import {
  FindManyOptions,
  FindOptionsWhere,
  Repository,
  SelectQueryBuilder,
} from 'typeorm';
import { PaginationParams } from '../interface';
import { plainToInstance } from 'class-transformer';

export class PaginationResult<T> {
  current: number;

  pageSize: number;

  total: number;

  items: T[];
}

export async function paginate<T>(
  repository: Repository<T> | SelectQueryBuilder<T>,
  options: {
    pagination: PaginationParams;
    where?: FindOptionsWhere<T> | FindOptionsWhere<T>[];
    relations?: string[];
    order?: Record<string, 'ASC' | 'DESC'>;
    transformerClass?: new () => T; // 可选：用于指定需要转换的类
  }
): Promise<PaginationResult<T>> {
  const {
    pagination: { current, pageSize },
    relations = [],
    where = {},
    order = {},
    transformerClass,
  } = options;

  if (repository instanceof SelectQueryBuilder) {
    let queryBuilder = repository;
    const total = await queryBuilder.getCount();
    queryBuilder = queryBuilder.skip((current - 1) * pageSize).take(pageSize);

    const items = await queryBuilder.getRawMany();
    const transformedItems = transformerClass
      ? plainToInstance(transformerClass, items)
      : items;
    return {
      items: transformedItems,
      total,
      current,
      pageSize,
    };
  }

  const items = await repository.find({
    where,
    skip: (current - 1) * pageSize,
    take: pageSize,
    relations,
    order,
  } as FindManyOptions<T>);
  const total = await repository.count({
    where,
    take: pageSize,
    relations,
    order,
  } as FindManyOptions<T>);
  const transformedItems = transformerClass
    ? plainToInstance(transformerClass, items)
    : items;
  return {
    items: transformedItems,
    total,
    current,
    pageSize,
  };
}