// Handler for /lgtm, /hold, and /stageblog slash commands. Called by actions/github-script
// via `require(github.action_path + '/main.js')({ github, context, core })`.
// See action.yml for input wiring via env vars.

module.exports = async ({ github, context, core }) => {
  const { owner, repo } = context.repo;
  const approvedLabel = process.env.APPROVED_LABEL;
  const holdLabel = process.env.HOLD_LABEL;
  const alwaysAllowTeams = process.env.ALWAYS_ALLOW_TEAMS
    .split(',').map(s => s.trim()).filter(Boolean);
  const forceAllowTeams = process.env.FORCE_ALLOW_TEAMS
    .split(',').map(s => s.trim()).filter(Boolean);
  const codeownersPath = process.env.CODEOWNERS_PATH;
  const invalidateOnPush = process.env.INVALIDATE_ON_PUSH === 'true';
  const submitReview = process.env.SUBMIT_REVIEW === 'true';
  const autoMerge = process.env.ENABLE_AUTO_MERGE === 'true';
  const autoMergeMethod = process.env.AUTO_MERGE_METHOD.toUpperCase();
  const removeLabelsOnAccept = process.env.REMOVE_LABELS_ON_ACCEPT
    .split(',').map(s => s.trim()).filter(Boolean);
  const projectNumber = parseInt(process.env.PROJECT_NUMBER, 10) || 0;
  const projectStatusField = process.env.PROJECT_STATUS_FIELD;
  const projectAcceptedOption = process.env.PROJECT_ACCEPTED_OPTION;
  const projectGateLabel = process.env.PROJECT_GATE_LABEL;
  const dependabotAutoApprove = process.env.DEPENDABOT_AUTO_APPROVE.trim();
  const dependabotAllowedFiles = process.env.DEPENDABOT_ALLOWED_FILES
    .split(',').map(s => s.trim()).filter(Boolean);
  const reviewMarker = '<!-- slash-commands-lgtm -->';
  // Marker for reviews submitted by the dependabot auto-approve mode. Kept
  // distinct from the /lgtm marker so logs/audits can tell them apart; push
  // invalidation dismisses reviews carrying either marker.
  const dependabotMarker = '<!-- slash-commands-dependabot-auto -->';
  const botReviewMarkers = [reviewMarker, dependabotMarker];

  function setResult(result, actor) {
    core.setOutput('result', result);
    core.setOutput('actor', actor || '');
    core.info(`Result: ${result}${actor ? ` (actor: ${actor})` : ''}`);
  }

  // --- CODEOWNERS pattern → regex ---------------------------------
  // Supports: leading-/ anchoring, trailing-/ directory match,
  // `**` (any depth), `*` (single segment), `?`. No `!` negation.
  function patternToRegex(pattern) {
    let p = pattern;
    const anchored = p.startsWith('/');
    if (anchored) p = p.slice(1);
    const dirMatch = p.endsWith('/');
    if (dirMatch) p = p.slice(0, -1);
    // Escape regex meta chars except our glob tokens * and ?
    let re = p.replace(/[.+^${}()|[\]\\]/g, '\\$&');
    // Handle globs. Use placeholders so single-* replacement doesn't
    // catch ** sequences. `**/` = zero or more directories.
    re = re.replace(/\*\*\//g, '\u0001');
    re = re.replace(/\*\*/g, '\u0000');
    re = re.replace(/\*/g, '[^/]*');
    re = re.replace(/\?/g, '[^/]');
    re = re.replace(/\u0001/g, '(?:.*/)?');
    re = re.replace(/\u0000/g, '.*');
    // Anchoring: leading `/` → match from repo root; otherwise
    // match at any path depth (start or after a `/`).
    const prefix = anchored ? '^' : '(^|/)';
    // Trailing `/` → directory prefix (match anything under it).
    // Otherwise must match to end of string.
    const suffix = dirMatch ? '/.*$' : '$';
    return new RegExp(prefix + re + suffix);
  }

