feat: implement chat API with agent streaming capabilities

- Added new API route for chat functionality in r.ts.
- Integrated agent streaming response using createAgentStreamResponse.
- Implemented error handling for invalid agent IDs and missing messages.
- Returned available agents and their count in the GET request.

Author: ssdeanx

app/api/chat/r.ts

@@ -0,0 +1,64 @@
+import { mastra } from "@/src/mastra";
+import { createAgentStreamResponse } from "@/lib/client-stream-to-ai-sdk";
+import type { UIMessage } from "ai";
+
+export const maxDuration = 60;
+
+interface ChatRequestBody {
+  messages: UIMessage[];
+  agentId?: string;
+  threadId?: string;
+  resourceId?: string;
+  memory?: {
+    thread?: string | { id: string; resourceId?: string };
+    resource?: string;
+    options?: {
+      lastMessages?: number;
+      semanticRecall?: boolean;
+      workingMemory?: { enabled?: boolean };
+    };
+  };
+  maxSteps?: number;
+}
+
+export async function POST(req: Request) {
+  const body: ChatRequestBody = await req.json();
+  
+  // Get available agents dynamically from mastra
+  const agentsMap = await mastra.getAgents();
+  const availableAgents = Object.keys(agentsMap);
+  
+  // Use first available agent if none specified
+  const agentId = body.agentId || availableAgents[0];
+  
+  if (!agentId || !availableAgents.includes(agentId)) {
+    return Response.json(
+      { error: `Invalid or missing agentId. Available: ${availableAgents.join(", ")}` },
+      { status: 400 }
+    );
+  }
+
+  if (!body.messages?.length) {
+    return Response.json({ error: "messages required" }, { status: 400 });
+  }
+  
+  try {
+    return await createAgentStreamResponse(mastra as Parameters<typeof createAgentStreamResponse>[0], agentId, body.messages, {
+      threadId: body.threadId,
+      resourceId: body.resourceId,
+      memory: body.memory,
+      maxSteps: body.maxSteps ?? 50,
+    });
+  } catch (error) {
+    return Response.json(
+      { error: error instanceof Error ? error.message : "Stream failed" },
+      { status: 500 }
+    );
+  }
+}
+
+export async function GET() {
+  const agentsMap = await mastra.getAgents();
+  const availableAgents = Object.keys(agentsMap);
+  return Response.json({ agents: availableAgents, count: availableAgents.length });
+}

lib/client-stream-to-ai-sdk.ts

@@ -50,7 +50,7 @@ async function* asyncIterableFromReadableStream<T>(
 /**
  * Creates a streaming Response for Next.js API routes using server-side Mastra agent.
  * 
- * IMPORTANT: This should be used in API routes with the SERVER-SIDE mastra instance,
+ * IMPORTANT: This should be used in API 5stra instance,
  * not the client SDK. The client SDK (MastraClient) is for frontend use only.
  * 
  * @example