generate-cover-image.yml

name: Generate Cover Images

on:
  pull_request:
    types: [opened, synchronize]
    paths:
      - 'src/content/blog/**/index.md'

permissions:
  contents: write
  pull-requests: write

jobs:
  generate-covers:
    name: Generate Missing Cover Images
    runs-on: ubuntu-latest
    steps:
      - name: Checkout PR branch
        uses: actions/checkout@v4
        with:
          ref: ${{ github.head_ref }}
          fetch-depth: 0
          token: ${{ secrets.GITHUB_TOKEN }}

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '20'

      - name: Install dependencies
        run: npm ci

      - name: Find blog posts needing covers
        id: find-posts
        run: |
          # Get list of changed files in this PR
          CHANGED_FILES=$(git diff --name-only origin/${{ github.base_ref }}...HEAD)

          # Find blog post directories with changes but no cover.png
          POSTS_NEEDING_COVERS=""

          for file in $CHANGED_FILES; do
            # Check if it's a blog post index.md
            if [[ "$file" =~ ^src/content/blog/[0-9]+/.+/index\.md$ ]]; then
              POST_DIR=$(dirname "$file")
              COVER_PATH="$POST_DIR/cover.png"

              # Check if cover.png already exists
              if [ ! -f "$COVER_PATH" ]; then
                POSTS_NEEDING_COVERS="$POSTS_NEEDING_COVERS $POST_DIR"
                echo "Post needs cover: $POST_DIR"
              else
                echo "Post already has cover: $POST_DIR"
              fi
            fi
          done

          # Trim leading space and output
          POSTS_NEEDING_COVERS=$(echo "$POSTS_NEEDING_COVERS" | xargs)
          echo "posts=$POSTS_NEEDING_COVERS" >> $GITHUB_OUTPUT

          if [ -z "$POSTS_NEEDING_COVERS" ]; then
            echo "No posts need cover images"
            echo "has_posts=false" >> $GITHUB_OUTPUT
          else
            echo "has_posts=true" >> $GITHUB_OUTPUT
          fi

      - name: Generate cover images
        if: steps.find-posts.outputs.has_posts == 'true'
        run: |
          for post_dir in ${{ steps.find-posts.outputs.posts }}; do
            echo "Generating cover for: $post_dir"
            node scripts/generate-cover.js "$post_dir"
          done

      - name: Commit and push cover images
        if: steps.find-posts.outputs.has_posts == 'true'
        run: |
          git config user.name "github-actions[bot]"
          git config user.email "github-actions[bot]@users.noreply.github.com"

          # Add only the generated cover images
          for post_dir in ${{ steps.find-posts.outputs.posts }}; do
            git add "$post_dir/cover.png"
          done

          # Check if there are changes to commit
          if git diff --staged --quiet; then
            echo "No new cover images to commit"
            echo "committed=false" >> $GITHUB_OUTPUT
          else
            git commit -m "ci(blog): generate cover images for new posts [skip ci]"
            git push
            echo "committed=true" >> $GITHUB_OUTPUT
          fi

      - name: Comment on PR with cover images
        if: steps.find-posts.outputs.has_posts == 'true'
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          # Get the commit SHA after push
          COMMIT_SHA=$(git rev-parse HEAD)

          # Build comment body with all generated covers
          COMMENT="## 🖼️ Generated Cover Images\n\n"

          for post_dir in ${{ steps.find-posts.outputs.posts }}; do
            # Extract post title from directory name
            POST_SLUG=$(basename "$post_dir")
            POST_YEAR=$(basename $(dirname "$post_dir"))

            # Build raw GitHub URL for the image
            IMAGE_URL="https://raw.githubusercontent.com/${{ github.repository }}/${COMMIT_SHA}/${post_dir}/cover.png"

            COMMENT="${COMMENT}### ${POST_YEAR}/${POST_SLUG}\n\n"
            COMMENT="${COMMENT}![Cover Image](${IMAGE_URL})\n\n"
          done

          COMMENT="${COMMENT}---\n*If you'd like a different style, delete the cover image and push again, or generate one locally with \`npm run cover\`.*"

          # Post comment to PR
          echo -e "$COMMENT" | gh pr comment ${{ github.event.pull_request.number }} --body-file -