  function parseCodeowners(content) {
    const rules = [];
    for (const raw of content.split('\n')) {
      const line = raw.replace(/#.*$/, '').trim();
      if (!line) continue;
      const parts = line.split(/\s+/);
      const pattern = parts[0];
      const owners = parts.slice(1);
      if (!owners.length) continue;
      rules.push({ regex: patternToRegex(pattern), owners });
    }
    return rules;
  }

  function ownersForFile(rules, file) {
    // Last match wins.
    let owners = null;
    for (const r of rules) {
      if (r.regex.test(file)) owners = r.owners;
    }
    return owners || [];
  }

  // --- Auth helpers -----------------------------------------------
  const teamMembershipCache = new Map();
  async function isTeamMember(user, teamSlug) {
    const key = `${teamSlug}:${user}`;
    if (teamMembershipCache.has(key)) return teamMembershipCache.get(key);
    let ok;
    try {
      const { data } = await github.rest.teams.getMembershipForUserInOrg({
        org: owner, team_slug: teamSlug, username: user,
      });
      ok = data.state === 'active';
    } catch (e) {
      if (e.status === 404) {
        ok = false;
      } else if (e.status === 403) {
        core.warning(`Team membership check for @${owner}/${teamSlug} returned 403 — the provided github-token likely lacks Organization Members:read. Treating as not-a-member.`);
        ok = false;
      } else {
        throw e;
      }
    }
    teamMembershipCache.set(key, ok);
    return ok;
  }

  async function isInAlwaysAllowTeam(user) {
    for (const team of alwaysAllowTeams) {
      if (await isTeamMember(user, team)) {
        core.info(`@${user} authorized via always-allow team @${owner}/${team}`);
        return true;
      }
    }
    return false;
  }

  async function lastLabeledBy(prNumber, labelName) {
    const events = await github.paginate(github.rest.issues.listEvents, {
      owner, repo, issue_number: prNumber, per_page: 100,
    });
    let actor = null;
    for (const e of events) {
      if (e.event === 'labeled' && e.label?.name === labelName) actor = e.actor;
    }
    return actor;
  }

  async function isAuthorized(user, pr) {
    // 1. always-allow teams
    if (await isInAlwaysAllowTeam(user)) return true;
    // 2. CODEOWNERS of the PR's changed files (from BASE ref)
    let content;
    try {
      const { data } = await github.rest.repos.getContent({
        owner, repo, path: codeownersPath, ref: pr.base.ref,
      });
      content = Buffer.from(data.content, data.encoding).toString('utf8');
    } catch (e) {
      if (e.status === 404) {
        core.info(`No CODEOWNERS found at ${codeownersPath} on ${pr.base.ref}`);
        return false;
      }
      throw e;
    }
    const rules = parseCodeowners(content);
    const files = await github.paginate(github.rest.pulls.listFiles, {
      owner, repo, pull_number: pr.number, per_page: 100,
    });
    const ownerSet = new Set();
    for (const f of files) {
      for (const o of ownersForFile(rules, f.filename)) ownerSet.add(o);
    }
    core.info(`CODEOWNERS for this PR's files: ${[...ownerSet].join(', ') || '(none)'}`);
    for (const o of ownerSet) {
      if (o.includes('/')) {
        // @org/team — we require the org to match our repo's org
        const [oOrg, oTeam] = o.replace(/^@/, '').split('/');
        if (oOrg.toLowerCase() !== owner.toLowerCase()) continue;
        if (await isTeamMember(user, oTeam)) {
          core.info(`@${user} authorized via CODEOWNER team ${o}`);
          return true;
        }
      } else {
        // @user
        if (o.replace(/^@/, '').toLowerCase() === user.toLowerCase()) {
          core.info(`@${user} authorized via CODEOWNER user entry`);
          return true;
        }
      }
    }
    return false;
  }

