port mintlify to fumadocs

app/api/chat/route.ts

@@ -0,0 +1,80 @@
+import {
+  convertToModelMessages,
+  createUIMessageStreamResponse,
+  stepCountIs,
+  streamText,
+  toUIMessageStream,
+  type SystemModelMessage,
+} from 'ai';
+import type { ChatUIMessage } from '@/components/ai/search';
+import { AIConfigError, getModel } from '@/lib/ai/model';
+import { getSystemPrompt } from '@/lib/ai/prompt';
+import { checkRateLimit, clientKey } from '@/lib/ai/rate-limit';
+import { tools } from '@/lib/ai/tools';
+
+export const maxDuration = 120;
+
+const MAX_MESSAGES = 30;
+const MAX_MESSAGE_CHARS = 8_000;
+
+function json(status: number, message: string, headers?: HeadersInit) {
+  return Response.json({ error: message }, { status, headers });
+}
+
+export async function POST(req: Request) {
+  const limit = checkRateLimit(clientKey(req));
+  if (!limit.ok) {
+    return json(429, `Too many questions, try again in ${limit.retryAfter}s.`, {
+      'Retry-After': String(limit.retryAfter),
+    });
+  }
+
+  let config;
+  try {
+    config = getModel();
+  } catch (e) {
+    if (e instanceof AIConfigError) return json(503, e.message);
+    throw e;
+  }
+
+  const body = (await req.json().catch(() => null)) as { messages?: ChatUIMessage[] } | null;
+  const messages = (body?.messages ?? []).slice(-MAX_MESSAGES);
+  const tooLong = messages.some((m) =>
+    m.parts.some((p) => p.type === 'text' && p.text.length > MAX_MESSAGE_CHARS),
+  );
+  if (messages.length === 0 || tooLong) return json(400, 'Invalid or too long message.');
+
+  const instructions: SystemModelMessage = {
+    role: 'system',
+    content: getSystemPrompt(),
+    // the system prompt is large and identical across requests
+    providerOptions: { anthropic: { cacheControl: { type: 'ephemeral' } } },
+  };
+
+  const result = streamText({
+    model: config.model,
+    stopWhen: stepCountIs(8),
+    tools,
+    toolChoice: 'auto',
+    instructions,
+    messages: await convertToModelMessages<ChatUIMessage>(messages, {
+      convertDataPart(part) {
+        if (part.type === 'data-client')
+          return {
+            type: 'text',
+            text: `[Client Context: ${JSON.stringify(part.data)}]`,
+          };
+      },
+    }),
+    onError({ error }) {
+      console.error('[api/chat]', error);
+    },
+  });
+
+  return createUIMessageStreamResponse({
+    stream: toUIMessageStream({
+      stream: result.stream,
+      onError: () => 'The assistant hit an error. Please try again.',
+    }),
+  });
+}