export interface AttachmentFile {
  name: string;
  url: string;
}

const FILE_EXT_PATTERN =
  /\.(pdf|docx?|xlsx?|pptx?|csv|txt|zip|rar|7z|jpe?g|png|gif|webp|bmp|svg|mp4|mp3|wav)$/i;

/**
 * 从文件地址中取出展示用的文件名
 */
export function getAttachmentName(url?: string) {
  if (!url) {
    return '未命名文件';
  }
  const cleanUrl = url.split('?')[0];
  const name = cleanUrl.split('/').pop() || cleanUrl;
  try {
    return decodeURIComponent(name);
  } catch (e) {
    return name;
  }
}

/**
 * 判断字符串是否像文件地址（http(s)、协议相对地址、带扩展名的相对路径）
 */
export function isFileUrl(value?: string) {
  const text = value?.trim();
  if (!text) {
    return false;
  }
  if (/^(https?:)?\/\//i.test(text)) {
    return true;
  }
  return FILE_EXT_PATTERN.test(text) && !/\s/.test(text);
}

export function isImageFile(url?: string) {
  const text = (url || '').split('?')[0];
  return /\.(jpe?g|png|gif|webp|bmp|svg)$/i.test(text);
}

const normalizeEntry = (item: unknown): AttachmentFile | null => {
  if (typeof item === 'string') {
    return isFileUrl(item)
      ? { name: getAttachmentName(item), url: item.trim() }
      : null;
  }
  if (item && typeof item === 'object') {
    const record = item as Record<string, unknown>;
    const rawUrl = [
      record.url,
      record.fileUrl,
      record.downloadUrl,
      record.path
    ].find((value) => typeof value === 'string' && isFileUrl(value as string));
    if (typeof rawUrl !== 'string') {
      return null;
    }
    const rawName = [record.name, record.fileName, record.originalName].find(
      (value) => typeof value === 'string' && (value as string).trim()
    );
    return {
      name: (rawName as string | undefined) || getAttachmentName(rawUrl),
      url: rawUrl.trim()
    };
  }
  return null;
};

/**
 * 把后端存储的附件字段解析成文件列表。
 * 兼容：单个地址、JSON 数组字符串、对象数组（name/url、fileName/fileUrl 等）
 */
export function parseAttachments(value: unknown): AttachmentFile[] {
  if (value === null || value === undefined || value === '') {
    return [];
  }
  if (typeof value === 'string') {
    const text = value.trim();
    if (!text) {
      return [];
    }
    if (text.startsWith('[') || text.startsWith('{')) {
      try {
        return parseAttachments(JSON.parse(text));
      } catch (e) {
        // 解析失败时按普通地址处理
      }
    }
    const single = normalizeEntry(text);
    return single ? [single] : [];
  }
  if (Array.isArray(value)) {
    return value
      .map((item) => normalizeEntry(item))
      .filter((item): item is AttachmentFile => !!item);
  }
  const single = normalizeEntry(value);
  return single ? [single] : [];
}

/**
 * 把附件字段解析结果转换成图片地址列表
 */
export function parseAttachmentImages(value: unknown) {
  const urls: string[] = [];
  parseAttachments(value).forEach((item) => {
    if (isImageFile(item.url)) {
      urls.push(item.url);
    }
  });
  if (!urls.length && typeof value === 'string' && isImageFile(value)) {
    urls.push(value);
  }
  return urls;
}