function createIssueSheet({ fetchJson, storage }) {
  let commentRequest = null;
  let closeRequest = null;
  let labelRequest = null;
  const issuePath = item => 'api/v1/repos/' + item.repository.split('/').map(encodeURIComponent).join('/') +
    '/issues/' + encodeURIComponent(item.number);
  const draftKey = item => 'stackchain.issue-comment.v1:' + item.repository + '#' + item.number;
  const labelDraftKey = item => 'stackchain.issue-labels.v1:' + item.repository + '#' + item.number;

  return {
    load(item) {
      return fetchJson(issuePath(item) + '/detail', {
        headers: { Accept: 'application/json' },
      });
    },
    loadLabels(item) {
      return fetchJson(issuePath(item) + '/labels', {
        headers: { Accept: 'application/json' },
      });
    },
    loadDraft(item) {
      try { return storage?.getItem(draftKey(item)) || ''; }
      catch (_error) { return ''; }
    },
    saveDraft(item, body) {
      try { storage?.setItem(draftKey(item), body); }
      catch (_error) { /* The textarea remains the fallback. */ }
    },
    loadLabelDraft(item) {
      try {
        const value = JSON.parse(storage?.getItem(labelDraftKey(item)) || '[]');
        return Array.isArray(value) ? value.filter(Number.isInteger) : [];
      } catch (_error) { return []; }
    },
    updateLabels(item, labelIds) {
      if (labelRequest) return labelRequest;
      try { storage?.setItem(labelDraftKey(item), JSON.stringify(labelIds)); }
      catch (_error) { /* The checked controls remain the fallback. */ }
      labelRequest = fetchJson(issuePath(item) + '/labels', {
        method: 'PATCH',
        headers: { Accept: 'application/json', 'Content-Type': 'application/json' },
        body: JSON.stringify({ label_ids: labelIds }),
      }).then(result => {
        if (result?.number !== item.number || !Array.isArray(result.labels)) {
          throw new Error('Issue labels were not confirmed.');
        }
        try { storage?.removeItem(labelDraftKey(item)); }
        catch (_error) { /* The upstream label set is authoritative. */ }
        return result;
      }).finally(() => { labelRequest = null; });
      return labelRequest;
    },
    close(item) {
      if (closeRequest) return closeRequest;
      closeRequest = fetchJson(issuePath(item) + '/close', {
        method: 'PATCH',
        headers: { Accept: 'application/json' },
      }).then(result => {
        if (result?.state !== 'closed') throw new Error('Issue closure was not confirmed.');
        return result;
      }).finally(() => { closeRequest = null; });
      return closeRequest;
    },
    comment(item, body) {
      if (commentRequest) return commentRequest;
      this.saveDraft(item, body);
      commentRequest = fetchJson(issuePath(item) + '/comments', {
        method: 'POST',
        headers: { Accept: 'application/json', 'Content-Type': 'application/json' },
        body: JSON.stringify({ body }),
      }).then(result => {
        try { storage?.removeItem(draftKey(item)); }
        catch (_error) { /* The upstream comment is authoritative. */ }
        return result;
      }).finally(() => { commentRequest = null; });
      return commentRequest;
    },
  };
}

if (typeof module !== 'undefined' && module.exports) module.exports = createIssueSheet;