name: companion-pr-check

# Soft, NON-BLOCKING warning: when a PR targeting staging/main declares a
# cross-repo "Companion:" PR, surface whether that companion is merged yet, so
# copilot and sim stay in lockstep (a change in one often needs the other).
#
# Declare in a PR description (repeatable; shorthand OR full URL both parse):
#   Companion: simstudioai/sim#1234
#   Companion: https://github.com/simstudioai/sim/pull/1234
#
# Requires a CROSS_REPO_TOKEN secret (fine-grained PAT with pull-requests:read on
# BOTH repos) to read the other repo's PR state. Without it the check still
# surfaces the declared link but reports "couldn't verify".

on:
  # PR-driven only: runs on the one PR being opened/edited/synced — no periodic
  # bulk scan. We assume companions are declared on BOTH sides, so the per-PR
  # trigger keeps each side's status fresh; to refresh after a companion merges,
  # re-edit the PR (or run this workflow manually via the Actions tab).
  pull_request:
    types: [opened, edited, reopened, synchronize]
    branches: [staging, main]
  workflow_dispatch: {}

permissions:
  pull-requests: write
  issues: write
  contents: read

jobs:
  companion:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/github-script@f28e40c7f34bde8b3046d885e986cb6290c5673b # v7
        env:
          CROSS_REPO_TOKEN: ${{ secrets.CROSS_REPO_TOKEN }}
        with:
          script: |
            const STICKY = '<!-- companion-pr-check -->';
            const { owner, repo } = context.repo;
            // Directional label: copilot/mothership PRs get "requires-sim-merge",
            // sim PRs get "requires-mothership-merge". Applied whenever the PR
            // declares a companion; removed when it declares none.
            const otherSide = repo === 'sim' ? 'mothership/copilot' : 'sim';
            const LABEL = repo === 'sim' ? 'requires-mothership-merge' : 'requires-sim-merge';
            const LABEL_DESC = `Has a companion PR on the ${otherSide} side — merge in lockstep`;
            const crossToken = process.env.CROSS_REPO_TOKEN;
            // Read the OTHER repo's PR via a plain REST fetch with the PAT in the
            // header — keeps the PAT strictly READ-ONLY and avoids re-instantiating
            // Octokit inside github-script (which can't require('@actions/github')).
            // Commenting/labeling uses the default GITHUB_TOKEN via `github`.
            async function crossGetPR(c) {
              const res = await fetch(`https://api.github.com/repos/${c.owner}/${c.repo}/pulls/${c.number}`, {
                headers: {
                  authorization: `Bearer ${crossToken}`,
                  accept: 'application/vnd.github+json',
                  'x-github-api-version': '2022-11-28',
                  'user-agent': 'companion-pr-check',
                },
              });
              if (!res.ok) { const e = new Error(`HTTP ${res.status}`); e.status = res.status; throw e; }
              return res.json();
            }

            // Two ways to declare a companion (either works; both feed this warning):
            //   1) a trailer anywhere:  Companion: owner/repo#N   (or a full PR URL)
            //   2) refs in a task list under a "## Companion..." heading — which ALSO
            //      renders a native live badge + progress bar on the PR (the "both" path):
            //        ## Companion PRs
            //        - [ ] owner/repo#N
            // Regexes are local + matchAll, so there's no shared lastIndex state to leak
            // between calls (stateless by construction).
            function parseCompanions(body) {
              body = body || '';
              const TRAILER = /Companion:\s*(?:https?:\/\/github\.com\/)?([\w.-]+)\/([\w.-]+)(?:\/pull\/|#)(\d+)/gi;
              const REF = /(?:https?:\/\/github\.com\/)?([\w.-]+)\/([\w.-]+)(?:\/pull\/|#)(\d+)/g;
              const out = [];
              const seen = new Set();
              const add = (o, r, n) => {
                const ref = `${o}/${r}#${n}`;
                if (seen.has(ref)) return;
                seen.add(ref);
                out.push({ owner: o, repo: r, number: Number(n), ref });
              };
              // (1) "Companion:" trailers anywhere in the body.
              for (const m of body.matchAll(TRAILER)) add(m[1], m[2], m[3]);
              // (2) refs in a task list under a "## Companion..." heading, until the next heading.
              let inSection = false;
              for (const line of body.split(/\r?\n/)) {
                if (/^#{1,6}\s/.test(line)) { inSection = /^#{1,6}\s*companion/i.test(line); continue; }
                if (!inSection) continue;
                for (const mm of line.matchAll(REF)) add(mm[1], mm[2], mm[3]);
              }
              return out;
            }

