{
  description = "HdM Slides - Marp presentation builder with tools";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};

        # QR code generator script
        qr-gen = pkgs.writeShellScriptBin "qr" ''
          if [ -z "$1" ]; then
            echo "Usage: qr <url> [output.png]"
            echo ""
            echo "Examples:"
            echo "  qr https://example.com"
            echo "  qr https://example.com my-qr.png"
            echo "  qr 'https://librete.ch/hdm/223015b/' slides-qr.png"
            exit 1
          fi

          URL="$1"
          OUTPUT="''${2:-qr-code.png}"

          ${pkgs.qrencode}/bin/qrencode -o "$OUTPUT" -s 10 -m 2 "$URL"
          echo "Generated: $OUTPUT"
        '';

        # QR code for course slides
        qr-slides = pkgs.writeShellScriptBin "qr-slides" ''
          COURSE="''${1:-223015b}"
          OUTPUT="''${2:-build/$COURSE/qr-$COURSE.png}"

          mkdir -p "$(dirname "$OUTPUT")"
          ${pkgs.qrencode}/bin/qrencode -o "$OUTPUT" -s 10 -m 2 "https://librete.ch/hdm/$COURSE/"
          echo "Generated QR for $COURSE: $OUTPUT"
        '';

        # Image optimizer script
        optimize-img = pkgs.writeShellScriptBin "optimize-img" ''
          if [ -z "$1" ]; then
            echo "Usage: optimize-img <image-or-directory> [max-width]"
            echo ""
            echo "Resizes images to max width (default: 1920px)"
            exit 1
          fi

          TARGET="$1"
          MAX_WIDTH="''${2:-1920}"

          if [ -d "$TARGET" ]; then
            for img in "$TARGET"/*.{png,jpg,jpeg,webp} 2>/dev/null; do
              [ -f "$img" ] || continue
              echo "Optimizing: $(basename "$img")"
              ${pkgs.imagemagick}/bin/magick "$img" -resize "''${MAX_WIDTH}x>" -quality 85 "$img"
            done
          elif [ -f "$TARGET" ]; then
            echo "Optimizing: $TARGET"
            ${pkgs.imagemagick}/bin/magick "$TARGET" -resize "''${MAX_WIDTH}x>" -quality 85 "$TARGET"
          else
            echo "Error: $TARGET not found"
            exit 1
          fi
          echo "Done!"
        '';

      in {
        # Development shell with all tools
        devShells.default = pkgs.mkShell {
          buildInputs = with pkgs; [
            nodejs_20
            nodePackages.npm
            qrencode
            imagemagick
            gnumake
          ];

          shellHook = ''
            echo "HdM Slides Development Environment"
            echo ""
            echo "Available commands:"
            echo "  make dev-b     - Start 223015b dev server (port 1312)"
            echo "  make dev-c     - Start 223015c dev server (port 1313)"
            echo "  make build     - Build all courses"
            echo "  qr <url>       - Generate QR code"
            echo "  qr-slides 223015b - Generate QR for course"
            echo "  optimize-img <dir> - Optimize images"
            echo ""
          '';
        };

        # Standalone apps
        packages = {
          qr = qr-gen;
          qr-slides = qr-slides;
          optimize-img = optimize-img;
          default = qr-gen;
        };

        # Direct runnable apps
        apps = {
          qr = {
            type = "app";
            program = "${qr-gen}/bin/qr";
          };
          qr-slides = {
            type = "app";
            program = "${qr-slides}/bin/qr-slides";
          };
          optimize-img = {
            type = "app";
            program = "${optimize-img}/bin/optimize-img";
          };
          default = self.apps.${system}.qr;
        };
      }
    );
}