  // --- Label & review helpers -------------------------------------
  async function addLabel(prNumber, label) {
    await github.rest.issues.addLabels({
      owner, repo, issue_number: prNumber, labels: [label],
    });
  }
  async function removeLabel(prNumber, label) {
    try {
      await github.rest.issues.removeLabel({
        owner, repo, issue_number: prNumber, name: label,
      });
    } catch (e) {
      if (e.status !== 404) throw e;
    }
  }
  async function react(commentId, content) {
    await github.rest.reactions.createForIssueComment({
      owner, repo, comment_id: commentId, content,
    });
  }
  async function submitApproval(prNumber, onBehalfOf, forced) {
    const via = forced ? '/lgtm force' : '/lgtm';
    await github.rest.pulls.createReview({
      owner, repo, pull_number: prNumber, event: 'APPROVE',
      body: `${reviewMarker}\nApproved on behalf of @${onBehalfOf} via \`${via}\`.`,
    });
  }
  async function dismissBotApprovals(prNumber, reason) {
    const reviews = await github.paginate(github.rest.pulls.listReviews, {
      owner, repo, pull_number: prNumber, per_page: 100,
    });
    for (const r of reviews) {
      if (r.state !== 'APPROVED') continue;
      if (!r.body || !botReviewMarkers.some(mk => r.body.includes(mk))) continue;
      try {
        await github.rest.pulls.dismissReview({
          owner, repo, pull_number: prNumber, review_id: r.id,
          message: reason,
        });
      } catch (e) {
        core.warning(`Failed to dismiss review ${r.id}: ${e.message}`);
      }
    }
  }
  async function enableAutoMerge(prNodeId, prNumber) {
    if (!autoMerge) return;
    async function mergeDirect(reason) {
      core.info(`${reason} — merging directly`);
      try {
        await github.rest.pulls.merge({
          owner, repo, pull_number: prNumber,
          merge_method: autoMergeMethod.toLowerCase(),
        });
        core.info('Merged');
      } catch (e) {
        core.warning(`Direct merge failed: ${e.message}. If branch protection requires code-owner review, add this GitHub App to the ruleset bypass list.`);
      }
    }
    try {
      const result = await github.graphql(
        `mutation($id: ID!, $m: PullRequestMergeMethod!) {
          enablePullRequestAutoMerge(input: {pullRequestId: $id, mergeMethod: $m}) {
            pullRequest { autoMergeRequest { enabledAt } reviewDecision }
          }
        }`,
        { id: prNodeId, m: autoMergeMethod },
      );
      core.info(`Auto-merge enabled (${autoMergeMethod})`);
      // Auto-merge does not inherit the ruleset-bypass privileges of the
      // actor who enabled it — it only fires once the PR is clean for
      // everyone. If we submitted an approval and reviewDecision is still
      // REVIEW_REQUIRED, the bot's approval did not satisfy
      // require_code_owner_review (GitHub Apps cannot be team members), so
      // auto-merge will never fire. Merge directly instead — a direct merge
      // DOES use the bot's bypass.
      const decision = result.enablePullRequestAutoMerge.pullRequest.reviewDecision;
      if (submitReview && decision === 'REVIEW_REQUIRED') {
        return mergeDirect('Bot approval did not satisfy review requirement');
      }
    } catch (e) {
      const msg = e.message || String(e);
      // enablePullRequestAutoMerge rejects PRs that are already mergeable
      // ("clean status") because there is nothing to wait for.
      if (/clean status/i.test(msg)) {
        return mergeDirect('PR already mergeable');
      }
      core.warning(`Could not enable auto-merge: ${msg}`);
    }
  }
  async function disableAutoMerge(prNodeId) {
    if (!autoMerge) return;
    try {
      await github.graphql(
        `mutation($id: ID!) {
          disablePullRequestAutoMerge(input: {pullRequestId: $id}) {
            pullRequest { id }
          }
        }`,
        { id: prNodeId },
      );
      core.info('Auto-merge disabled');
    } catch (e) {
      core.info(`Auto-merge disable skipped: ${e.message}`);
    }
  }
  async function onAccept(pr) {
    for (const label of removeLabelsOnAccept) {
      await removeLabel(pr.number, label);
    }
    if (!projectNumber) return;
    if (projectGateLabel && !pr.labels.some(l => l.name === projectGateLabel)) {
      core.info(`Skipping project update — PR lacks '${projectGateLabel}' label`);
      return;
    }
    try {
      const lookup = await github.graphql(
        `query($org: String!, $num: Int!, $field: String!) {
          organization(login: $org) {
            projectV2(number: $num) {
              id
              field(name: $field) {
                ... on ProjectV2SingleSelectField { id options { id name } }
              }
            }
          }
        }`,
        { org: owner, num: projectNumber, field: projectStatusField },
      );
      const project = lookup.organization?.projectV2;
      if (!project) {
        return core.warning(`Project #${projectNumber} not found in org ${owner}`);
      }
      const field = project.field;
      if (!field?.id) {
        return core.warning(`Field '${projectStatusField}' not found (or not single-select) in project #${projectNumber}`);
      }
      const option = field.options.find(o => o.name === projectAcceptedOption);
      if (!option) {
        return core.warning(`Option '${projectAcceptedOption}' not found in field '${projectStatusField}'`);
      }
      // addProjectV2ItemById is idempotent — returns the existing item if
      // the PR is already in the project.
      const add = await github.graphql(
        `mutation($proj: ID!, $pr: ID!) {
          addProjectV2ItemById(input: {projectId: $proj, contentId: $pr}) {
            item { id }
          }
        }`,
        { proj: project.id, pr: pr.node_id },
      );
      const itemId = add.addProjectV2ItemById.item.id;
      await github.graphql(
        `mutation($proj: ID!, $item: ID!, $field: ID!, $opt: String!) {
          updateProjectV2ItemFieldValue(input: {
            projectId: $proj, itemId: $item, fieldId: $field,
            value: { singleSelectOptionId: $opt }
          }) { projectV2Item { id } }
        }`,
        { proj: project.id, item: itemId, field: field.id, opt: option.id },
      );
      core.info(`Moved PR to '${projectAcceptedOption}' in project #${projectNumber}`);
    } catch (e) {
      core.warning(`Project update failed: ${e.message}. Ensure the GitHub App has Organization Projects:write permission.`);
    }
  }

