import { Type } from 'class-transformer';
import { IsInt, IsOptional, Max, Min } from 'class-validator';

/** 契约 data-models.md §1：列表接口统一分页参数 */
export class PageQueryDto {
  @IsOptional()
  @Type(() => Number)
  @IsInt()
  @Min(1)
  page: number = 1;

  @IsOptional()
  @Type(() => Number)
  @IsInt()
  @Min(1)
  @Max(200)
  pageSize: number = 20;

  get skip(): number {
    return (this.page - 1) * this.pageSize;
  }
}

export interface Paged<T> {
  items: T[];
  total: number;
  page: number;
  pageSize: number;
}

export function toPaged<T>(items: T[], total: number, query: { page: number; pageSize: number }): Paged<T> {
  return { items, total, page: query.page, pageSize: query.pageSize };
}

/** 规范化分页参数（用于非 DTO 校验路径，如内部调用） */
export function normalizePaging(page?: number, pageSize?: number, maxPageSize = 200): { page: number; pageSize: number; skip: number } {
  const p = Number.isFinite(page) && (page as number) >= 1 ? Math.floor(page as number) : 1;
  const rawSize = Number.isFinite(pageSize) ? Math.floor(pageSize as number) : 20;
  const size = Math.min(Math.max(rawSize, 1), maxPageSize);
  return { page: p, pageSize: size, skip: (p - 1) * size };
}