function createReviewController({ fetchJson }) {
  function endpoint(item) {
    const [owner, repo] = String(item.repository || '').split('/');
    if (!owner || !repo || !Number.isInteger(Number(item.number))) {
      throw new Error('This review link is invalid.');
    }
    return 'api/v1/repos/' + encodeURIComponent(owner) + '/' + encodeURIComponent(repo) +
      '/pulls/' + Number(item.number) + '/review';
  }

  async function load(item) {
    return fetchJson(endpoint(item), { headers: { Accept: 'application/json' } });
  }

  return { load };
}

function diffLineClass(line) {
  if (line.startsWith('@@')) return 'hunk';
  if (line.startsWith('+')) return 'added';
  if (line.startsWith('-')) return 'removed';
  return 'context';
}

function renderDiffFile(file, index, escapeHtml) {
  const panelId = 'review-diff-' + index;
  let preview;
  if (file.diff_available) {
    const lines = (file.diff_lines || []).map(line =>
      '<span class="review-diff-line ' + diffLineClass(String(line)) + '">' +
      escapeHtml(String(line)) + '</span>'
    ).join('');
    preview = '<pre class="review-diff" id="' + panelId + '" hidden>' + lines +
      (file.diff_truncated ? '<span class="review-diff-note">Preview truncated · open in Gitea for the full diff.</span>' : '') +
      '</pre>';
  } else {
    const message = file.diff_binary ? 'Binary file · preview unavailable.' : 'Diff preview unavailable.';
    preview = '<div class="review-diff-empty" id="' + panelId + '" hidden>' + message +
      (file.diff_truncated ? ' The response was truncated.' : '') + '</div>';
  }
  const filename = escapeHtml(file.filename || 'Unknown file');
  return '<div class="review-file" data-review-filename="' + filename + '"><button class="review-file-toggle" aria-expanded="false" aria-controls="' + panelId + '">' +
    '<strong>' + filename + '</strong><span class="small">' +
    escapeHtml(file.status || 'changed') + ' · +' + Number(file.additions || 0) + ' / −' +
    Number(file.deletions || 0) + '</span></button>' + preview +
    '<button class="review-mark" data-review-filename="' + filename + '" aria-pressed="false">Mark reviewed</button></div>';
}

function toggleDiff(button, panel) {
  const expanded = button.getAttribute('aria-expanded') === 'true';
  button.setAttribute('aria-expanded', String(!expanded));
  panel.hidden = expanded;
}

function createProgress({ storage, repository, number, headSha, files }) {
  const filenames = (files || []).map(file => file && file.filename).filter(Boolean);
  const key = 'stackchain.review-progress.v1:' + repository + '#' + number + '@' + headSha;
  const headKey = 'stackchain.review-progress.v1:' + repository + '#' + number + ':head';
  let reviewed = [];
  let newHead = false;
  try {
    const previousHead = storage.getItem(headKey);
    newHead = Boolean(previousHead && previousHead !== headSha);
    storage.setItem(headKey, headSha);
    const saved = JSON.parse(storage.getItem(key) || '[]');
    if (Array.isArray(saved)) reviewed = filenames.filter(filename => saved.includes(filename));
  } catch (error) {
    reviewed = [];
  }

  function snapshot() {
    const pending = filenames.find(filename => !reviewed.includes(filename)) || null;
    return {
      reviewed: [...reviewed],
      reviewedCount: reviewed.length,
      total: filenames.length,
      nextFilename: pending,
      ...(newHead ? { newHead: true } : {}),
    };
  }

  function markReviewed(filename) {
    if (filenames.includes(filename) && !reviewed.includes(filename)) {
      reviewed.push(filename);
      reviewed = filenames.filter(item => reviewed.includes(item));
      try { storage.setItem(key, JSON.stringify(reviewed)); } catch (error) { /* local progress remains usable */ }
    }
    return snapshot();
  }

  return { snapshot, markReviewed };
}

createReviewController.renderDiffFile = renderDiffFile;
createReviewController.toggleDiff = toggleDiff;
createReviewController.createProgress = createProgress;

if (typeof module !== 'undefined' && module.exports) {
  module.exports = createReviewController;
}