upload-preview.yml

name: Upload Preview
on:
  workflow_run:
    workflows: [Preview]
    types:
    - completed
jobs:
  upload:
    name: Upload
    runs-on: ubuntu-latest
    permissions:
      contents: 'read'
      id-token: 'write'
      issues: 'write'
      pull-requests: 'write'
    if: ${{ github.event.workflow_run.conclusion == 'success' }}
    steps:
    - uses: actions/checkout@v4
      with:
        fetch-depth: 2
    - name: Authenticate to Google Cloud
      uses: google-github-actions/auth@v2
      with:
        workload_identity_provider: 'projects/28141583151/locations/global/workloadIdentityPools/github/providers/github-actions'
        service_account: 'github@spec-previews.iam.gserviceaccount.com'
    - name: Fetch artifact
      uses: actions/github-script@v7
      with:
        script: |
          const fs = require('fs');
          const allArtifacts = await github.rest.actions.listWorkflowRunArtifacts({
            ...context.repo,
            run_id: context.payload.workflow_run.id
          });
          let artifact = allArtifacts.data.artifacts.find(
              artifact => artifact.name === "upload-compressed");
          if (!artifact)
            process.exit(1);
          let download = await github.rest.actions.downloadArtifact({
            ...context.repo,
            artifact_id: artifact.id,
            archive_format: 'zip',
          });
          fs.writeFileSync(`${process.env.GITHUB_WORKSPACE}/upload-compressed.zip`, Buffer.from(download.data));
    - name: Unzip artifact
      shell: bash
      run: |
        mkdir -p upload-compressed
        unzip upload-compressed.zip -d upload-compressed
        size=`du --summarize --block-size=1K upload-compressed | cut -f1`
        if [[ "$size" -gt 4096 ]]; then
          echo "Too large (was $size kilobytes)." >&2
          exit 1
        fi
        pull_number="$(cat upload-compressed/.pull-number)"
        if ! [[ "$pull_number" =~ ^[0-9]+$ ]]; then
          echo "Invalid pull request number." >&2
          exit 1
        fi
        echo "PULL_NUMBER=$pull_number" >> $GITHUB_ENV
    - name: Upload to Google Cloud Storage
      uses: google-github-actions/upload-cloud-storage@v0
      with:
        path: upload-compressed
        glob: "**/*.html"
        destination: "spec-previews/${{ github.repository }}/pull/${{ env.PULL_NUMBER }}"
        parent: false
        gzip: false
        headers: |-
          content-type: text/html; charset=UTF-8
          content-encoding: br
          cache-control: no-transform, max-age=30
    - name: Post comment
      uses: actions/github-script@v7
      env:
        GCS_BASE: "spec-previews/${{ github.repository }}/pull/${{ env.PULL_NUMBER }}"
      with:
        script: |
          const fs = require("fs");
          const baseUrl = `https://storage.googleapis.com/${process.env.GCS_BASE}`;
          let body = "<!-- preview-magic-74656 -->Preview:";
          for (let headFile of await fs.promises.readdir("upload-compressed/head")) {
            if (!headFile.endsWith('.html')) continue;
            body += `\n- [${headFile}](${baseUrl}/head/${headFile})`;
            const extraLinks =
                (await Promise.all(
                    ["diff", "base"]
                    .map(k => fs.promises.access(`upload-compressed/${k}/${headFile}`)
                              .then(() => [`[${k}](${baseUrl}/${k}/${headFile})`], () => []))))
                .flat();
            if (extraLinks.length)
                body += ` (${extraLinks.join(" ")})`;
          }
          console.log(body);
          const issue = {...context.repo, issue_number: process.env.PULL_NUMBER};
          const comments = await github.paginate(
              github.rest.issues.listComments.endpoint.merge({...issue}));
          let comment = comments.find(
              comment => comment.body.includes("<!-- preview-magic-74656 -->"));
          if (comment) {
            await github.rest.issues.updateComment({...issue, comment_id: comment.id, body});
          } else {
            await github.rest.issues.createComment({...issue, body});
          }