preview-link.yml

name: Post preview link

# Cloudflare Pages reports previews as a Check Run, not a GitHub Deployment, so
# deployment_status never fires here. Instead we key off the comment Cloudflare
# posts on the PR — it carries the branch preview URL — and reply with the exact
# post URL (branch preview + /blog/<slug>/). Free: GitHub's built-in token, no secrets.
on:
  issue_comment:
    types: [created, edited]

permissions:
  pull-requests: write
  contents: read

jobs:
  comment:
    # Only Cloudflare's deploy comment, and only on pull requests.
    if: >
      github.event.issue.pull_request &&
      startsWith(github.event.comment.user.login, 'cloudflare-workers-and-pages') &&
      contains(github.event.comment.body, 'Deploy successful')
    runs-on: ubuntu-latest
    steps:
      - uses: actions/github-script@v7
        with:
          script: |
            const cf = context.payload.comment.body || '';

            // Prefer the branch preview URL (stable across redeploys of this branch);
            // fall back to the per-deploy hash URL if only that is present.
            const branch = cf.match(/Branch Preview URL:[\s\S]*?(https:\/\/[a-z0-9-]+\.[a-z0-9-]+\.pages\.dev)/i);
            const hash = cf.match(/Preview URL:[\s\S]*?(https:\/\/[a-z0-9-]+\.[a-z0-9-]+\.pages\.dev)/i);
            const base = (branch && branch[1]) || (hash && hash[1]);
            if (!base) return;

            const pr = context.payload.issue;
            const match = (pr.body || '').match(/<!--\s*post-slug:\s*([a-z0-9-]+)\s*-->/);
            const link = match ? `${base}/blog/${match[1]}` : base;

            const marker = '<!-- preview-link-bot -->';
            const body = `${marker}\n> [!TIP]\n> 📄 **[Preview your post →](${link})**`;

            const comments = await github.rest.issues.listComments({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: pr.number,
            });
            const existing = comments.data.find((c) => (c.body || '').includes(marker));
            if (existing) {
              await github.rest.issues.updateComment({
                owner: context.repo.owner,
                repo: context.repo.repo,
                comment_id: existing.id,
                body,
              });
            } else {
              await github.rest.issues.createComment({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: pr.number,
                body,
              });
            }