feat(highlights): add optional session cache with TTL

- Add in-memory cache with 60s TTL for article/url/author queries
- Check cache before network fetch to reduce redundant queries
- Support force flag to bypass cache when needed
- Stream cached results through onHighlight callback for consistency

src/services/highlights/cache.ts

@@ -0,0 +1,96 @@
+import { Highlight } from '../../types/highlights'
+
+interface CacheEntry {
+  highlights: Highlight[]
+  timestamp: number
+}
+
+/**
+ * Simple in-memory session cache for highlight queries with TTL
+ */
+class HighlightCache {
+  private cache = new Map<string, CacheEntry>()
+  private ttlMs = 60000 // 60 seconds
+
+  /**
+   * Generate cache key for article coordinate
+   */
+  articleKey(coordinate: string): string {
+    return `article:${coordinate}`
+  }
+
+  /**
+   * Generate cache key for URL
+   */
+  urlKey(url: string): string {
+    // Normalize URL for consistent caching
+    try {
+      const normalized = new URL(url)
+      normalized.hash = '' // Remove hash
+      return `url:${normalized.toString()}`
+    } catch {
+      return `url:${url}`
+    }
+  }
+
+  /**
+   * Generate cache key for author pubkey
+   */
+  authorKey(pubkey: string): string {
+    return `author:${pubkey}`
+  }
+
+  /**
+   * Get cached highlights if not expired
+   */
+  get(key: string): Highlight[] | null {
+    const entry = this.cache.get(key)
+    if (!entry) return null
+
+    const now = Date.now()
+    if (now - entry.timestamp > this.ttlMs) {
+      this.cache.delete(key)
+      return null
+    }
+
+    return entry.highlights
+  }
+
+  /**
+   * Store highlights in cache
+   */
+  set(key: string, highlights: Highlight[]): void {
+    this.cache.set(key, {
+      highlights,
+      timestamp: Date.now()
+    })
+  }
+
+  /**
+   * Clear specific cache entry
+   */
+  clear(key: string): void {
+    this.cache.delete(key)
+  }
+
+  /**
+   * Clear all cache entries
+   */
+  clearAll(): void {
+    this.cache.clear()
+  }
+
+  /**
+   * Get cache stats
+   */
+  stats(): { size: number; keys: string[] } {
+    return {
+      size: this.cache.size,
+      keys: Array.from(this.cache.keys())
+    }
+  }
+}
+
+// Singleton instance
+export const highlightCache = new HighlightCache()
+

src/services/highlights/fetchByAuthor.ts

@@ -6,13 +6,28 @@ import { UserSettings } from '../settingsService'
 import { rebroadcastEvents } from '../rebroadcastService'
 import { KINDS } from '../../config/kinds'
 import { queryEvents } from '../dataFetch'
+import { highlightCache } from './cache'
 
 export const fetchHighlights = async (
   relayPool: RelayPool,
   pubkey: string,
   onHighlight?: (highlight: Highlight) => void,
-  settings?: UserSettings
+  settings?: UserSettings,
+  force = false
 ): Promise<Highlight[]> => {
+  // Check cache first unless force refresh
+  if (!force) {
+    const cacheKey = highlightCache.authorKey(pubkey)
+    const cached = highlightCache.get(cacheKey)
+    if (cached) {
+      console.log(`📌 Using cached highlights for author (${cached.length} items)`)
+      // Stream cached highlights if callback provided
+      if (onHighlight) {
+        cached.forEach(h => onHighlight(h))
+      }
+      return cached
+    }
+  }
   try {
     const seenIds = new Set<string>()
     const rawEvents: NostrEvent[] = await queryEvents(
@@ -37,7 +52,13 @@ export const fetchHighlights = async (
 
     const uniqueEvents = dedupeHighlights(rawEvents)
     const highlights = uniqueEvents.map(eventToHighlight)
-    return sortHighlights(highlights)
+    const sorted = sortHighlights(highlights)
+    
+    // Cache the results
+    const cacheKey = highlightCache.authorKey(pubkey)
+    highlightCache.set(cacheKey, sorted)
+    
+    return sorted
   } catch {
     return []
   }

src/services/highlights/fetchForArticle.ts

@@ -6,14 +6,29 @@ import { eventToHighlight, dedupeHighlights, sortHighlights } from '../highlight
 import { UserSettings } from '../settingsService'
 import { rebroadcastEvents } from '../rebroadcastService'
 import { queryEvents } from '../dataFetch'
+import { highlightCache } from './cache'
 
 export const fetchHighlightsForArticle = async (
   relayPool: RelayPool,
   articleCoordinate: string,
   eventId?: string,
   onHighlight?: (highlight: Highlight) => void,
-  settings?: UserSettings
+  settings?: UserSettings,
+  force = false
 ): Promise<Highlight[]> => {
+  // Check cache first unless force refresh
+  if (!force) {
+    const cacheKey = highlightCache.articleKey(articleCoordinate)
+    const cached = highlightCache.get(cacheKey)
+    if (cached) {
+      console.log(`📌 Using cached highlights for article (${cached.length} items)`)
+      // Stream cached highlights if callback provided
+      if (onHighlight) {
+        cached.forEach(h => onHighlight(h))
+      }
+      return cached
+    }
+  }
   try {
     const seenIds = new Set<string>()
     const onEvent = (event: NostrEvent) => {
@@ -41,7 +56,13 @@ export const fetchHighlightsForArticle = async (
 
     const uniqueEvents = dedupeHighlights(rawEvents)
     const highlights: Highlight[] = uniqueEvents.map(eventToHighlight)
-    return sortHighlights(highlights)
+    const sorted = sortHighlights(highlights)
+    
+    // Cache the results
+    const cacheKey = highlightCache.articleKey(articleCoordinate)
+    highlightCache.set(cacheKey, sorted)
+    
+    return sorted
   } catch {
     return []
   }

src/services/highlights/fetchForUrl.ts

@@ -6,13 +6,28 @@ import { eventToHighlight, dedupeHighlights, sortHighlights } from '../highlight
 import { UserSettings } from '../settingsService'
 import { rebroadcastEvents } from '../rebroadcastService'
 import { queryEvents } from '../dataFetch'
+import { highlightCache } from './cache'
 
 export const fetchHighlightsForUrl = async (
   relayPool: RelayPool,
   url: string,
   onHighlight?: (highlight: Highlight) => void,
-  settings?: UserSettings
+  settings?: UserSettings,
+  force = false
 ): Promise<Highlight[]> => {
+  // Check cache first unless force refresh
+  if (!force) {
+    const cacheKey = highlightCache.urlKey(url)
+    const cached = highlightCache.get(cacheKey)
+    if (cached) {
+      console.log(`📌 Using cached highlights for URL (${cached.length} items)`)
+      // Stream cached highlights if callback provided
+      if (onHighlight) {
+        cached.forEach(h => onHighlight(h))
+      }
+      return cached
+    }
+  }
   try {
     const seenIds = new Set<string>()
     const rawEvents: NostrEvent[] = await queryEvents(
@@ -38,7 +53,13 @@ export const fetchHighlightsForUrl = async (
 
     const uniqueEvents = dedupeHighlights(rawEvents)
     const highlights: Highlight[] = uniqueEvents.map(eventToHighlight)
-    return sortHighlights(highlights)
+    const sorted = sortHighlights(highlights)
+    
+    // Cache the results
+    const cacheKey = highlightCache.urlKey(url)
+    highlightCache.set(cacheKey, sorted)
+    
+    return sorted
   } catch (err) {
     console.error('Error fetching highlights for URL:', err)
     return []