import { BadRequestException } from '@nestjs/common';

/**
 * A wagon carries ONE 40ft OR TWO 20ft empties — never a mix, never three.
 * Throws on the first wagon that breaks the rule.
 */
export function assertWagonLoad(sizesByWagon: Map<number, string[]>): void {
  for (const [wagon, sizes] of sizesByWagon) {
    const has40 = sizes.some((size) => size === '40');
    if ((has40 && sizes.length > 1) || sizes.length > 2) {
      throw new BadRequestException(
        `Wagon ${wagon} takes one 40ft or two 20ft containers — got ${sizes.join('ft + ')}ft`,
      );
    }
  }
}