider value={value}>
             {children}
             <PreviewZoomOverlay
-                open={Boolean(previewUrl)}
+                open={Boolean(previewDoc)}
                 onClose={closePreview}
                 onMaximize={onNavigate ? handleMaximize : undefined}
-                document={overlayDocument}
+                document={previewDoc}
             />
         </PreviewContext.Provider>
     );