Add Nix flake for Compact compiler

.envrc

@@ -0,0 +1,4 @@
+# Enter a `nix develop` shell if installed
+if command -v nix >/dev/null 2>&1; then
+  use flake
+fi

.gitignore

@@ -58,4 +58,8 @@ jspm_packages/
 *.sln
 
 # Compact
-managed/
+managed/
+
+# nix
+.direnv
+.nix-bin

flake.nix

@@ -0,0 +1,66 @@
+{
+  description = "Nix flake that provides the Compact compiler per system";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";
+    nixpkgs-unstable.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  };
+
+  outputs = inputs:
+    let
+      supportedSystems = [
+        "x86_64-linux"
+        "x86_64-darwin"
+        "aarch64-darwin"
+      ];
+      forEachSupportedSystem = f:
+        inputs.nixpkgs.lib.genAttrs supportedSystems (
+          system:
+            f {
+              pkgs = import inputs.nixpkgs { inherit system; };
+              pkgsUnstable = import inputs."nixpkgs-unstable" { inherit system; };
+              inherit system;
+            }
+        );
+    in
+    {
+      devShells = forEachSupportedSystem ({ pkgs, pkgsUnstable, system }:
+        let
+          # Compact toolchain version to use
+          compactVersion = "0.24.0";
+
+          installScript = pkgs.writeShellScript "setup-compact" ''
+            set -euo pipefail
+
+            # Use project-local compact installation in .nix-bin
+            COMPACT_DIR="$PWD/.nix-bin"
+            export COMPACT_INSTALL_DIR="$COMPACT_DIR"
+
+            # Install compact CLI tool if not present
+            if [ ! -x "$COMPACT_DIR/compact" ]; then
+              echo "Installing compact developer tools to $COMPACT_DIR..."
+              curl --proto '=https' --tlsv1.2 -LsSf https://github.com/midnightntwrk/compact/releases/latest/download/compact-installer.sh | COMPACT_NO_MODIFY_PATH=1 sh
+            fi
+
+            # Update to specific toolchain version
+            "$COMPACT_DIR/compact" update ${compactVersion}
+
+            # Patch shebang for NixOS (only needed on NixOS)
+            if [ ! -f "/bin/bash" ]; then
+              find "$COMPACT_DIR/.compact/versions/${compactVersion}" -name "compactc" -type f -exec sed -i '1s|^#!/bin/bash|#!/usr/bin/env bash|' {} \; 2>/dev/null || true
+            fi
+          '';
+        in
+        {
+          default = pkgs.mkShell {
+            packages = [ pkgs.curl pkgs.unzip pkgsUnstable.nodejs pkgs.yarn ];
+            shellHook = ''
+              ${installScript}
+              export PATH="$PWD/.nix-bin:$PATH"
+            '';
+          };
+        }
+      );
+    };
+}
+