ux(explore): preserve posts across navigations; seed from cache; merge streamed + final

src/services/exploreCache.ts

@@ -0,0 +1,42 @@
+import { NostrEvent } from 'nostr-tools'
+
+export interface CachedBlogPostPreview {
+  event: NostrEvent
+  title: string
+  summary?: string
+  image?: string
+  published?: number
+  author: string
+}
+
+type CacheValue = {
+  posts: CachedBlogPostPreview[]
+  timestamp: number
+}
+
+const exploreCache = new Map<string, CacheValue>() // key: pubkey
+
+export function getCachedPosts(pubkey: string): CachedBlogPostPreview[] | null {
+  const entry = exploreCache.get(pubkey)
+  if (!entry) return null
+  return entry.posts
+}
+
+export function setCachedPosts(pubkey: string, posts: CachedBlogPostPreview[]): void {
+  exploreCache.set(pubkey, { posts, timestamp: Date.now() })
+}
+
+export function upsertCachedPost(pubkey: string, post: CachedBlogPostPreview): CachedBlogPostPreview[] {
+  const current = exploreCache.get(pubkey)?.posts || []
+  const byId = new Map(current.map(p => [p.event.id, p]))
+  byId.set(post.event.id, post)
+  const merged = Array.from(byId.values()).sort((a, b) => {
+    const ta = a.published || a.event.created_at
+    const tb = b.published || b.event.created_at
+    return tb - ta
+  })
+  setCachedPosts(pubkey, merged)
+  return merged
+}
+
+