Add basic haskell-nix setup

.gitignore

@@ -0,0 +1,4 @@
+.direnv
+result*
+dist-newstyle
+.pre-commit-config.yaml

flake.nix

@@ -0,0 +1,61 @@
+{
+  nixConfig.allow-import-from-derivation = true;
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
+    parts.url = "github:hercules-ci/flake-parts";
+    haskell-flake.url = "github:srid/haskell-flake";
+    pre-commit-hooks.url = "github:cachix/pre-commit-hooks.nix";
+    devshell.url = "github:numtide/devshell";
+    devshell.inputs.nixpkgs.follows = "nixpkgs";
+  };
+  outputs = inputs:
+    inputs.parts.lib.mkFlake {inherit inputs;} {
+      systems = ["x86_64-linux"];
+      imports = [
+        inputs.devshell.flakeModule
+        inputs.haskell-flake.flakeModule
+        inputs.pre-commit-hooks.flakeModule
+      ];
+
+      perSystem = {
+        config,
+        # pkgs,
+        # lib,
+        ...
+      }: {
+        devshells.default = {
+          devshell = {
+            packagesFrom = [config.devShells.ghc96];
+            packages = [];
+            startup = {
+              pre-commit.text = config.pre-commit.installationScript;
+            };
+          };
+        };
+        pre-commit = {
+          check.enable = true;
+          settings.hooks = {
+            cabal-fmt.enable = true;
+            hlint.enable = true;
+
+            alejandra.enable = true;
+            statix.enable = true;
+            deadnix.enable = true;
+          };
+        };
+        haskellProjects.ghc96 = {
+          # packages = {};
+          # settings = {};
+          projectRoot = ./message-index;
+          # devShell.mkShellArgs = {
+          #   packages = [
+          #     # pkgs.zlib.dev
+          #     # pkgs.haskellPackages.zlib
+          #     # pkgs.haskellPackages.zlib_0_7_1_0.dev
+          #   ];
+          #   # shellHook = config.pre-commit.installationScript;
+          # };
+        };
+      };
+    };
+}