  // --- Dependabot auto-approve -------------------------------------
  // Opt-in via `dependabot-auto-approve`. Approves, labels, and enables
  // auto-merge on Dependabot PRs — but ONLY when every gate below holds.
  // Any gate failure exits without approving (fail closed), logging why.

  // The real Dependabot app's login and stable numeric user id. Checking the
  // id means a lookalike account (e.g. a renamed user squatting a similar
  // login) can never match.
  const DEPENDABOT_LOGIN = 'dependabot[bot]';
  const DEPENDABOT_USER_ID = 49699333;

  // Parse Dependabot's structured metadata block from a commit message:
  //   updated-dependencies:
  //   - dependency-name: foo
  //     dependency-type: direct:development
  //     update-type: version-update:semver-patch
  // Returns one entry per updated dependency; fields are undefined when the
  // corresponding line is absent. Empty array = no metadata block found.
  function parseDependabotMetadata(message) {
    const entries = [];
    let inBlock = false;
    let current = null;
    for (const raw of message.split('\n')) {
      const line = raw.replace(/\r$/, '');
      if (!inBlock) {
        if (/^updated-dependencies:\s*$/.test(line)) inBlock = true;
        continue;
      }
      const name = line.match(/^-\s+dependency-name:\s*["']?(.+?)["']?\s*$/);
      if (name) {
        current = { name: name[1] };
        entries.push(current);
        continue;
      }
      // Indented `key: value` lines belong to the current entry. Record the
      // two keys we gate on; tolerate others (e.g. dependency-group).
      const field = current && line.match(/^\s+([a-z-]+):\s*["']?(.+?)["']?\s*$/);
      if (field) {
        if (field[1] === 'dependency-type') current.dependencyType = field[2];
        if (field[1] === 'update-type') current.updateType = field[2];
        continue;
      }
      // Anything else (the `...` terminator, blank line, trailer) ends the block.
      inBlock = false;
      current = null;
    }
    return entries;
  }

