name: Check for image compression

on:
  workflow_call:

jobs:
  compress:
    name: Compress and make a PR if needed
    runs-on: ubuntu-24.04

    steps:
      - name: Checkout repository
        uses: actions/checkout@v4

      - name: Install optipng
        run: |
          if ! command -v optipng >/dev/null 2>&1; then
            sudo apt-get update && sudo apt-get install -y optipng
          fi

      - name: Get PNG files
        id: get_png_files
        run: |
          png_files=$(mktemp) &&
          {
            if [ "${{ github.event_name }}" = pull_request ] &&
               [ "${{ !github.event.pull_request.draft }}" = true ]; then
              git fetch origin "$GITHUB_BASE_REF:$GITHUB_BASE_REF" &&
              git diff --name-only --diff-filter=AM --no-renames "origin/$GITHUB_BASE_REF" -- '*.png'
            else
              find "$GITHUB_WORKSPACE" -type f -name "*.png" ! -path "$GITHUB_WORKSPACE/.git/*" -print 2> /dev/null || :
            fi
          } > "$png_files" &&
          printf 'png_files=%s\n' "$png_files" >> "$GITHUB_OUTPUT"

      - name: Optimize PNG files
        id: optimize_png
        run: |
          lf="$(printf '\nx')"&&lf=${lf%?}
          png_files=${{ steps.get_png_files.outputs.png_files }}
          trap 'rm -f -- "$png_files"' EXIT INT
          failed_files=""
          while IFS= read -r file; do
            [ -n "$file" ] || continue
            workspace_file=${file#"$GITHUB_WORKSPACE"}
            printf 'Compressing: %s\n' "$workspace_file"
            if ! optipng -o7 -nc -quiet "$file" >/dev/null 2>&1; then
              failed_files="$failed_files$workspace_file$lf"
            fi
          done < "$png_files"

          if [ -n "$failed_files" ]; then
            printf 'failed_files<<EOF\n%sEOF\n' "$failed_files" >> "$GITHUB_OUTPUT"
          fi

      - name: Print files that failed to compress
        if: failure() && steps.optimize_png.outputs.failed_files != ''
        run: |
          printf 'The following files failed to compress:\n%s\n' "${{ steps.optimize_png.outputs.failed_files }}"

      - name: Check for changes
        id: check_changes
        run: |
          if [ -n "$(git status --porcelain)" ]; then
            echo "needs_compression=true"
          else
            echo "needs_compression=false"
          fi >> "$GITHUB_OUTPUT"

      - name: Create Pull Request if Needed
        if: ${{ steps.check_changes.outputs.needs_compression == 'true' && github.event_name == 'pull_request' && !github.event.pull_request.draft }}
        run: |
          git config user.name "GitHub GTNH Actions"
          git config user.email "${{ github.actor_id }}+${{ github.actor }}@users.noreply.github.com" &&
          git switch -c "${FIXED_BRANCH}"
          git commit -am "optimizing images"
          git push --force-with-lease origin "${FIXED_BRANCH}"
          gh pr create \
            --head "${FIXED_BRANCH}" \
            --base "${PR_BRANCH}" \
            --title "Optimising images contained in ${PR_BRANCH} for #${{ github.event.pull_request.number }}" \
            --body "Automatic image compression, applies to PR #${{ github.event.pull_request.number }}" \
            2>&1 | tee pr-message.log || true
          gh pr comment "${{ github.event.pull_request.number }}" -F pr-message.log || true
        shell: bash # ensures set -eo pipefail
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          PR_BRANCH: ${{ github.head_ref }}
          FIXED_BRANCH: ${{ github.head_ref }}-image-compression