enforce-image-size.yml

name: Enforce image size on PR

on:
  pull_request:
    types: [opened, synchronize, reopened]

permissions:
  contents: read
  pull-requests: write   # needed to comment on PR

jobs:
  check-images:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Install ffmpeg (includes ffprobe)
        run: |
          sudo apt-get update
          sudo apt-get install -y ffmpeg

      - name: Detect oversized images (>1280px)
        id: scan
        shell: bash
        run: |
          set -euo pipefail
          MAX=1280

          git fetch --no-tags --prune origin "${GITHUB_BASE_REF}:${GITHUB_BASE_REF}" || true

          mapfile -d '' files < <(
            git diff --name-only --diff-filter=AM -z "origin/${GITHUB_BASE_REF}...HEAD" -- \
              '*.png' '*.jpg' '*.jpeg' '*.PNG' '*.JPG' '*.JPEG' || true
          )

          oversized=""
          for f in "${files[@]}"; do
            [[ -f "$f" ]] || continue

            read -r w h < <(
              ffprobe -v error -select_streams v:0 -show_entries stream=width,height \
                -of default=noprint_wrappers=1:nokey=1 "$f" | tr '\n' ' '
            )

            if [[ "${w:-0}" -gt "${MAX}" || "${h:-0}" -gt "${MAX}" ]]; then
              oversized+="${f} (${w}x${h})\n"
            fi
          done

          if [[ -n "$oversized" ]]; then
            {
              echo "oversized<<EOF"
              echo -e "$oversized"
              echo "EOF"
            } >> "$GITHUB_OUTPUT"
            echo "has_oversized=true" >> "$GITHUB_OUTPUT"
          else
            echo "has_oversized=false" >> "$GITHUB_OUTPUT"
          fi

      - name: Comment on PR with fix instructions
        if: steps.scan.outputs.has_oversized == 'true'
        uses: actions/github-script@v7
        with:
          script: |
            const marker = "<!-- image-size-check -->";
            const max = 1280;
            const oversized = `${{ steps.scan.outputs.oversized }}`.trim();

            const body =
              `${marker}\n` +
              `👋 Thanks for the PR! A quick heads-up: some images in this PR exceed **${max}px** (width or height).\n\n` +
              `**Oversized images:**\n` +
              "```\n" + oversized + "\n```\n\n" +
              `**How to fix (in your fork):**\n` +
              `1) Pull latest changes\n` +
              `2) Run:\n` +
              "```bash\n" +
              "chmod +x scripts/resize-images.sh\n" +
              "./scripts/resize-images.sh\n" +
              "```\n" +
              `3) Commit + push the updated images\n\n` +
              `This check will turn green automatically after you push the resize commit. 🙌`;

            const { owner, repo } = context.repo;
            const issue_number = context.payload.pull_request.number;

            // Find existing bot comment and update it to avoid spam
            const comments = await github.paginate(github.rest.issues.listComments, {
              owner, repo, issue_number, per_page: 100
            });

            const existing = comments.find(c => c.user?.type === "Bot" && c.body?.includes(marker));

            if (existing) {
              await github.rest.issues.updateComment({
                owner, repo, comment_id: existing.id, body
              });
            } else {
              await github.rest.issues.createComment({
                owner, repo, issue_number, body
              });
            }

      - name: Fail if oversized images found
        if: steps.scan.outputs.has_oversized == 'true'
        run: |
          echo "Oversized images detected. See PR comment for instructions."
          exit 1