feat: introduce nix support

.envrc

@@ -0,0 +1,2 @@
+use flake
+dotenv_if_exists .env

.github/workflows/nix.yml

@@ -0,0 +1,21 @@
+name: nix build
+
+on:
+  - push
+  - pull_request
+jobs:
+  check_nix:
+    name: Check nix build
+    runs-on: ubuntu-latest
+    steps:
+      - name: git checkout
+        uses: actions/checkout@v3
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@main
+        with:
+          extra-conf: system-features = nixos-test benchmark big-parallel kvm
+      - uses: DeterminateSystems/magic-nix-cache-action@main
+      - name: Check Nix flake inputs
+        uses: DeterminateSystems/flake-checker-action@v4
+      - name: Build lib
+        run: nix build -L

.gitignore

@@ -8,3 +8,7 @@ tags
 tags.mtime
 .DS_Store
 TAGS
+
+.env
+.direnv
+result

flake.nix

@@ -0,0 +1,54 @@
+{
+  description = "one-time-password";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+    libsodium-bindings.url = "github:haskell-cryptography/libsodium-bindings";
+  };
+
+  outputs = { self, nixpkgs, flake-utils, ... }@inputs:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs{inherit system;};
+
+        haskellPackages = pkgs.haskellPackages.override {
+          overrides = hself: hsuper: {
+              libsodium-bindings = inputs.libsodium-bindings.packages.${system}.libsodium-bindings;
+              sel = inputs.libsodium-bindings.packages.${system}.sel;
+          };
+        };
+      in
+      rec
+      {
+        packages.one-time-password =
+          haskellPackages.callCabal2nix "one-time-password" ./.
+            {
+              base32 = haskellPackages.base32_0_4;
+              sel = inputs.libsodium-bindings.packages.${system}.sel;
+            };
+
+        defaultPackage = packages.one-time-password;
+
+        devShell =
+          let
+            scripts = pkgs.symlinkJoin {
+              name = "scripts";
+              paths = pkgs.lib.mapAttrsToList pkgs.writeShellScriptBin {
+              };
+            };
+          in
+          pkgs.mkShell {
+            buildInputs = with haskellPackages; [
+              pkgs.libsodium
+              haskell-language-server
+              ghcid
+              cabal-install
+              scripts
+            ];
+            inputsFrom = [
+              self.defaultPackage.${system}.env
+            ];
+          };
+      });
+}