/**
 * 选集智能折叠分页 —— 纯函数，无 DOM 依赖，便于单元测试。
 * 返回 [{n:number} | {dot:true}] 序列；{dot:true} 表示可点击的省略号。
 *
 * @param {number} total    总集数
 * @param {number} current  当前集（1-based）
 * @param {{threshold?:number, edge?:number, around?:number}} opts
 */
(function () {
  'use strict';

  function paginate(total, current, opts) {
    opts = opts || {};
    const threshold = opts.threshold > 0 ? opts.threshold : 12;   // 超过则折叠
    const edge = opts.edge > 0 ? opts.edge : 3;                   // 首尾各展示数
    const around = opts.around >= 0 ? opts.around : 2;            // 当前前后各展示数

    total = Math.max(0, Math.floor(total));
    current = Math.min(total, Math.max(1, Math.floor(current)));
    const out = [];
    if (total === 0) return out;
    if (total <= threshold) {
      for (let i = 1; i <= total; i++) out.push({ n: i });
      return out;
    }

    const set = new Set();
    for (let i = 1; i <= edge && i <= total; i++) set.add(i);
    for (let i = total - edge + 1; i <= total; i++) if (i >= 1) set.add(i);
    for (let i = current - around; i <= current + around; i++) if (i >= 1 && i <= total) set.add(i);

    const sorted = Array.from(set).sort((a, b) => a - b);
    let prev = 0;
    for (const n of sorted) {
      const d = n - prev;
      if (d > 2) out.push({ dot: true });
      else if (d === 2) out.push({ n: prev + 1 }); // 只差一个隐藏集，直接展示
      out.push({ n });
      prev = n;
    }
    return out;
  }

  window.EpisodePaginator = { paginate: paginate };
})();