flake.nix

{
  description = "A Nix-flake-based Rust development environment";

  inputs = {
    nixpkgs.url = "https://flakehub.com/f/NixOS/nixpkgs/0.1.*.tar.gz";
    rust-overlay = {
      url = "github:oxalica/rust-overlay";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = {
    self,
    nixpkgs,
    rust-overlay,
  }: let
    overlays = [
      rust-overlay.overlays.default
      (final: prev: {
        rustToolchain = let
          rust = prev.rust-bin;
        in
          if builtins.pathExists ./rust-toolchain.toml
          then rust.fromRustupToolchainFile ./rust-toolchain.toml
          else if builtins.pathExists ./rust-toolchain
          then rust.fromRustupToolchainFile ./rust-toolchain
          else
            rust.stable.latest.default.override {
              extensions = ["rust-src" "rustfmt"];
            };
      })
    ];
    supportedSystems = ["x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin"];
    forEachSupportedSystem = f:
      nixpkgs.lib.genAttrs supportedSystems (system:
        f {
          pkgs = import nixpkgs {inherit overlays system;};
        });
  in {
    devShells = forEachSupportedSystem ({pkgs}: {
      default = pkgs.mkShell {
        packages = with pkgs; [
          rustToolchain
          rustup
          openssl
          pkg-config
          cargo-deny
          cargo-edit
          cargo-watch
          rust-analyzer
          cmake

          graphviz
        ];
      };
    });
  };
}