artifacts.yml

name: Post build artifact links

# Runs in the context of the base (upstream) repo after the build workflow
# completes — this gives the GITHUB_TOKEN write access to PRs even when
# the build was triggered by a fork PR.
on:
  workflow_run:
    workflows: ["C/C++ CI"]
    types: [completed]

permissions:
  actions: read
  pull-requests: write

jobs:
  post-artifacts:
    if: >
      github.event.workflow_run.event == 'pull_request' &&
      github.event.workflow_run.conclusion == 'success'
    runs-on: ubuntu-latest
    steps:
    - name: Comment artifact links on PR
      uses: actions/github-script@v7
      with:
        script: |
          const run = context.payload.workflow_run;
          const runUrl = `${context.serverUrl}/${context.repo.owner}/${context.repo.repo}/actions/runs/${run.id}`;

          // Find associated PR number from the triggering workflow run
          const prs = run.pull_requests;
          if (!prs || prs.length === 0) {
            // Fallback: search for open PR matching the head branch/SHA
            const { data: pulls } = await github.rest.pulls.list({
              owner: context.repo.owner,
              repo: context.repo.repo,
              state: 'open',
              head: `${run.head_repository.owner.login}:${run.head_branch}`,
            });
            if (pulls.length === 0) {
              console.log('No associated PR found, skipping.');
              return;
            }
            prs.push(pulls[0]);
          }
          const prNumber = prs[0].number;

          // Fetch artifacts from the completed workflow run
          const { data: { artifacts } } = await github.rest.actions.listWorkflowRunArtifacts({
            owner: context.repo.owner,
            repo: context.repo.repo,
            run_id: run.id,
          });

          let rows = '';
          for (const a of artifacts) {
            const dlUrl = `${runUrl}/artifacts/${a.id}`;
            rows += `| ${a.name} | [${a.name}](${dlUrl}) | ${(a.size_in_bytes / 1024).toFixed(0)} KB |\n`;
          }

          if (!rows) {
            rows = `| - | No artifacts found | - |\n`;
          }

          // Check for existing comment to update (upsert pattern)
          const comments = await github.paginate(
            github.rest.issues.listComments,
            {
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: prNumber,
              per_page: 100,
            }
          );
          const marker = '<!-- build-artifacts -->';
          const existing = comments.find(c => c.body.includes(marker));

          const body = [
            marker,
            '### Build Artifacts',
            '',
            '| Platform | Download | Size |',
            '|----------|----------|------|',
            rows.trim(),
            '',
            `> [Full workflow run](${runUrl})`,
            '',
            `<sub>Updated by CI at ${new Date().toISOString()}</sub>`,
          ].join('\n');

          if (existing) {
            await github.rest.issues.updateComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              comment_id: existing.id,
              body,
            });
            console.log(`Updated comment ${existing.id} on PR #${prNumber}`);
          } else {
            await github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: prNumber,
              body,
            });
            console.log(`Created new comment on PR #${prNumber}`);
          }