proof-links.yml

name: Proof Links
on: [pull_request, workflow_dispatch]

env:
  HUGO_VERSION: 0.147.8
  LYCHEE_RELEASE: "lychee-v0.15.1-x86_64-unknown-linux-gnu.tar.gz"
  LYCHEE_VERSION_TAG: "v0.15.1"

jobs:
  proof-links:
    runs-on: ubuntu-latest
    concurrency:
      group: ${{ github.workflow }}-${{ github.ref }}
    steps:
      - name: Checkout
        uses: actions/checkout@v4

      - name: Setup Hugo
        uses: peaceiris/actions-hugo@v3
        with:
          hugo-version: ${{ env.HUGO_VERSION }}
          extended: true

      - name: Setup Node
        uses: actions/setup-node@v3
        with:
          node-version: '20'

      - name: Cache dependencies
        uses: actions/cache@v4
        with:
          path: ~/.npm
          key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}
          restore-keys: |
            ${{ runner.os }}-node-

      - name: Cache Hugo Modules
        uses: actions/cache@v4
        with:
          path: /tmp/hugo_cache
          key: ${{ runner.os }}-hugomod-${{ hashFiles('**/go.sum') }}
          restore-keys: |
            ${{ runner.os }}-hugomod-

      - name: Install Dependencies
        working-directory: site
        run: npm ci

      - name: Build Spine
        working-directory: site
        run: hugo -e development

      # Cache Lychee results to avoid hitting rate limits.
      - name: Cache Lychee results
        uses: actions/cache@v4
        with:
          path: .lycheecache
          key: cache-lychee-results

      - name: Cache Lychee executable
        id: cache-lychee
        uses: actions/cache@v4
        with:
          path: lychee
          key: ${{ runner.os }}-${{ env.LYCHEE_RELEASE }}

      # We use Lychee directly instead of a GitHub Action because it
      # must have access the local Hugo server, which is not visible
      # from the Docker-based action.
      - name: Download Lychee executable
        uses: robinraju/release-downloader@v1.7
        if: steps.cache-lychee.outputs.cache-hit != 'true'
        with:
          repository: "lycheeverse/lychee"
          tag: ${{ env.LYCHEE_VERSION_TAG }}
          fileName: ${{ env.LYCHEE_RELEASE }}

      - name: Extract Lychee executable
        if: steps.cache-lychee.outputs.cache-hit != 'true'
        run: |
          mkdir -p lychee &&
          tar -xf ${{ env.LYCHEE_RELEASE }} -C lychee

      # 1. In the generated HTML, some inner links will have absolute URLs and
      #    the link checker will attempt to fetch them. That's why we need
      #    a server. Sadly, link checkers have no settings to address this.
      # 2. Output redirection is necessary for nohup in GitHub Actions.
      # 3. Sleep makes sure the server is up before the next step.
      - name: Start Hugo server
        working-directory: site
        run: |
          nohup hugo server \
          --environment development \
          > nohup.out 2> nohup.err < /dev/null & 
          sleep 5

      - name: Check if the cache file exists
        run: |
          if [ -f ".lycheecache" ]; then
            echo "Lychee cache exists."
          else
            echo "No lychee cache file."
          fi

      - name: Check links
        run: |
          ./lychee/lychee --config lychee.toml --timeout 60 \
          --base http://localhost:1313/ \
          'site/public/**/*.html'