FEAT: Chat API 구현

Author: taein8935

app/api/chat/route.ts

@@ -0,0 +1,87 @@
+import { Message as VercelChatMessage } from 'ai';
+import { RunnableSequence } from '@langchain/core/runnables';
+import { PromptTemplate } from '@langchain/core/prompts';
+import { ChatOpenAI } from '@langchain/openai';
+
+import { HttpResponseOutputParser } from 'langchain/output_parsers';
+import { JSONLoader } from 'langchain/document_loaders/fs/json';
+import { formatDocumentsAsString } from 'langchain/util/document';
+
+const loader = new JSONLoader('data/states.json', [
+  '/state',
+  '/code',
+  '/nickname',
+  '/website',
+  '/admission_date',
+  '/admission_number',
+  '/capital_city',
+  '/capital_url',
+  '/population',
+  '/population_rank',
+  '/constitution_url',
+  '/twitter_url',
+]);
+const formatMessage = (message: VercelChatMessage) => {
+  return `${message.role}: ${message.content}`;
+};
+
+const TEMPLATE = `
+Answer the user's questions based only on the following context. 
+If the answer is not in the context, reply politely that you do not have that information available.:
+==============================
+Context: {context}
+==============================
+Current conversation: {chat_history}
+
+user: {question}
+assistant:`;
+
+export async function POST(req: Request) {
+  try {
+    const { messages } = await req.json();
+
+    const formattedPreviousMessages = messages.slice(0, -1).map(formatMessage);
+
+    const currentMessageContent = messages[messages.length - 1].content;
+
+    const docs = await loader.load();
+
+    const prompt = PromptTemplate.fromTemplate(TEMPLATE);
+
+    const model = new ChatOpenAI({
+      apiKey: process.env.OPENAI_API_KEY!,
+      model: 'gpt-3.5-turbo',
+      temperature: 0,
+      streaming: true,
+    });
+
+    const parser = new HttpResponseOutputParser();
+
+    const chain = RunnableSequence.from([
+      {
+        question: (input) => input.question,
+        chat_history: (input) => input.chat_history,
+        context: () => formatDocumentsAsString(docs),
+      },
+      prompt,
+      model,
+      parser,
+    ]);
+
+    const stream = await chain.stream({
+      chat_history: formattedPreviousMessages.join('\n'),
+      question: currentMessageContent,
+    });
+
+    return new Response(stream, {
+      status: 200,
+      headers: { 'Content-Type': 'text/plain; charset=utf-8' },
+    });
+  } catch (error) {
+    console.error('라우팅 오류:', error);
+    return new Response(JSON.stringify({ error: '처리 실패' }), {
+      status: 500,
+      headers: { 'Content-Type': 'application/json' },
+    });
+  }
+}