{
  description = "Robossembler Development Environments on Nix";
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs?ref=master";
    flake-utils.follows = "ros-flake/flake-utils";
    ros-flake.url = "github:lopsided98/nix-ros-overlay?ref=develop";
    gazebo = {
      url = "github:movefasta/gazebo-sim-overlay";
      inputs.flake-utils.follows = "ros-flake/flake-utils";
      inputs.nixpkgs.follows = "ros-flake/nixpkgs";

      # Transitive inputs "not in registry" https://github.com/NixOS/nix/issues/5790
      # inputs.nixgl.inputs.nixpkgs.follows = "ros-flake/nixpkgs";
      # inputs.nixgl.inputs.flake-utils.follows = "ros-flake/flake-utils";
    };
  };

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

          # single source for Robossembler Framework packages
          rbsFrameworkSrc = pkgs.fetchgit {
            url = "https://gitlab.com/robossembler/framework";
            hash = "sha256-K6vnCQn129TWiMEKe81eBx/1H6PaIriCnkHGRwL8fg0=";
            rev = "e8bb59124d56c5aee0180b4c7d5c7bfeec9cb1ea";
          };

          pkgs = import nixpkgs { inherit system; overlays = [ overlay gazebo.overlays.default ]; };

          overlay = final: prev: {
            # -- PLACEHOLDER for overlay
            # freecad = prev.freecad.overrideAttrs
            #   (old: { cmakeFlags = old.cmakeFlags ++ [ "-DBUILD_GUI=OFF" ]; });
            # cmakeFlag -BUILD_GUI=OFF for build without gui
            pythonPackagesExtensions = prev.pythonPackagesExtensions ++ [
              (
                python-final: python-prev: {
                 iopath = python-prev.iopath.overridePythonAttrs (oldAttrs: {
                    version = "unstable";
                    src = pkgs.fetchFromGitHub {
                      owner = "facebookresearch";
                      repo = "iopath";
                      rev = "9dcb63a46447556460fdb65c21aa6d094a7a788c";
                      hash = "sha256-X1LTOfbIAMy6gToNYS0JpeJpHi0jHPsEjrnCq2c9U0E=";
                    };
                  });
                }
              )
            ];
          };

          # overrided packages and attributes for nix-ros-overlay
          humble-overrided = ros.humble.overrideScope (final: prev: {
            # remove after update github:lopsided98/nixpkgs/nix-ros for https://github.com/NixOS/nixpkgs/pull/224099
            behaviortree-cpp-v3 = prev.behaviortree-cpp-v3.overrideAttrs (old: { 
              propagatedBuildInputs = old.propagatedBuildInputs ++ [ pkgs.zeromq ];
            });
            moveit-core = prev.moveit-core.overrideAttrs (old: { 
              propagatedBuildInputs = old.propagatedBuildInputs ++ [ prev.tf2-kdl ];
            });
            moveit-kinematics = prev.moveit-kinematics.overrideAttrs (old: { 
              propagatedBuildInputs = old.propagatedBuildInputs ++ [ final.moveit-ros-planning ];
            });
          });
          
