vikunja/.github/workflows/preview.yml

name: Preview

on:
  # pull_request_target gives write access to GHCR even for PRs from forks.
  # This is safe because:
  # 1. We explicitly checkout the PR's head commit (no base branch code execution)
  # 2. We ONLY build a Docker image (isolated container, no workflow scripts from PR)
  # 3. The github-script step only uses safe PR metadata (number, SHA) — no PR-supplied
  #    text (title, body, commit messages) is interpolated, so there is no injection risk
  # 4. Build happens in isolated Docker container with well-defined Dockerfile
  pull_request_target:

jobs:
  docker:
    runs-on: ubuntu-latest
    permissions:
      packages: write
      contents: read
      pull-requests: write
    steps:
      - name: Free Disk Space
        uses: jlumbroso/free-disk-space@54081f138730dfa15788a46383842cd2f914a1be # v1.3.1
        with:
          large-packages: false
          docker-images: false
          swap-storage: false
      - name: Checkout
        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
        with:
          # For pull_request_target, we need to explicitly fetch the PR ref from forks
          # since the PR's commit SHA is not reachable in the base repository.
          # This is safe because no PR code is executed in workflow context.
          # Only Docker build uses the PR code (isolated in container).
          ref: refs/pull/${{ github.event.pull_request.number }}/head
      - name: Git describe
        id: ghd
        uses: proudust/gh-describe@v2
      - name: Login to GHCR
        uses: docker/login-action@5e57cd118135c172c3672efd75eb46360885c0ef # v3
        with:
          registry: ghcr.io
          username: ${{ github.repository_owner }}
          password: ${{ secrets.GITHUB_TOKEN }}
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@8d2750c68a42422c14e847fe6c8ac0403b4cbd6f # v3
        with:
          version: latest
      - name: Docker meta
        id: meta
        uses: docker/metadata-action@c299e40c65443455700f0fdfc63efafe5b349051 # v5
        with:
          images: ghcr.io/${{ github.repository_owner }}/${{ github.event.repository.name }}
          tags: |
            type=ref,event=pr
            type=sha,format=long            
      - name: Build and push PR image
        uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6
        with:
          context: .
          platforms: linux/amd64
          push: true
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha
          cache-to: type=gha,mode=max
          build-args: |
            RELEASE_VERSION=${{ steps.ghd.outputs.describe }}            
      - name: Comment on PR
        uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8
        with:
          script: |
            const prNumber = context.payload.pull_request.number;
            const fullSha = context.payload.pull_request.head.sha;
            const shortSha = fullSha.substring(0, 7);
            const base = 'preview.vikunja.dev';
            const image = `ghcr.io/${{ github.repository_owner }}/${{ github.event.repository.name }}`;
            const marker = '<!-- vikunja-preview-comment -->';
            const shaMarker = '<!-- sha-rows -->';
            const shaMarkerEnd = '<!-- /sha-rows -->';

            const prTag = `pr-${prNumber}`;
            const shaTag = `sha-${fullSha}`;
            const newShaRow = `| https://${shaTag}.${base} | \`${image}:${shaTag}\` | \`${shortSha}\` |`;

            // Collect previous SHA rows from existing comment
            let previousShaRows = [];
            const { data: comments } = await github.rest.issues.listComments({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: prNumber,
            });
            const existing = comments.find(c => c.body.includes(marker));

            if (existing) {
              const match = existing.body.match(
                new RegExp(`${shaMarker}\\n([\\s\\S]*?)\\n${shaMarkerEnd}`)
              );
              if (match) {
                previousShaRows = match[1]
                  .split('\n')
                  .map(l => l.trim())
                  .filter(l => l.startsWith('|'));
              }
            }

            // Remove duplicate if this SHA was already recorded
            previousShaRows = previousShaRows.filter(r => !r.includes(shaTag));

            const allShaRows = [newShaRow, ...previousShaRows].join('\n');

            const body = [
              marker,
              `### Preview Deployment`,
              ``,
              `Preview deployments for this PR are available at:`,
              ``,
              `| URL | Tag | Commit |`,
              `| --- | --- | --- |`,
              `| https://${prTag}.${base} | \`${image}:${prTag}\` | latest |`,
              shaMarker,
              allShaRows,
              shaMarkerEnd,
              ``,
              `The preview environment will start automatically on first visit. Subsequent pushes to this PR will update the \`${prTag}\` image — the preview picks up the new version on restart. The per-commit URLs point to a specific version and will not change.`,
              ``,
              `<details>`,
              `<summary>Run locally with Docker</summary>`,
              ``,
              '```bash',
              `docker pull ${image}:${prTag}`,
              `docker run -p 3456:3456 ${image}:${prTag}`,
              '```',
              `</details>`,
              ``,
              `_Last updated for commit ${shortSha}_`,
            ].join('\n');

            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: prNumber,
                body,
              });
            }