const dayjs = require('dayjs');

exports.generateRandomString = (length) => {
  const characters = "0123456789abcdefghijklmnopqrstuvwxyz";
  let result = "";
  const charactersLength = characters.length;

  for (let i = 0; i < length; i++) {
    const randomIndex = Math.floor(Math.random() * charactersLength);
    result += characters[randomIndex];
  }
  return `${result}${Date.now()}`;
};

/**
 * 生成唯一字符串
 * @param {*} prefix 唯一字符串前缀
 * @param {*} len 补充字符串长度
 * @description 总长度 = prefix.length + 固定15 (当前时间的长度 YYMMDDHHmmssSSS格式) + 补充字符串的长度
 */
exports.generateUniqueStr = (prefix = '', len = 6) => {
  const dateStamp = dayjs().format('YYMMDDHHmmssSSS');
  const groups = Math.ceil(len / 4); // 4个字符串一组
  const suffix = new Array(groups).fill(1).map((_, idx) => {
    const exponent = Math.min(4, len - idx * 4);
    const str = Math.floor(Math.random() * (10 ** exponent)).toString().padStart(exponent, '0');
    return str;
  }).join('');
  return `${prefix}${dateStamp}${suffix}`;
}

exports.getAttachments = (fileList, sopTaskId, executeUserId) => {
  if (!Array.isArray(fileList)) return [];
  return fileList.map((item) => {
    let { type, mediaId, file, URL } = item;
    let { subtitle, name, url, type: fileType } = file;
    let attachment = {};
    if (type === "image") {
      attachment = {
        msgtype: type,
        title: name,
        image: {
          media_id: mediaId,
        },
      };
    } else if (type === "video") {
      attachment = {
        msgtype: type,
        title: name,
        video: {
          media_id: mediaId,
        },
      };
    } else if (type === "link") {
      attachment = {
        msgtype: type,
        title: name,
        linkType: fileType || "",
        link: {
          title: name,
          picurl: URL,
          desc: subtitle,
          url:
            fileType === "questionnaire"
              ? `${url}&id=${sopTaskId}&source=sop&userId=${executeUserId}`
              : url,
        },
      };
    }
    return attachment;
  });
};

/**
 * 批量执行任务，控制最大并发数
 * @param {Array} items - 待处理的任务参数列表
 * @param {Function} taskFn - 单个任务的处理函数，需返回 Promise
 * @param {number} maxConcurrency - 最大并发数
 * @returns {Promise<Array>} - 返回所有任务的结果
 */
exports.executeWithConcurrency = async (items, taskFn, maxConcurrency) => {
  let index = 0;
  const results = [];

  while (index < items.length) {
    // 获取当前批次
    const batch = items.slice(index, index + maxConcurrency);

    // 映射当前批次的任务并执行
    const promises = batch.map((item) => taskFn(item));

    // 等待当前批次的任务完成
    const batchResults = await Promise.all(promises);

    // 收集结果
    results.push(...batchResults);

    // 更新索引
    index += maxConcurrency;
  }

  return results;
};