          # robossembler custom packages; defined here for share between devShells and packages
          cg_preferences = pkgs.fetchgit {
            url = "https://gitflic.ru/project/brothermechanic/cg_preferences.git";
            sha256 = "sha256-/mNNjvrhIxSZVv1/LSJ7+c/dXH3E0Orh5Zr0oVPLquY=";
          };
          rs_logo = pkgs.fetchgit {
            url = "https://gitlab.com/robossembler/logo.git";
            rev = "0a0235cd154a59b711e87456206ccd7ba69a7e4e";
            sha256 = "sha256-/QsgKdtDHNymsTEmhIzSrOKNUqqkXl8coy+5LwIEkas=";
            fetchLFS = true;
          };
          blender' = pkgs.blender.override {
            cudaSupport = true;
            spaceNavSupport = false;
            waylandSupport = false;
          };
          blender = blender'.overrideAttrs (old: {
            optix = pkgs.fetchzip {
              # url taken from the archlinux blender PKGBUILD
              url = "https://developer.download.nvidia.com/redist/optix/v7.4/OptiX-7.4.0-Include.zip";
              sha256 = "sha256-ca08XetwaUYC9foeP5bff9kcDfuFgEzopvjspn2s8RY=";
            };
            patches = old.patches ++ [ "${cg_preferences}/patches/cg-defaults.patch" ];
            buildInputs = old.buildInputs ++ [ pkgs.imath pkgs.git ];
            postPatch = old.postPatch + ''
              cp ${cg_preferences}/share/00_cg_preferences_service.py scripts/startup/
              cp ${cg_preferences}/share/startup.blend release/datafiles/
              cp ${rs_logo}/raster/robossembler_1024x512_roboty-rossii.png  release/datafiles/splash.png
            '';
            env.NIX_CFLAGS_COMPILE = old.env.NIX_CFLAGS_COMPILE + " -I${pkgs.imath}/include/Imath";
            postInstall = old.postInstall + ''
              cp -r ${cg_preferences}/cg_preferences $out/share/blender/${
                pkgs.lib.versions.majorMinor pkgs.blender.version
              }/scripts/addons/
            '';
          });
          bpy = blender.overrideAttrs (old: {
            pname = "bpy";
            src = pkgs.fetchurl {
              url = "https://download.blender.org/source/${old.pname}-${old.version}.tar.xz";
              hash = "sha256-3AAtguPDQMk4VcZoRzDQGAG2aaKbHMa3XuuZC6aecj8=";
            };
            cmakeFlags = old.cmakeFlags ++ [
              "-DWITH_PYTHON_INSTALL=OFF"
              "-DWITH_AUDASPACE=OFF"
              "-DWITH_PYTHON_MODULE=ON"
              "-DWITH_MEM_JEMALLOC=OFF"
              "-DWITH_INSTALL_PORTABLE=ON"
            ];
            postInstall = ''
              mkdir -p $out/nix-support
              mkdir -p $out/lib/python${pkgs.python3.pythonVersion}/site-packages
              ln -s $out/bpy $out/lib/python${pkgs.python3.pythonVersion}/site-packages/bpy
              echo ${pkgs.python3} >> $out/nix-support/propagated-build-inputs
            '';
          });
          bpy-wheel = pkgs.python3Packages.callPackage ./pkgs/development/python-modules/bpy-wheel { };
          pysdf = pkgs.python3Packages.callPackage ./pkgs/development/python-modules/pysdf { };
          pytorch3d = pkgs.python3Packages.callPackage ./pkgs/development/python-modules/pytorch3d { };
          mayo = pkgs.libsForQt5.callPackage ./pkgs/misc/mayo { };
          fstl = pkgs.libsForQt5.callPackage ./pkgs/misc/fstl { };
          open3d = pkgs.python3Packages.callPackage ./pkgs/development/python-modules/open3d {  };
          unified-planning = pkgs.python3Packages.callPackage ./pkgs/development/python-modules/unified-planning { };
          blenderproc = pkgs.python3Packages.callPackage ./blenderproc.nix { };
          test-script = pkgs.python3Packages.callPackage ./pkgs/development/python-modules/test-script { };
          webdataset = pkgs.python3Packages.callPackage ./pkgs/development/python-modules/webdataset { };
          ansitable = pkgs.python3Packages.callPackage ./pkgs/development/python-modules/ansitable { };
          megapose6d = pkgs.python3Packages.callPackage ./pkgs/development/python-modules/megapose6d { inherit webdataset; };
          spatialmath = pkgs.python3Packages.callPackage ./pkgs/development/python-modules/spatialmath { inherit ansitable; };
          rcg-pipeline = pkgs.python3Packages.callPackage ./pkgs/development/python-modules/rcg-pipeline { bpy = bpy-lib; inherit rbsFrameworkSrc; };
          rbs-workbench = pkgs.python3Packages.callPackage ./pkgs/development/python-modules/freecad.robossembler { inherit freecad-lib; inherit rbsFrameworkSrc; };
          freecad-lib = pkgs.python3Packages.toPythonModule (pkgs.callPackage ./pkgs/misc/freecad-lib { });
          bpy-lib = pkgs.python3Packages.toPythonModule bpy;
          cad-gen = 
          let
            cad_export_script = pkgs.writers.writePython3 "cad_export_script.py"
            { libraries = [ rbs-workbench ]; }
            ''
            import FreeCAD as App
            import freecad.robossembler.utils.freecad_exporters as rbs
            import sys

