fix: harden html responses and cache chat sidebar data

Use strict template response handling and sanitized template user context, then add an in-process conversation archive cache with mutation-driven invalidation for chat sidebar renders.

html-router/src/html_state.rs

@@ -1,9 +1,13 @@
+use common::storage::types::conversation::Conversation;
 use common::storage::{db::SurrealDbClient, store::StorageManager};
 use common::utils::embedding::EmbeddingProvider;
 use common::utils::template_engine::{ProvidesTemplateEngine, TemplateEngine};
 use common::{create_template_engine, storage::db::ProvidesDb, utils::config::AppConfig};
 use retrieval_pipeline::{reranking::RerankerPool, RetrievalStrategy};
+use std::collections::HashMap;
 use std::sync::Arc;
+use std::time::{Duration, Instant};
+use tokio::sync::RwLock;
 use tracing::debug;
 
 use crate::{OpenAIClientType, SessionStoreType};
@@ -18,8 +22,17 @@ pub struct HtmlState {
     pub storage: StorageManager,
     pub reranker_pool: Option<Arc<RerankerPool>>,
     pub embedding_provider: Arc<EmbeddingProvider>,
+    conversation_archive_cache: Arc<RwLock<HashMap<String, ConversationArchiveCacheEntry>>>,
 }
 
+#[derive(Clone)]
+struct ConversationArchiveCacheEntry {
+    conversations: Vec<Conversation>,
+    expires_at: Instant,
+}
+
+const CONVERSATION_ARCHIVE_CACHE_TTL: Duration = Duration::from_secs(30);
+
 impl HtmlState {
     pub async fn new_with_resources(
         db: Arc<SurrealDbClient>,
@@ -44,6 +57,7 @@ impl HtmlState {
             storage,
             reranker_pool,
             embedding_provider,
+            conversation_archive_cache: Arc::new(RwLock::new(HashMap::new())),
         })
     }
 
@@ -54,6 +68,38 @@ impl HtmlState {
             .and_then(|value| value.parse().ok())
             .unwrap_or(RetrievalStrategy::Default)
     }
+
+    pub async fn get_cached_conversation_archive(
+        &self,
+        user_id: &str,
+    ) -> Option<Vec<Conversation>> {
+        let cache = self.conversation_archive_cache.read().await;
+        let entry = cache.get(user_id)?;
+        if entry.expires_at <= Instant::now() {
+            return None;
+        }
+        Some(entry.conversations.clone())
+    }
+
+    pub async fn set_cached_conversation_archive(
+        &self,
+        user_id: &str,
+        conversations: Vec<Conversation>,
+    ) {
+        let mut cache = self.conversation_archive_cache.write().await;
+        cache.insert(
+            user_id.to_string(),
+            ConversationArchiveCacheEntry {
+                conversations,
+                expires_at: Instant::now() + CONVERSATION_ARCHIVE_CACHE_TTL,
+            },
+        );
+    }
+
+    pub async fn invalidate_conversation_archive_cache(&self, user_id: &str) {
+        let mut cache = self.conversation_archive_cache.write().await;
+        cache.remove(user_id);
+    }
 }
 impl ProvidesDb for HtmlState {
     fn db(&self) -> &Arc<SurrealDbClient> {