chore: add nix flake

flake.nix

@@ -0,0 +1,89 @@
+{
+  outputs = {
+    flake-parts,
+    systems,
+    ...
+  } @ inputs:
+    flake-parts.lib.mkFlake {inherit inputs;} {
+      imports = [
+        inputs.devenv.flakeModule
+        inputs.nix-gitlab-ci.flakeModule
+        inputs.nix-devtools.flakeModule
+        inputs.treefmt.flakeModule
+      ];
+      systems = import systems;
+      perSystem = {
+        lib,
+        pkgs,
+        config,
+        ...
+      }: {
+        treefmt = {
+          projectRootFile = "flake.nix";
+          programs = {
+            alejandra.enable = true;
+            rustfmt.enable = true;
+            taplo.enable = true;
+            mdformat.enable = true;
+          };
+        };
+        devenv.shells.default = {
+          containers = lib.mkForce {};
+          packages = with pkgs; [
+            openssl
+            bacon
+            irust
+          ];
+
+          languages.rust = {
+            enable = true;
+            channel = "stable";
+          };
+
+          # prevent global libs from being used (try making impure a bit purer)
+          enterShell = ''
+            export PKG_CONFIG_PATH="$DEVENV_PROFILE/lib/pkgconfig"
+          '';
+
+          env.RUST_LOG = "trace";
+
+          pre-commit.hooks = {
+            treefmt = {
+              enable = true;
+              packageOverrides.treefmt = config.treefmt.build.wrapper;
+            };
+            clippy.enable = true;
+            convco.enable = true;
+          };
+        };
+      };
+    };
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+
+    flake-parts.url = "github:hercules-ci/flake-parts";
+    systems.url = "github:nix-systems/default";
+    devenv = {
+      url = "github:cachix/devenv";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+    treefmt.url = "github:numtide/treefmt-nix";
+    nix-gitlab-ci.url = "gitlab:TECHNOFAB/nix-gitlab-ci?dir=lib";
+    nix-devtools.url = "gitlab:TECHNOFAB/nix-devtools?dir=lib";
+
+    fenix.url = "github:nix-community/fenix";
+  };
+
+  nixConfig = {
+    extra-substituters = [
+      "https://nix-community.cachix.org"
+      "https://devenv.cachix.org"
+    ];
+
+    extra-trusted-public-keys = [
+      "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+      "devenv.cachix.org-1:w1cLUi8dv3hnoSPGAuibQv+f9TZLr6cv/Hm9XgU50cw="
+    ];
+  };
+}