import {
  PipeTransform,
  Injectable,
  ArgumentMetadata,
  BadRequestException,
} from '@nestjs/common';
import { validate } from 'class-validator';
import { plainToInstance } from 'class-transformer';
import { ErrorCode } from '../interfaces/response.interface';

/**
 * 全局验证管道
 * 自动验证 DTO 并返回统一格式的错误
 */
@Injectable()
export class ValidationPipe implements PipeTransform<any> {
  async transform(value: any, { metatype }: ArgumentMetadata) {
    if (!metatype || !this.toValidate(metatype)) {
      return value;
    }

    const object = plainToInstance(metatype, value);
    const errors = await validate(object);

    if (errors.length > 0) {
      const messages = errors
        .map((error) => Object.values(error.constraints || {}).join(', '))
        .join('; ');

      throw new BadRequestException({
        code: ErrorCode.PARAM_ERROR,
        message: messages,
      });
    }

    return object;
  }

  private toValidate(metatype: Function): boolean {
    const types: Function[] = [String, Boolean, Number, Array, Object];
    return !types.includes(metatype);
  }
}