  // Evaluate one PR against the auto-approve policy. Returns true only if it
  // was approved on this call.
  async function handleDependabotAutoApprove(prNumber) {
    const skip = (reason) => {
      core.info(`dependabot-auto-approve: PR #${prNumber} not approved — ${reason}`);
      return false;
    };

    const { data: pr } = await github.rest.pulls.get({ owner, repo, pull_number: prNumber });

    // PR must be open, non-draft, without merge conflicts, and not held.
    if (pr.state !== 'open') return skip('PR is not open');
    if (pr.draft) return skip('PR is a draft');
    if (pr.mergeable_state === 'dirty') return skip('PR has merge conflicts');
    if (pr.labels.some(l => l.name === holdLabel)) return skip(`PR has the '${holdLabel}' label`);

    // 1. Author must be the real Dependabot app — login AND user id.
    if (pr.user.login !== DEPENDABOT_LOGIN || pr.user.id !== DEPENDABOT_USER_ID) {
      return skip(`author is @${pr.user.login} (id ${pr.user.id}), not ${DEPENDABOT_LOGIN} (id ${DEPENDABOT_USER_ID})`);
    }

    // 2. Same-repo head on a dependabot/ branch — never fork PRs.
    if (pr.head.repo?.full_name !== pr.base.repo.full_name) {
      return skip('head repo is not the base repo');
    }
    if (!pr.head.ref.startsWith('dependabot/')) {
      return skip(`head ref '${pr.head.ref}' is not a dependabot/ branch`);
    }

    // 3. Every commit must carry a verified signature and be authored by
    // dependabot. Once a human pushes to the branch this gate fails for the
    // rest of the PR's life — by design (fail closed); push invalidation
    // dismisses the old approval and a maintainer must /lgtm from then on.
    const commits = await github.paginate(github.rest.pulls.listCommits, {
      owner, repo, pull_number: prNumber, per_page: 100,
    });
    if (!commits.length) return skip('PR has no commits');
    for (const c of commits) {
      if (c.commit?.verification?.verified !== true) {
        return skip(`commit ${c.sha.slice(0, 7)} does not have a verified signature`);
      }
      if (c.author?.login !== DEPENDABOT_LOGIN) {
        return skip(`commit ${c.sha.slice(0, 7)} authored by @${c.author?.login || '(unknown)'}, not ${DEPENDABOT_LOGIN}`);
      }
    }

    // 4. Changed files must be a subset of the allow-list (exact paths).
    // Renames are checked on both sides.
    const files = await github.paginate(github.rest.pulls.listFiles, {
      owner, repo, pull_number: prNumber, per_page: 100,
    });
    for (const f of files) {
      if (!dependabotAllowedFiles.includes(f.filename)) {
        return skip(`changed file '${f.filename}' is not in dependabot-allowed-files`);
      }
      if (f.previous_filename && !dependabotAllowedFiles.includes(f.previous_filename)) {
        return skip(`renamed file '${f.previous_filename}' is not in dependabot-allowed-files`);
      }
    }

    // 5. Scope: under 'dev-patch-minor', every updated dependency (from the
    // structured metadata in the commit messages — trustworthy here because
    // gate 3 proved the messages are dependabot-authored and signed) must be
    // direct:development with a semver-patch or semver-minor update. Missing
    // or unparseable metadata never approves.
    const deps = [];
    for (const c of commits) deps.push(...parseDependabotMetadata(c.commit.message));
    if (!deps.length) return skip('no updated-dependencies metadata found in commit messages');
    for (const d of deps) {
      if (d.dependencyType !== 'direct:development') {
        return skip(`'${d.name}' has dependency-type '${d.dependencyType || '(missing)'}' — mode dev-patch-minor requires direct:development`);
      }
      if (!['version-update:semver-patch', 'version-update:semver-minor'].includes(d.updateType)) {
        return skip(`'${d.name}' has update-type '${d.updateType || '(missing)'}' — mode dev-patch-minor requires semver-patch or semver-minor`);
      }
    }

