Fix live multi-turn: pass the resolved drug, stop did-you-mean garbage

packages/api-client/src/sendChatMessage.ts

@@ -1,9 +1,43 @@
 import type { SendMessageResponse } from "@duoc-thu/shared-types";
 import { buildMockResponse } from "./mockFixtures";
 
-const MOCK_LATENCY_MS = 400;
+/**
+ * Sends a question to the real RAG backend through the app's own route
+ * handler, which holds the service URL and maps the response.
+ *
+ * The mock is retained but is now opt-in via `NEXT_PUBLIC_USE_MOCK_CHAT`, and
+ * every mocked answer is labelled as such in its own text. Silently falling
+ * back to a plausible-looking fake answer is the exact failure this project
+ * cannot afford: a fabricated dose that looks like a real one.
+ */
+const USE_MOCK = process.env.NEXT_PUBLIC_USE_MOCK_CHAT === "true";
 
-export async function sendChatMessage(content: string): Promise<SendMessageResponse> {
-  await new Promise((resolve) => setTimeout(resolve, MOCK_LATENCY_MS));
-  return buildMockResponse(content);
+export class ChatUnavailableError extends Error {
+  constructor(readonly status: number) {
+    super(`Chat backend unavailable (${status})`);
+    this.name = "ChatUnavailableError";
+  }
+}
+
+export async function sendChatMessage(
+  content: string,
+  conversationId?: string
+): Promise<SendMessageResponse> {
+  if (USE_MOCK) {
+    await new Promise((resolve) => setTimeout(resolve, 400));
+    return buildMockResponse(content);
+  }
+
+  const response = await fetch("/api/chat", {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify({ content, conversationId }),
+  });
+
+  if (!response.ok) {
+    // Surfaced to the user as an error state, never as an answer.
+    throw new ChatUnavailableError(response.status);
+  }
+
+  return (await response.json()) as SendMessageResponse;
 }