{
  description = "Rust dev env for Meltano toy project";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";
    flake-utils.url = "github:numtide/flake-utils";
  };

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

      python-with-deps = pkgs.python3.withPackages (ps: with ps; [
        pip
        setuptools
        wheel      
        psycopg2   
      ]);

      venvDir = ".venv";

      in {
        devShells.default = pkgs.mkShell {
          packages = [
            pkgs.rustup
            pkgs.cargo
            pkgs.docker
            pkgs.postgresql
            python-with-deps
          ];

          shellHook = ''
            echo "✅ Rust + PostgreSQL dev env ready"

            if [ ! -d ${venvDir} ]; then
              echo "🐍 Creating Python virtualenv..."
              python3 -m venv ${venvDir}
            fi

            source ${venvDir}/bin/activate

            pip install --upgrade pip
            pip install -r requirements.txt

            echo "Python env ready"
          '';
        };
      });
}