Cache AI Page Link summary (#3106)

Co-authored-by: Samy Pessé <samypesse@gmail.com>

.changeset/chilly-snakes-sell.md

@@ -0,0 +1,5 @@
+---
+"gitbook": patch
+---
+
+Cache AI Page Link summary

packages/gitbook/src/components/Adaptive/AIPageLinkSummary.tsx

@@ -3,11 +3,32 @@ import { useLanguage } from '@/intl/client';
 import { t } from '@/intl/translate';
 import { Icon } from '@gitbook/icons';
 import { useEffect, useState } from 'react';
+import { create } from 'zustand';
 import { useVisitedPages } from '../Insights';
 import { usePageContext } from '../PageContext';
 import { Loading } from '../primitives';
 import { streamLinkPageSummary } from './server-actions/streamLinkPageSummary';
 
+const useSummaries = create<{
+    cache: Map<string, string>;
+    setSummary: (key: string, summary: string) => void;
+}>((set) => ({
+    cache: new Map(),
+    setSummary: (key, summary) =>
+        set((state) => {
+            const newCache = new Map(state.cache);
+            newCache.set(key, summary);
+            return { cache: newCache };
+        }),
+}));
+
+/**
+ * Get a unique cache key for a page summary
+ */
+function getCacheKey(targetSpaceId: string, targetPageId: string): string {
+    return `${targetSpaceId}:${targetPageId}`;
+}
+
 /**
  * Summarise a page's content for use in a link preview
  */
@@ -21,15 +42,26 @@ export function AIPageLinkSummary(props: {
     const { targetSpaceId, targetPageId, linkPreview, linkTitle, showTrademark = true } = props;
 
     const currentPage = usePageContext();
-
     const language = useLanguage();
     const visitedPages = useVisitedPages((state) => state.pages);
-    const [highlight, setHighlight] = useState('');
+    const [summary, setSummary] = useState('');
+    const cacheKey = getCacheKey(targetSpaceId, targetPageId);
+    const { cachedSummary, setCachedSummary } = useSummaries((state) => {
+        return {
+            cachedSummary: state.cache.get(cacheKey) ?? '',
+            setCachedSummary: state.setSummary,
+        };
+    });
 
     useEffect(() => {
         let canceled = false;
 
-        setHighlight('');
+        setSummary('');
+
+        if (cachedSummary) {
+            setSummary(cachedSummary);
+            return;
+        }
 
         (async () => {
             const stream = await streamLinkPageSummary({
@@ -43,9 +75,16 @@ export function AIPageLinkSummary(props: {
                 visitedPages,
             });
 
+            let generatedSummary = '';
             for await (const highlight of stream) {
                 if (canceled) return;
-                setHighlight(highlight ?? '');
+                generatedSummary = highlight ?? '';
+                setSummary(generatedSummary);
+            }
+
+            // Cache the complete summary
+            if (generatedSummary) {
+                setCachedSummary(cacheKey, generatedSummary);
             }
         })();
 
@@ -61,6 +100,9 @@ export function AIPageLinkSummary(props: {
         linkPreview,
         linkTitle,
         visitedPages,
+        cachedSummary,
+        cacheKey,
+        setCachedSummary,
     ]);
 
     const shimmerBlocks = [
@@ -76,14 +118,14 @@ export function AIPageLinkSummary(props: {
         <div className="flex flex-col gap-1">
             <div className="flex w-screen items-center gap-1 font-semibold text-tint text-xs uppercase leading-tight tracking-wide">
                 {showTrademark ? (
-                    <Loading className="size-4" busy={!highlight || highlight.length === 0} />
+                    <Loading className="size-4" busy={!summary || summary.length === 0} />
                 ) : (
                     <Icon icon="sparkle" className="size-3" />
                 )}
                 <h6 className="text-tint">{t(language, 'link_tooltip_ai_summary')}</h6>
             </div>
-            {highlight.length > 0 ? (
-                <p className="animate-fadeIn">{highlight}</p>
+            {summary.length > 0 ? (
+                <p className="animate-fadeIn">{summary}</p>
             ) : (
                 <div className="mt-2 flex flex-wrap gap-2">
                     {shimmerBlocks.map((block, index) => (
@@ -94,7 +136,7 @@ export function AIPageLinkSummary(props: {
                     ))}
                 </div>
             )}
-            {highlight.length > 0 ? (
+            {summary.length > 0 ? (
                 <div className="animate-fadeIn text-tint-subtle text-xs">
                     {t(language, 'link_tooltip_ai_summary_description')}
                 </div>