            path = sys.argv[4]
            print(path)
            doc = App.openDocument(path)
            rbs.publish_project_database(doc)
            App.closeDocument(doc.Name)
            '';
          in
          pkgs.writeShellScriptBin "cad-gen"
            ''
            export PYTHONPATH="${rbs-workbench}/${pkgs.python3.sitePackages}"
            ${pkgs.freecad}/bin/freecadcmd ${cad_export_script} -- --pass $1
            '';
          cg-gen = pkgs.writers.writePython3Bin "cg-gen"
            { libraries = [ rcg-pipeline ]; }
            ''
            from rcg_pipeline import rcg_full_pipeline
            import sys
            rcg_full_pipeline(sys.argv[1])
            '';
        in
        {
          inherit pkgs;

          rlib = import ./. { 
            inherit (pkgs.stdenv) mkDerivation;
            inherit (pkgs) lib;
            inherit mayo;
            inherit (pkgs.libsForQt5) wrapQtAppsHook;
          };

          packages = {
            inherit unified-planning test-script cad-gen cg-gen blender bpy;
          };

          devShells.ci = pkgs.mkShell { buildInputs = [ pkgs.jq ]; };

          devShells.gazebo = gazebo.devShells.${system}.default;

          devShells.ros = 
            pkgs.mkShell {
              buildInputs = (with humble-overrided; [
                ros2run
                rmw-fastrtps-dynamic-cpp
                urdf
                ament-pep257
                ament-lint-auto
                xacro
                ament-cmake
                rclcpp-action
                tf2
                action-msgs
                ament-copyright
                pythonPackages.pytest
                rosidl-default-generators
                behaviortree-cpp-v3
                geometry-msgs
                rosidl-default-runtime
                rclpy
                std-msgs
                ament-lint-common
                ament-flake8
                tf2-ros
                rclcpp
                moveit-core
                moveit-msgs
                moveit-ros-planning
                moveit-ros-planning-interface
                gazebo-ros2-control
                plansys2-bringup
                image-transport
                cv-bridge
                example-interfaces
              ]) ++ (with pkgs; [ nlohmann_json glog lua5_3_compat gazebo_sim ]);
              RMW_IMPLEMENTATION = "rmw_fastrtps_dynamic_cpp";
            };

          devShells.all = pkgs.mkShell { 
            packages = [ blender fstl mayo ];
          };

          devShells.perception =
            let
              rbs-packages = p: with p; [
                torch
                torchvision
                torchaudio
                detectron2
              ];
            in
            pkgs.mkShell {
              packages = [ (pkgs.python3.withPackages rbs-packages) ];
            };

          devShells.default =
            let
              my-python-packages = p: with p; [ 
                unified-planning
                pybullet
                scipy
                spatialmath
                rcg-pipeline
                rbs-workbench
                ledger
              ];
            in
            pkgs.mkShell {
              packages = with pkgs; [ 
                freecad
                mayo
                bashInteractive
              ] ++ [ (pkgs.python3.withPackages my-python-packages) ];
              buildInputs = [  ];

              # Run when the shell is started up
              shellHook = ''
                ${pkgs.python3}/bin/python --version
              '';
            };
        }
      );

  nixConfig = {
    extra-substituters = [ "https://ros.cachix.org" "https://robossembler.cachix.org" ];
    extra-trusted-public-keys = [ 
      "ros.cachix.org-1:dSyZxI8geDCJrwgvCOHDoAfOm5sV1wCPjBkKL+38Rvo="
      "robossembler.cachix.org-1:56jBJHroRQSGpZFkW8XMquuzQTjAF/XTo6MogmBM7SQ="
    ];
  };
}