updated flake.nix to cache

flake.nix

@@ -3,39 +3,57 @@
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    # Ghostty uses 'systems' to be cleaner, we can do similar or stick to a list
+  };
+
+  # This mirrors the Ghostty 'nixConfig' to ensure settings stay local to the project
+  nixConfig = {
+    extra-substituters = ["https://cache.nixos.org"];
+    extra-trusted-public-keys = ["cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="];
   };
 
   outputs = {
     self,
     nixpkgs,
   }: let
-    supportedSystems = ["aarch64-darwin" "x86_64-darwin" "x86_64-linux"];
-    forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
-    pkgsFor = system: import nixpkgs {inherit system;};
-  in {
-    # This allows other flakes to "consume" this library
-    packages = forAllSystems (system: let
-      pkgs = pkgsFor system;
+    supportedSystems = ["aarch64-darwin" "x86_64-darwin" "aarch64-linux" "x86_64-linux"];
+    # A helper to generate outputs for all systems
+    forAllSystems = f: nixpkgs.lib.genAttrs supportedSystems (system: f (import nixpkgs {inherit system;}));
   in {
+    # 1. THE PACKAGE (What you 'pull' into other projects)
+    packages = forAllSystems (pkgs: {
       default = pkgs.stdenv.mkDerivation {
         pname = "image_processor";
         version = "0.1.0";
         src = ./.;
+
         nativeBuildInputs = [pkgs.cmake pkgs.pkg-config];
         buildInputs = [pkgs.libjpeg_turbo];
+
+        # Ensure headers are found in the dev environment
+        propagatedBuildInputs = [pkgs.libjpeg_turbo];
       };
     });
 
-    # This provides the dev environment for the API itself
-    devShells = forAllSystems (system: let
-      pkgs = pkgsFor system;
-    in {
+    # 2. THE DEV SHELL (What 'direnv' uses)
+    devShells = forAllSystems (pkgs: {
       default = pkgs.mkShell {
-        nativeBuildInputs = [pkgs.cmake pkgs.pkg-config];
-        buildInputs = [pkgs.libjpeg_turbo];
+        # Use 'inputsFrom' so the shell always matches the package
+        inputsFrom = [self.packages.${pkgs.system}.default];
+
+        # Add extra dev tools you only want when coding, not building
+        nativeBuildInputs = with pkgs; [
+          gdb
+          pkg-config
+        ];
+
         shellHook = ''
+          # These exports make sure your C compiler finds the Nix-provided libs
           export CPATH="${pkgs.libjpeg_turbo.dev}/include:$CPATH"
-          echo "⚙️ Image Processor API Dev Shell"
+          export LIBRARY_PATH="${pkgs.libjpeg_turbo.out}/lib:$LIBRARY_PATH"
+          export PKG_CONFIG_PATH="${pkgs.libjpeg_turbo.dev}/lib/pkgconfig:$PKG_CONFIG_PATH"
+
+          echo "⚙️ Image Processor API Dev Shell Loaded"
         '';
       };
     });