import { NestFactory } from '@nestjs/core';
import { ExpressAdapter } from '@nestjs/platform-express';
import { ValidationPipe } from '@nestjs/common';
import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger';
import express from 'express';
import bodyParser from 'body-parser';
import * as path from 'path';

// 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();

    // 动态解析 dist 目录路径
    // 在 Vercel 环境中，__dirname 是 /var/task/api
    // dist 目录在 /var/task/dist
    const distPath = path.resolve(__dirname, '..', 'dist', 'app.module');
    console.log('Loading AppModule from:', distPath);

    const { AppModule } = require(distPath);

    const app = await NestFactory.create(
      AppModule,
      new ExpressAdapter(expressApp),
      { logger: ['error', 'warn', 'log'] },
    );

    // 配置 CORS
    app.enableCors({
      origin: true, // 允许所有来源
      credentials: true,
      methods: ['GET', 'POST', 'PUT', 'DELETE', 'PATCH', 'OPTIONS'],
      allowedHeaders: [
        'Content-Type',
        'Authorization',
        'Accept',
        'Origin',
        'Referer',
        'User-Agent',
      ],
    });

    // 尝试加载全局过滤器和拦截器
    try {
      const httpExceptionFilterPath = path.resolve(
        __dirname,
        '..',
        'dist',
        'common',
        'filters',
        'http-exception.filter',
      );
      const transformInterceptorPath = path.resolve(
        __dirname,
        '..',
        'dist',
        'common',
        'interceptors',
        'transform.interceptor',
      );

      const { HttpExceptionFilter } = require(httpExceptionFilterPath);
      const { TransformInterceptor } = require(transformInterceptorPath);
      app.useGlobalFilters(new HttpExceptionFilter());
      app.useGlobalInterceptors(new TransformInterceptor());
    } catch (error) {
      console.log('Global filters/interceptors not loaded:', error.message);
    }

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

    // Body parser 配置
    app.use(bodyParser.json({ limit: '50mb' }));
    app.use(bodyParser.urlencoded({ limit: '50mb', extended: true }));

    // Swagger 文档
    const config = new DocumentBuilder()
      .setTitle('API 文档')
      .setDescription('这是我的应用程序的 API 文档')
      .setVersion('1.0')
      .addBearerAuth()
      .build();
    const document = SwaggerModule.createDocument(app, config);
    SwaggerModule.setup('docs', app, document);

    await app.init();
    cachedApp = expressApp;

    console.log('NestJS app initialized successfully');
  }
  return cachedApp;
}

// Vercel Serverless handler
export default async function handler(req: any, res: any) {
  try {
    console.log(`Request: ${req.method} ${req.url}`);
    const app = await bootstrap();
    app(req, res);
  } catch (error) {
    console.error('Handler error:', error);
    res.status(500).json({
      error: 'Internal Server Error',
      message: error.message,
      stack: process.env.NODE_ENV === 'development' ? error.stack : undefined,
    });
  }
}