            async function findSticky(prNumber) {
              const comments = await github.paginate(github.rest.issues.listComments, {
                owner, repo, issue_number: prNumber, per_page: 100,
              });
              return comments.find((c) => (c.body || '').includes(STICKY));
            }
            async function upsert(prNumber, body) {
              const ex = await findSticky(prNumber);
              if (ex) await github.rest.issues.updateComment({ owner, repo, comment_id: ex.id, body });
              else await github.rest.issues.createComment({ owner, repo, issue_number: prNumber, body });
            }
            async function clear(prNumber) {
              const ex = await findSticky(prNumber);
              if (ex) await github.rest.issues.deleteComment({ owner, repo, comment_id: ex.id });
              // Drop the label too, so a PR edited to remove all companions doesn't
              // keep a stale badge. 404 (not present) is expected; surface anything else.
              try { await github.rest.issues.removeLabel({ owner, repo, issue_number: prNumber, name: LABEL }); }
              catch (e) { if (e.status !== 404) core.warning(`companion: removeLabel ${LABEL} on #${prNumber} failed (${e.status || e.message})`); }
            }
            async function ensureLabel() {
              try { await github.rest.issues.getLabel({ owner, repo, name: LABEL }); return; }
              catch (e) { if (e.status && e.status !== 404) { core.warning(`companion: getLabel ${LABEL} failed (${e.status})`); return; } }
              // 404 → label doesn't exist yet, create it. 422 = another run beat us (fine).
              try { await github.rest.issues.createLabel({ owner, repo, name: LABEL, color: 'd93f0b', description: LABEL_DESC }); }
              catch (e) { if (e.status !== 422) core.warning(`companion: createLabel ${LABEL} failed (${e.status || e.message})`); }
            }

            // staging PRs are a single feature → just this PR's body ("the one").
            // main (prod) release PRs bundle MANY feature PRs → aggregate the
            // companions declared on each squashed feature PR too, so "does any
            // commit in this release have a companion?" is answered.
            async function collectCompanions(pr) {
              const companions = parseCompanions(pr.body);
              const seen = new Set(companions.map((c) => c.ref));
              if (pr.base.ref === 'main') {
                let commits = [];
                try {
                  commits = await github.paginate(github.rest.pulls.listCommits, {
                    owner, repo, pull_number: pr.number, per_page: 100,
                  });
                } catch {}
                const featurePRs = new Set();
                const SQUASH = /\(#(\d+)\)/g; // squash-merge refs like "...(#306)"
                for (const c of commits) {
                  const msg = (c.commit && c.commit.message) || '';
                  let m;
                  SQUASH.lastIndex = 0;
                  while ((m = SQUASH.exec(msg)) !== null) featurePRs.add(Number(m[1]));
                }
                for (const n of featurePRs) {
                  if (n === pr.number) continue;
                  try {
                    const { data: fpr } = await github.rest.pulls.get({ owner, repo, pull_number: n });
                    for (const c of parseCompanions(fpr.body)) {
                      if (!seen.has(c.ref)) { seen.add(c.ref); companions.push(c); }
                    }
                  } catch {}
                }
              }
              return companions;
            }

            async function checkPR(pr) {
              const companions = await collectCompanions(pr);
              if (companions.length === 0) { await clear(pr.number); return; }
              await ensureLabel();
              try { await github.rest.issues.addLabels({ owner, repo, issue_number: pr.number, labels: [LABEL] }); }
              catch (e) { core.warning(`companion: addLabels ${LABEL} on #${pr.number} failed (${e.status || e.message})`); }

              const base = pr.base.ref;
              const lines = [];
              let warn = false;
              for (const c of companions) {
                if (!crossToken) {
                  lines.push(`- ❓ \`${c.ref}\` — set the **CROSS_REPO_TOKEN** secret to verify merge status`);
                  warn = true;
                  continue;
                }
                try {
                  const cp = await crossGetPR(c);
                  const title = (cp.title || '').slice(0, 80);
                  if (cp.merged) {
                    const tierOk = cp.base.ref === base;
                    lines.push(`- ${tierOk ? '✅' : '⚠️'} [\`${c.ref}\`](${cp.html_url}) — merged into \`${cp.base.ref}\`${tierOk ? '' : ` (this PR targets \`${base}\`)`} — ${title}`);
                    if (!tierOk) warn = true;
                  } else {
                    lines.push(`- ❌ [\`${c.ref}\`](${cp.html_url}) — **${String(cp.state).toUpperCase()}, not merged** (targets \`${cp.base.ref}\`) — ${title}`);
                    warn = true;
                  }
                } catch (e) {
                  lines.push(`- ❓ \`${c.ref}\` — couldn't read (${e.status || e.message}); check CROSS_REPO_TOKEN scope`);
                  warn = true;
                }
              }
              const heading = warn ? '## ⚠️ Cross-repo companion check' : '## ✅ Cross-repo companion check';
              const scope = base === 'main' ? ' (aggregated across the feature PRs in this release)' : '';
              const note = warn
                ? `One or more companion PRs aren't merged into \`${base}\` yet${scope}. Merging this without them will leave copilot and sim out of sync — merge them in lockstep.`
                : `All declared companion PRs are merged into \`${base}\`${scope}.`;
              await upsert(pr.number, `${STICKY}\n${heading}\n\n${note}\n\n${lines.join('\n')}`);
            }

            if (context.eventName === 'pull_request') {
              await checkPR(context.payload.pull_request);
            } else {
              // workflow_dispatch only: manual full re-scan of open staging/main PRs.
              for (const b of ['staging', 'main']) {
                const prs = await github.paginate(github.rest.pulls.list, { owner, repo, base: b, state: 'open', per_page: 100 });
                for (const pr of prs) await checkPR(pr);
              }
            }