class Container {
  constructor() {
    this.registry = new Map();
    this.instances = new Map(); // 缓存单例
  }

  register(name, ctor, lifecycle = 'singleton') {
    this.registry.set(name, { ctor, lifecycle });
    return this;
  }

  resolve(name) {
    if (!this.registry.has(name)) {
      throw new Error(`Service not registered: ${name}`);
    }

    const { ctor, lifecycle } = this.registry.get(name);

    if (lifecycle === 'singleton' && this.instances.has(name)) {
      return this.instances.get(name);
    }

    const instance = this._instantiate(ctor);
    
    if (lifecycle === 'singleton') {
      this.instances.set(name, instance);
    }

    return instance;
  }

  _instantiate(ctor) {
    const paramRegex = /constructor\s*\(\s*([^)]*)\)/;
    const argsStr = ctor.toString().match(paramRegex)?.[1] || '';
    const deps = argsStr.split(',').map(arg => arg.trim()).filter(Boolean);

    const dependencies = deps.map(dep => {
      if (!this.registry.has(dep)) {
        throw new Error(`Dependency not registered: ${dep}`);
      }
      return this.resolve(dep);
    });

    return Reflect.construct(ctor, dependencies);
  }
}

class Logger {
  log(msg) {
    console.log('[LOG]', msg);
  }
}

class UserService {
  constructor(Logger) {
    this.logger = Logger;
  }

  getUser(id) {
    this.logger.log(`Fetching user ${id}`);
    return { id, name: 'John Doe' };
  }
}

// 使用容器
const container = new Container();
container.register('Logger', Logger);
container.register('UserService', UserService);

const userService = container.resolve('UserService');
userService.getUser(1); // [LOG] Fetching user 1