    // 6. CI must be green on the current head SHA: every check run completed
    // with a passing conclusion, at least one non-skipped check exists (no
    // approval without CI evidence), and the combined commit status — if any
    // statuses exist — is success. Pending checks exit silently; the next
    // check_suite completion re-evaluates. This gate lives here rather than
    // in branch protection so approval itself is withheld until CI passes.
    const checkRuns = await github.paginate(github.rest.checks.listForRef, {
      owner, repo, ref: pr.head.sha, per_page: 100,
    });
    const passing = ['success', 'neutral', 'skipped'];
    for (const run of checkRuns) {
      if (run.status !== 'completed') {
        return skip(`check '${run.name}' is still ${run.status}`);
      }
      if (!passing.includes(run.conclusion)) {
        return skip(`check '${run.name}' concluded '${run.conclusion}'`);
      }
    }
    if (!checkRuns.some(r => r.conclusion !== 'skipped')) {
      return skip('no non-skipped check runs on the head SHA');
    }
    const { data: combined } = await github.rest.repos.getCombinedStatusForRef({
      owner, repo, ref: pr.head.sha,
    });
    if (combined.total_count > 0 && combined.state !== 'success') {
      return skip(`combined commit status is '${combined.state}'`);
    }

    // Idempotency: concurrent check_suite completions can race — skip if an
    // active (non-dismissed) auto-approval already exists.
    const reviews = await github.paginate(github.rest.pulls.listReviews, {
      owner, repo, pull_number: prNumber, per_page: 100,
    });
    if (reviews.some(r => r.state === 'APPROVED' && r.body?.includes(dependabotMarker))) {
      return skip('already auto-approved');
    }

    // All gates passed — mirror the /lgtm accept path with the distinct
    // marker, so push invalidation dismisses this approval too.
    await addLabel(prNumber, approvedLabel);
    await onAccept(pr);
    await github.rest.pulls.createReview({
      owner, repo, pull_number: prNumber, event: 'APPROVE',
      body: `${dependabotMarker}\nAutomatically approved under the \`${dependabotAutoApprove}\` Dependabot policy: `
        + 'all commits are dependabot-authored with verified signatures, changed files are within '
        + `\`${dependabotAllowedFiles.join(', ')}\`, every update is \`direct:development\` `
        + 'semver-patch/minor, and CI is green.',
    });
    await enableAutoMerge(pr.node_id, prNumber);
    core.info(`dependabot-auto-approve: PR #${prNumber} approved`);
    return true;
  }

  // --- Dispatch ---------------------------------------------------
  const ev = context.eventName;

  // Invalidation on push
  if (ev === 'pull_request_target' && context.payload.action === 'synchronize') {
    if (!invalidateOnPush) return setResult('noop');
    const pr = context.payload.pull_request;
    const hasApproved = pr.labels.some(l => l.name === approvedLabel);
    if (!hasApproved) return setResult('noop');
    // If a core/lead maintainer applied the label directly (not the bot via
    // /lgtm), treat it as a sticky governance decision rather than a per-SHA
    // approval. Check the union of always-allow + force-allow teams so lead
    // maintainers are covered even when always-allow-teams is narrower.
    const labeler = await lastLabeledBy(pr.number, approvedLabel);
    if (labeler && labeler.type !== 'Bot') {
      for (const team of [...alwaysAllowTeams, ...forceAllowTeams]) {
        if (await isTeamMember(labeler.login, team)) {
          core.info(`'${approvedLabel}' was applied manually by @${labeler.login} (member of @${owner}/${team}); skipping push invalidation.`);
          return setResult('invalidate-skipped', labeler.login);
        }
      }
    }
    await removeLabel(pr.number, approvedLabel);
    await dismissBotApprovals(pr.number, 'New commits pushed — approval invalidated.');
    await disableAutoMerge(pr.node_id);
    await github.rest.issues.createComment({
      owner, repo, issue_number: pr.number,
      body: `New commits were pushed — removed the \`${approvedLabel}\` label. Re-approve with \`/lgtm\`.`,
    });
    return setResult('invalidated');
  }

