backend/src/gallery/dto/gallery.dto.ts

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

function toStringArray(value: unknown): string[] | undefined {
  if (value == null || value === '') return undefined;
  if (Array.isArray(value)) {
    return value.map((item) => String(item)).filter(Boolean);
  }
  if (typeof value === 'string') {
    const trimmed = value.trim();
    if (!trimmed) return undefined;
    try {
      const parsed = JSON.parse(trimmed) as unknown;
      if (Array.isArray(parsed)) {
        return parsed.map((item) => String(item)).filter(Boolean);
      }
    } catch {
      // comma-separated fallback
    }
    return trimmed
      .split(',')
      .map((item) => item.trim())
      .filter(Boolean);
  }
  return undefined;
}

export class ListGalleryDto {
  @IsOptional()
  @Type(() => Number)
  @IsInt()
  @Min(1)
  page?: number;

  @IsOptional()
  @Type(() => Number)
  @IsInt()
  @Min(1)
  @Max(100)
  pageSize?: number;
}

export class AddGalleryDto {
  /** Attach existing business media (also accepted as multipart field). */
  @IsOptional()
  @Transform(({ value }) => toStringArray(value))
  @IsArray()
  @ArrayMaxSize(50)
  @IsString({ each: true })
  mediaIds?: string[];
}