const ALLOWED_CHAT_IMAGE_MIME = new Set(["image/jpeg", "image/png", "image/gif", "image/webp"]);
const MAX_CHAT_IMAGES = 8;
const MAX_CHAT_IMAGE_BYTES = 10 * 1024 * 1024;

export function normalizeChatImages(
	images: unknown,
): Array<{ type: "image"; data: string; mimeType: string }> | undefined {
	if (!Array.isArray(images) || images.length === 0) return undefined;
	const out: Array<{ type: "image"; data: string; mimeType: string }> = [];
	for (const raw of images.slice(0, MAX_CHAT_IMAGES)) {
		if (!raw || typeof raw !== "object") continue;
		const mimeType = String((raw as { mimeType?: string }).mimeType || "");
		const data = String((raw as { data?: string }).data || "");
		if ((raw as { type?: string }).type !== "image" || !ALLOWED_CHAT_IMAGE_MIME.has(mimeType) || !data) {
			throw new Error(`不支持的图片类型: ${mimeType || "unknown"}`);
		}
		const size = Buffer.from(data, "base64").length;
		if (size > MAX_CHAT_IMAGE_BYTES) {
			throw new Error(`图片过大（最大 ${Math.round(MAX_CHAT_IMAGE_BYTES / 1024 / 1024)}MB）`);
		}
		out.push({ type: "image", mimeType, data });
	}
	return out.length ? out : undefined;
}