import { NestFactory } from '@nestjs/core';
import { ExpressAdapter } from '@nestjs/platform-express';
import { AppModule } from '../dist/app.module';
import { ValidationPipe } from '@nestjs/common';
import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger';
import * as express from 'express';

// 缓存 app 实例，避免每次冷启动都重新创建
let cachedApp: any;

async function bootstrap() {
  if (!cachedApp) {
    const expressApp = express();
    const app = await NestFactory.create(
      AppModule,
      new ExpressAdapter(expressApp),
    );

    // 配置 CORS
    app.enableCors({
      origin: [
        'https://tradingadvfrontend.vercel.app',
        'http://localhost:8000',
        'http://localhost:3030',
      ],
      credentials: true,
      methods: ['GET', 'POST', 'PUT', 'DELETE', 'PATCH', 'OPTIONS'],
      allowedHeaders: [
        'Content-Type',
        'Authorization',
        'Accept',
        'Origin',
        'Referer',
        'User-Agent',
      ],
    });

    // 全局验证管道
    app.useGlobalPipes(
      new ValidationPipe({
        whitelist: true,
        forbidNonWhitelisted: true,
        transform: true,
      }),
    );

    // Swagger 文档
    const config = new DocumentBuilder()
      .setTitle('API 文档')
      .setVersion('1.0')
      .addBearerAuth()
      .build();
    const document = SwaggerModule.createDocument(app, config);
    SwaggerModule.setup('api', app, document);

    await app.init();
    cachedApp = expressApp;
  }
  return cachedApp;
}

// Vercel Serverless handler
export default async function handler(req: any, res: any) {
  const app = await bootstrap();
  app(req, res);
}