  // Dependabot auto-approve — evaluated when a PR opens/reopens and whenever
  // a check suite completes on a dependabot branch (the pass that usually
  // approves, since CI is rarely finished at open time).
  const isDependabotEvent =
    (ev === 'pull_request_target' && ['opened', 'reopened'].includes(context.payload.action)) ||
    (ev === 'check_suite' && context.payload.action === 'completed');
  if (isDependabotEvent) {
    if (!dependabotAutoApprove) return setResult('noop');
    if (dependabotAutoApprove !== 'dev-patch-minor') {
      core.warning(`Unknown dependabot-auto-approve mode '${dependabotAutoApprove}' — auto-approve disabled (fail closed).`);
      return setResult('noop');
    }
    const prNumbers = [];
    if (ev === 'check_suite') {
      const suite = context.payload.check_suite;
      const branch = suite.head_branch || '';
      // Only same-repo dependabot/ branches can ever pass the gates — skip
      // the API round-trips entirely for everything else.
      if (!branch.startsWith('dependabot/')) return setResult('noop');
      for (const p of suite.pull_requests || []) prNumbers.push(p.number);
      if (!prNumbers.length) {
        // pull_requests can be empty on some deliveries — resolve by branch.
        const { data: prs } = await github.rest.pulls.list({
          owner, repo, state: 'open', head: `${owner}:${branch}`, per_page: 10,
        });
        for (const p of prs) prNumbers.push(p.number);
      }
    } else {
      prNumbers.push(context.payload.pull_request.number);
    }
    let approvedCount = 0;
    for (const n of prNumbers) {
      if (await handleDependabotAutoApprove(n)) approvedCount++;
    }
    return setResult(approvedCount ? 'dependabot-approved' : 'dependabot-skipped');
  }

  // Comment commands
  if (ev !== 'issue_comment') return setResult('noop');
  if (!context.payload.issue.pull_request) return setResult('noop');

  const commentBody = context.payload.comment.body || '';
  const commentId = context.payload.comment.id;
  const actor = context.payload.comment.user.login;
  const firstLine = commentBody.split('\n')[0].trim();
  const m = firstLine.match(/^\/(lgtm|hold|unhold|stageblog)\b\s*(cancel|force)?\s*$/i);
  if (!m) return setResult('noop', actor);

  const cmd = m[1].toLowerCase();
  const arg = (m[2] || '').toLowerCase();
  const cancel = arg === 'cancel' || cmd === 'unhold';
  // `force` is only meaningful for /lgtm — reject `/hold force` etc. as noop
  // rather than silently treating it as the base command.
  if (arg === 'force' && cmd !== 'lgtm') return setResult('noop', actor);
  const force = arg === 'force';

  const prNumber = context.payload.issue.number;
  const { data: pr } = await github.rest.pulls.get({ owner, repo, pull_number: prNumber });
  if (pr.state !== 'open') return setResult('noop', actor);

  // /lgtm force — restricted to force-allow-teams. Bypasses the self-approval
  // guard and the CODEOWNERS path entirely; only team membership grants this.
  if (cmd === 'lgtm' && force) {
    let allowed = false;
    for (const team of forceAllowTeams) {
      if (await isTeamMember(actor, team)) { allowed = true; break; }
    }
    if (!allowed) {
      await react(commentId, '-1');
      return setResult('force-unauthorized', actor);
    }
    await addLabel(prNumber, approvedLabel);
    await onAccept(pr);
    if (submitReview) await submitApproval(prNumber, actor, true);
    await react(commentId, '+1');
    await enableAutoMerge(pr.node_id, prNumber);
    return setResult('lgtm-forced', actor);
  }

