add nix flake

Author: ahkohd

.envrc

@@ -0,0 +1 @@
+use flake

.gitignore

@@ -2,3 +2,4 @@ target
 node_modules
 dist
 dist-js
+.direnv

flake.lock

@@ -0,0 +1,48 @@
+{
+  inputs = {
+    nixpkgs.url = "nixpkgs";
+    rust-overlay.url = "github:oxalica/rust-overlay";
+  };
+
+  outputs = { self, nixpkgs, rust-overlay }:
+    let
+      overlays = [ rust-overlay.overlays.default ];
+
+      pkgs = import nixpkgs {
+        system = "aarch64-darwin";
+        inherit overlays;
+      };
+      pkgsX86 = import nixpkgs {
+        system = "x86_64-darwin";
+        inherit overlays;
+      };
+
+      rustToolchainExtensions = [ "rust-src" "rust-analyzer" "clippy" ];
+      rustToolchain = pkgs.rust-bin.stable.latest.default.override {
+        targets = [ "aarch64-apple-darwin" ];
+        extensions = rustToolchainExtensions;
+      };
+      rustToolchainX86 = pkgsX86.rust-bin.stable.latest.default.override {
+        targets = [ "x86_64-apple-darwin" ];
+        extensions = rustToolchainExtensions;
+      };
+
+      commonPackages = p: with p; [ bacon ];
+
+    in {
+      devShells = {
+        aarch64-darwin.default = pkgs.mkShellNoCC {
+          packages = [ rustToolchain ] ++ (commonPackages pkgs);
+          shellHook = ''
+            echo "=== 🛠️ DEV SHELL (APPLE SILICON) ==="
+          '';
+        };
+        x86_64-darwin.default = pkgsX86.mkShellNoCC {
+          packages = [ rustToolchainX86 ] ++ (commonPackages pkgsX86);
+          shellHook = ''
+            echo "=== 🛠️ DEV SHELL (APPLE ROSETTA) ==="
+          '';
+        };
+      };
+    };
+}