link-checker-pr.yml

name: Link Checker for Pull requests

on: pull_request

jobs:
  changedFiles:
    runs-on: ubuntu-latest
    outputs:
      files: ${{ steps.changed-markdown-files.outputs.all_changed_files }}

    steps:
      - uses: actions/checkout@v4

      - name: Get changed markdown files
        id: changed-markdown-files
        uses: tj-actions/changed-files@v46
        with:
          files: |
            **/*.md
          matrix: true


  linkChecker:
    runs-on: ubuntu-latest
    needs: changedFiles
    if: ${{ needs.changedFiles.outputs.files != '' && toJSON(fromJSON(needs.changedFiles.outputs.files)) != '[]' }}

    strategy:
      matrix:
        file: ${{ fromJSON(needs.changedFiles.outputs.files) }}
      fail-fast: false

    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 2

      - name: Download Lychee
        run: |
          wget https://github.com/lycheeverse/lychee/releases/download/lychee-v0.19.1/lychee-x86_64-unknown-linux-gnu.tar.gz
          tar xzf lychee-x86_64-unknown-linux-gnu.tar.gz

      - name: Check added lines in file for broken links
        run: |
          BASE_SHA="${{ github.event.pull_request.base.sha }}"
          HEAD_SHA="${{ github.event.pull_request.head.sha }}"

          echo "Checking links in changed lines of: ${{ matrix.file }}"

          # Extract raw added lines from diff
          DIFF=$(git diff -U0 "$BASE_SHA" "$HEAD_SHA" -- ${{ matrix.file }} | \
            grep -v "+++" | grep "^+" | cut -c 2-)

          if [ -z "$DIFF" ]; then
            echo "No added lines at all. Skipping."
            exit 0
          fi

          # Extract only actual URLs from added lines
          LINK_LINES=$(echo "$DIFF" | grep -Eo '(https?://[^ )\]}]+|www\.[^ )\]}]+)' || true)

          if [ -z "$LINK_LINES" ]; then
            echo "Added lines contain no URLs. Skipping link checking."
            exit 0
          fi

          echo "Running Lychee on extracted links:"
          echo "$LINK_LINES"

          echo "$LINK_LINES" | \
            ./lychee \
              --fallback-extensions=md \
              --exclude-all-private \
              --exclude support.posit.co \
              --exclude www.intel.com \
              --exclude reddit.com \
              --exclude jsfiddle.net \
              --exclude 'file://'