  // Self-approval guard (only for /lgtm, not /hold)
  if (cmd === 'lgtm' && !cancel && actor.toLowerCase() === pr.user.login.toLowerCase()) {
    await react(commentId, '-1');
    return setResult('self-lgtm-blocked', actor);
  }

  // Auth check. /lgtm is restricted to always-allow-teams (core maintainers)
  // only — CODEOWNERS does not grant it. /hold and /stageblog still accept
  // CODEOWNERS of the PR's changed files.
  const authorized = cmd === 'lgtm'
    ? await isInAlwaysAllowTeam(actor)
    : await isAuthorized(actor, pr);
  if (!authorized) {
    await react(commentId, '-1');
    return setResult('unauthorized', actor);
  }

  // /stageblog — dispatch a caller-defined workflow with pinned head SHA
  if (cmd === 'stageblog') {
    const stageblogWorkflow = process.env.STAGEBLOG_WORKFLOW;
    if (!stageblogWorkflow) {
      await react(commentId, 'confused');
      return setResult('stageblog-disabled', actor);
    }
    // cancel is meaningless here — just ignore silently
    if (cancel) return setResult('noop', actor);

    // Ack early — listFiles pagination + workflow dispatch can take a few
    // seconds and the commenter otherwise gets no feedback until then.
    await react(commentId, 'eyes');

    // Gate: PR must touch blog paths
    const blogRegexes = process.env.STAGEBLOG_PATHS
      .split(',').map(s => s.trim()).filter(Boolean).map(patternToRegex);
    const files = await github.paginate(github.rest.pulls.listFiles, {
      owner, repo, pull_number: prNumber, per_page: 100,
    });
    const touchesBlog = files.some(f => blogRegexes.some(r => r.test(f.filename)));
    if (!touchesBlog) {
      await react(commentId, '-1');
      await github.rest.issues.createComment({
        owner, repo, issue_number: prNumber,
        body: `\`/stageblog\` refused — this PR does not touch any blog paths (\`${process.env.STAGEBLOG_PATHS}\`).`,
      });
      return setResult('stageblog-not-blog', actor);
    }

    // Dispatch — pin head SHA at time of comment
    const headSha = pr.head.sha;
    await github.rest.actions.createWorkflowDispatch({
      owner, repo, workflow_id: stageblogWorkflow, ref: pr.base.ref,
      inputs: { pr_number: String(prNumber), head_sha: headSha },
    });
    await react(commentId, 'rocket');
    await github.rest.issues.createComment({
      owner, repo, issue_number: prNumber,
      body: `Blog staging triggered by @${actor} for \`${headSha.slice(0, 7)}\`. Watch the [**${stageblogWorkflow}** workflow](../actions/workflows/${stageblogWorkflow}) for the preview link.`,
    });
    return setResult('stageblog-dispatched', actor);
  }

  // Execute
  if (cmd === 'lgtm' && !cancel) {
    await addLabel(prNumber, approvedLabel);
    await onAccept(pr);
    if (submitReview) await submitApproval(prNumber, actor);
    await react(commentId, '+1');
    await enableAutoMerge(pr.node_id, prNumber);
    return setResult('lgtm-added', actor);
  }
  if (cmd === 'lgtm' && cancel) {
    await removeLabel(prNumber, approvedLabel);
    await dismissBotApprovals(prNumber, `@${actor} cancelled approval via /lgtm cancel.`);
    await disableAutoMerge(pr.node_id);
    await react(commentId, '+1');
    return setResult('lgtm-removed', actor);
  }
  if ((cmd === 'hold' && !cancel)) {
    await addLabel(prNumber, holdLabel);
    await react(commentId, '+1');
    return setResult('hold-added', actor);
  }
  // /hold cancel or /unhold
  await removeLabel(prNumber, holdLabel);
  await react(commentId, '+1');
  return setResult('hold-removed', actor);
};