new-shapes/flake.nix

{
  description = "new-shapes - Java Swing shape editor";

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

  outputs = { self, nixpkgs }:
    let
      # JDK 16 (project target) is non-LTS and unavailable in nixpkgs.
      # JDK 17 (LTS) is fully backward-compatible with --source 16 --target 16.
      javaVersion = 17;

      supportedSystems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];

      forEachSystem = f:
        nixpkgs.lib.genAttrs supportedSystems (system: f {
          pkgs = import nixpkgs {
            inherit system;
            overlays = [ self.overlays.default ];
          };
        });
    in
    {
      overlays.default = final: prev:
        let
          jdk = prev."jdk${toString javaVersion}";
        in
        {
          inherit jdk;
          # Override Maven to use the same JDK version
          maven = prev.maven.override { jdk_headless = jdk; };
        };

      devShells = forEachSystem ({ pkgs }: {
        default = pkgs.mkShell {
          packages = with pkgs; [
            jdk
            maven
          ];

          shellHook = ''
            echo "new-shapes dev shell"
            echo "  Java: $(java -version 2>&1 | head -1)"
            echo "  Maven: $(mvn -version 2>&1 | head -1)"
          '';
        };
      });
    };
}