feat(conversations): add search endpoint — M1-006 (#299)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

packages/brain/src/conversations.ts

@@ -1,4 +1,4 @@
-import { eq, and, asc, desc, type Db, conversations, messages } from '@mosaic/db';
+import { eq, and, asc, desc, ilike, type Db, conversations, messages } from '@mosaic/db';
 
 /** Maximum number of conversations returned per list query. */
 const MAX_CONVERSATIONS = 200;
@@ -10,6 +10,15 @@ export type NewConversation = typeof conversations.$inferInsert;
 export type Message = typeof messages.$inferSelect;
 export type NewMessage = typeof messages.$inferInsert;
 
+export interface MessageSearchResult {
+  messageId: string;
+  conversationId: string;
+  conversationTitle: string | null;
+  role: 'user' | 'assistant' | 'system';
+  content: string;
+  createdAt: Date;
+}
+
 export function createConversationsRepo(db: Db) {
   return {
     async findAll(userId: string): Promise<Conversation[]> {
@@ -87,6 +96,35 @@ export function createConversationsRepo(db: Db) {
         .limit(MAX_MESSAGES);
     },
 
+    /**
+     * Search messages by content across all conversations belonging to the user.
+     * Uses ILIKE for case-insensitive substring matching.
+     */
+    async searchMessages(
+      userId: string,
+      query: string,
+      limit: number,
+      offset: number,
+    ): Promise<MessageSearchResult[]> {
+      const rows = await db
+        .select({
+          messageId: messages.id,
+          conversationId: conversations.id,
+          conversationTitle: conversations.title,
+          role: messages.role,
+          content: messages.content,
+          createdAt: messages.createdAt,
+        })
+        .from(messages)
+        .innerJoin(conversations, eq(messages.conversationId, conversations.id))
+        .where(and(eq(conversations.userId, userId), ilike(messages.content, `%${query}%`)))
+        .orderBy(desc(messages.createdAt))
+        .limit(limit)
+        .offset(offset);
+
+      return rows;
+    },
+
     /**
      * Add a message to a conversation, scoped to the given user.
      * Verifies the parent conversation belongs to the user before inserting.

packages/brain/src/index.ts

@@ -25,6 +25,7 @@ export {
   type NewConversation,
   type Message,
   type NewMessage,
+  type MessageSearchResult,
 } from './conversations.js';
 export {
   createAgentsRepo,

packages/db/src/index.ts

@@ -15,4 +15,5 @@ export {
   lt,
   gte,
   lte,
+  ilike,
 } from 'drizzle-orm';