flake.nix

{
  description = "versioningit";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";

    pyproject-nix = {
      url = "github:pyproject-nix/pyproject.nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    uv2nix = {
      url = "github:pyproject-nix/uv2nix";
      inputs.pyproject-nix.follows = "pyproject-nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    pyproject-build-systems = {
      url = "github:pyproject-nix/build-system-pkgs";
      inputs.pyproject-nix.follows = "pyproject-nix";
      inputs.uv2nix.follows = "uv2nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    systems.url = "github:nix-systems/x86_64-linux";
  };

  # Disclaimer: Uv2nix is new and experimental.
  # Users are expected to be able to contribute fixes.
  #
  # Note that uv2nix is _not_ using Nixpkgs buildPythonPackage.
  # It's using https://pyproject-nix.github.io/pyproject.nix/build.html

  outputs =
    { self, nixpkgs, ... }@inputs:
    let
      inherit (nixpkgs) lib;

      # Load a uv workspace from a workspace root.
      # Uv2nix treats all uv projects as workspace projects.
      workspace = inputs.uv2nix.lib.workspace.loadWorkspace { workspaceRoot = ./.; };

      # Create package overlay from workspace.
      overlay = workspace.mkPyprojectOverlay {
        # Prefer prebuilt binary wheels as a package source.
        # Sdists are less likely to "just work" because of the metadata missing from uv.lock.
        # Binary wheels are more likely to, but may still require overrides for library dependencies.
        sourcePreference = "wheel"; # or sourcePreference = "sdist";
        # Optionally customise PEP 508 environment
        # environ = {
        #   platform_release = "5.10.65";
        # };
      };

      # Extend generated overlay with build fixups
      #
      # Uv2nix can only work with what it has, and uv.lock is missing essential metadata to perform some builds.
      # This is an additional overlay implementing build fixups.
      # See:
      # - https://pyproject-nix.github.io/uv2nix/FAQ.html
      pyprojectOverrides = _final: _prev: {
        # Implement build fixups here.
      };

      eachSystem = nixpkgs.lib.genAttrs (import inputs.systems);
      pkgsFor = eachSystem (system: nixpkgs.legacyPackages.${system});

      # # This example is only using x86_64-linux
      pkgs = nixpkgs.legacyPackages.x86_64-linux;

      # # Use Python 3.13 from nixpkgs
      python = pkgs.python312;

      # Construct package set
      pythonSetFor = eachSystem (
        system:
        let
          # injecting cairosvg from upstream nixpkgs, as it is currently not
          # supported by the uv2nix_hammer project and is still in the todo list.
          # https://pyproject-nix.github.io/pyproject.nix/builders/hacks.html
          pkgs = pkgsFor.${system};
          python = pkgs.python312;
        in
        # Use base package set from pyproject.nix builders
        (pkgs.callPackage inputs.pyproject-nix.build.packages {
          inherit python;
        }).overrideScope
          (
            lib.composeManyExtensions [
              inputs.pyproject-build-systems.overlays.default
              overlay
              pyprojectOverrides
            ]
          )
      );
    in
    {
      packages = eachSystem (
        system:
        let
          pkgs = pkgsFor.${system};
          pythonSet = pythonSetFor.${system};
          # version = should be read from the wrapping venv
          # hardcoding for now
          version = "0.1.0";
        in
        {
          default =
            let
              # Package the virtual environment
              # Enable no optional dependencies for production build.
              venv = pythonSet.mkVirtualEnv "minimal-versioningit-env" workspace.deps.default;
            in
            pkgs.stdenvNoCC.mkDerivation {
              pname = "minimal-versioningit";
              inherit version;
              src = venv;
              meta = {
                license = pkgs.lib.getLicenseFromSpdxId "GPL-3.0";
              };
              buildPhase = ''
                mkdir -p $out/bin
                ln -s $src/bin/hello $out/bin/
              '';
            };
        }
      );
    };
}