💬 실시간 채팅 앱

// sendMessage Lambda — 메시지 브로드캐스트 함수 (Node.js 20.x 런타임)
import { DynamoDBClient } from '@aws-sdk/client-dynamodb';
import {
  ScanCommand,
  DeleteCommand,
  DynamoDBDocumentClient,
} from '@aws-sdk/lib-dynamodb';
import {
  ApiGatewayManagementApiClient,
  PostToConnectionCommand,
} from '@aws-sdk/client-apigatewaymanagementapi';
 
const ddb = DynamoDBDocumentClient.from(new DynamoDBClient({}));
const TABLE = process.env.CONNECTIONS_TABLE || 'chat-connections';
 
export const handler = async (event) => {
  const { connectionId, domainName, stage } = event.requestContext;
  const endpoint = `https://${domainName}/${stage}`;
  const apigw = new ApiGatewayManagementApiClient({ endpoint });
 
  const { message } = JSON.parse(event.body);
  const payload = JSON.stringify({
    action: 'message',
    sender: connectionId.slice(-6), // 발신자 식별용 짧은 ID
    message,
    timestamp: new Date().toISOString(),
  });
 
  // 모든 활성 연결 조회
  const { Items } = await ddb.send(new ScanCommand({ TableName: TABLE }));
 
  // 각 연결에 메시지 브로드캐스트
  const broadcasts = Items.map(async ({ connectionId: id }) => {
    try {
      await apigw.send(
        new PostToConnectionCommand({
          ConnectionId: id,
          Data: payload,
        })
      );
    } catch (err) {
      if (err.statusCode === 410) {
        // 410 Gone — 이미 끊어진 연결은 DynamoDB에서 정리
        await ddb.send(
          new DeleteCommand({
            TableName: TABLE,
            Key: { connectionId: id },
          })
        );
      }
    }
  });
 
  await Promise.all(broadcasts);
  return { statusCode: 200 };
};