function createReviewController({ fetchJson }) {
  let pendingSubmission = null;

  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' } });
  }

  function submit(item, payload) {
    if (pendingSubmission) return pendingSubmission;
    pendingSubmission = fetchJson(endpoint(item), {
      method: 'POST',
      headers: { Accept: 'application/json', 'Content-Type': 'application/json' },
      body: JSON.stringify(payload),
    }).finally(() => { pendingSubmission = null; });
    return pendingSubmission;
  }

  return { load, submit };
}

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 +
    '<label class="small" for="review-note-' + index + '">Note for ' + filename + '</label>' +
    '<textarea class="review-note" id="review-note-' + index + '" data-review-filename="' + filename + '" placeholder="Capture feedback for this file"></textarea>' +
    '<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();
  }

  function clear() {
    reviewed = [];
    newHead = false;
    try { storage.removeItem(key); } catch (error) { /* cleared in memory */ }
    return snapshot();
  }

  return { snapshot, markReviewed, clear };
}

function createDraft({ storage, repository, number, headSha, files }) {
  const filenames = (files || []).map(file => file && file.filename).filter(Boolean);
  const key = 'stackchain.review-draft.v1:' + repository + '#' + number + '@' + headSha;
  let draft = { notes: {}, summary: '', decision: 'comment' };
  try {
    const saved = JSON.parse(storage.getItem(key) || '{}');
    if (saved && typeof saved === 'object') {
      draft.notes = Object.fromEntries(filenames
        .filter(filename => typeof saved.notes?.[filename] === 'string' && saved.notes[filename])
        .map(filename => [filename, saved.notes[filename]]));
      if (typeof saved.summary === 'string') draft.summary = saved.summary;
      if (['comment', 'approve', 'request_changes'].includes(saved.decision)) {
        draft.decision = saved.decision;
      }
    }
  } catch (error) { /* start with an empty in-memory draft */ }

  function persist() {
    try { storage.setItem(key, JSON.stringify(draft)); } catch (error) { /* draft remains usable */ }
  }

  function snapshot() {
    return { notes: { ...draft.notes }, summary: draft.summary, decision: draft.decision };
  }

  function setNote(filename, note) {
    if (!filenames.includes(filename)) return snapshot();
    if (String(note)) draft.notes[filename] = String(note);
    else delete draft.notes[filename];
    persist();
    return snapshot();
  }

  function setSummary(summary) {
    draft.summary = String(summary || '');
    persist();
    return snapshot();
  }

  function setDecision(decision) {
    if (['comment', 'approve', 'request_changes'].includes(decision)) {
      draft.decision = decision;
      persist();
    }
    return snapshot();
  }

  function clear() {
    draft = { notes: {}, summary: '', decision: 'comment' };
    try { storage.removeItem(key); } catch (error) { /* cleared in memory */ }
    return snapshot();
  }

  return { snapshot, setNote, setSummary, setDecision, clear };
}

function formatFeedback(draft, files) {
  const decisions = {
    comment: 'Comment',
    approve: 'Approve',
    request_changes: 'Request changes',
  };
  const sections = [
    '## Intended decision\n' + (decisions[draft.decision] || decisions.comment),
  ];
  if (String(draft.summary || '').trim()) {
    sections.push('## Summary\n' + String(draft.summary).trim());
  }
  const fileNotes = (files || []).flatMap(file => {
    const filename = file && file.filename;
    const note = filename && String(draft.notes?.[filename] || '').trim();
    if (!note) return [];
    return ['### `' + String(filename).replaceAll('`', '\\`') + '`\n' + note];
  });
  if (fileNotes.length) sections.push('## File notes\n' + fileNotes.join('\n\n'));
  return sections.join('\n\n');
}

async function copyAndContinue({ text, url, copy, open, fallback }) {
  const destination = open();
  try {
    await copy(text);
  } catch (error) {
    destination?.close?.();
    fallback(text);
    return { copied: false, opened: false };
  }
  if (!destination) {
    fallback(text);
    return { copied: true, opened: false };
  }
  destination.location.href = url;
  return { copied: true, opened: true };
}

createReviewController.renderDiffFile = renderDiffFile;
createReviewController.toggleDiff = toggleDiff;
createReviewController.createProgress = createProgress;
createReviewController.createDraft = createDraft;
createReviewController.formatFeedback = formatFeedback;
createReviewController.copyAndContinue = copyAndContinue;

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