(function (root, factory) {
  const exports = factory();
  if (typeof module === 'object' && module.exports) {
    module.exports = exports.createFollowing;
    module.exports.attachFollowing = exports.attachFollowing;
  } else {
    root.createFollowing = exports.createFollowing;
    root.attachFollowing = exports.attachFollowing;
  }
})(typeof self !== 'undefined' ? self : this, function () {
  function createFollowing(options) {
    let generation = 0;
    let snapshot = {revision:0, items:[]};

    function publish(status, error) {
      const state = {status, revision:snapshot.revision, items:[...snapshot.items]};
      if (error) state.error = error;
      options.render?.(state);
      if (status === 'ready') options.onCount?.(snapshot.items.length);
      return state;
    }

    async function load() {
      const requestGeneration = ++generation;
      publish('loading');
      try {
        const result = await options.fetchJson('api/v1/following', {headers:{Accept:'application/json'}});
        if (requestGeneration !== generation) return snapshot;
        snapshot = {
          revision:Number(result?.revision) || 0,
          items:Array.isArray(result?.items) ? result.items.slice(0, 50) : [],
        };
        publish('ready');
        return snapshot;
      } catch (error) {
        if (requestGeneration === generation) publish('error', error);
        throw error;
      }
    }

    function open(index) {
      const item = snapshot.items[Number(index)];
      if (!item) return false;
      Promise.resolve(options.onOpen?.({...item, kind:'issue'})).catch(() => {});
      return true;
    }

    return {load, open, count:() => snapshot.items.length};
  }

  function attachFollowing(onOpen) {
    const document = globalThis.document;
    const query = selector => document.querySelector(selector);
    const escapeHtml = value => String(value ?? '').replace(/[&<>"']/g, character =>
      ({'&':'&amp;','<':'&lt;','>':'&gt;','"':'&quot;',"'":'&#39;'})[character]);
    const formatTime = value => new Date(value).toLocaleString();
    const fetchJson = async (url, options) => {
      const response = await fetch(url, options);
      const payload = await response.json().catch(() => ({}));
      if (!response.ok) throw new Error(payload.detail || payload.error || 'Following is temporarily unavailable.');
      return payload;
    };
    let feature;
    function render(state) {
      const list = query('#following-list');
      const status = query('#following-status');
      query('#retry-following').hidden = state.status !== 'error';
      if (state.status === 'loading') return void (status.textContent = 'Loading watched issues…');
      if (state.status === 'error') return void (status.textContent = state.error?.message || 'Following is temporarily unavailable.');
      status.textContent = state.items.length
        ? state.items.length + (state.items.length === 1 ? ' watched issue.' : ' watched issues.')
        : 'No watched issues yet. Watch one from Search to keep it here.';
      list.innerHTML = state.items.map((item, index) =>
        '<button class="following-card" type="button" data-following-index="' + index + '"><span><strong>' +
        escapeHtml(item.title) + '</strong><small>' + escapeHtml(item.repository + ' #' + item.number +
        ' · ' + item.state + ' · ' + formatTime(item.updated_at)) +
        '</small></span><span aria-hidden="true">›</span></button>').join('');
      list.querySelectorAll('[data-following-index]').forEach(button => button.addEventListener('click', () => {
        query('#following-sheet').close();
        feature.open(Number(button.dataset.followingIndex));
      }));
    }
    feature = createFollowing({
      fetchJson, render,
      onCount:count => {
        const value = query('[data-mobile-queue-count="following"]');
        value.textContent = count;
        value.closest('button').setAttribute('aria-label', 'Following, ' + count +
          (count === 1 ? ' watched issue' : ' watched issues'));
      },
      onOpen,
    });
    query('#close-following').addEventListener('click', () => query('#following-sheet').close());
    query('#retry-following').addEventListener('click', () => feature.load().catch(() => {}));
    feature.load().catch(() => {});
    return {
      load:feature.load,
      open() {
        const sheet = query('#following-sheet');
        if (!sheet.open) sheet.showModal();
        feature.load().catch(() => {});
        return 'opened-following';
      },
    };
  }

  return {createFollowing, attachFollowing};
});