export type PosterMaterial = {
  key: string;
  amount: number;
  name: string;
  imageUrl: string | null;
};

export function mergePosterMaterials(materials: PosterMaterial[]): PosterMaterial[] {
  const merged: PosterMaterial[] = [];
  const indexByImageUrl = new Map<string, number>();

  for (const material of materials) {
    if (!material.imageUrl) {
      merged.push(material);
      continue;
    }

    const existingIndex = indexByImageUrl.get(material.imageUrl);
    if (existingIndex === undefined) {
      indexByImageUrl.set(material.imageUrl, merged.length);
      merged.push(material);
      continue;
    }

    const existing = merged[existingIndex];
    merged[existingIndex] = {
      ...existing,
      amount: existing.amount + material.amount,
    };
  }

  return merged;
}