chore: initial commit

lib/flake/default.nix

@@ -0,0 +1,130 @@
+{ core-inputs
+, user-inputs
+, snowfall-lib
+}:
+
+let
+  inherit (core-inputs.nixpkgs.lib) assertMsg fold filterAttrs const;
+in
+rec {
+  flake = rec {
+    # Remove the `self` attribute from an attribute set.
+    # Type: Attrs -> Attrs
+    # Usage: without-self { self = {}; x = true; }
+    #   result: { x = true; }
+    without-self = flake-inputs: builtins.removeAttrs flake-inputs [ "self" ];
+
+    # Remove the `src` attribute from an attribute set.
+    # Type: Attrs -> Attrs
+    # Usage: without-src { src = ./.; x = true; }
+    #   result: { x = true; }
+    without-src = flake-inputs: builtins.removeAttrs flake-inputs [ "src" ];
+
+    # Remove the `src` and `self` attributes from an attribute set.
+    # Type: Attrs -> Attrs
+    # Usage: without-snowfall-inputs { self = {}; src = ./.; x = true; }
+    #   result: { x = true; }
+    without-snowfall-inputs = snowfall-lib.fp.compose without-self without-src;
+
+    # Remove Snowfall-specific attributes so the rest can be safely
+    # passed to flake-utils-plus.
+    # Type: Attrs -> Attrs
+    # Usage: without-snowfall-options { src = ./.; x = true; }
+    #   result: { x = true; }
+    without-snowfall-options = flake-options:
+      builtins.removeAttrs
+        flake-options
+        [
+          "systems"
+          "modules"
+          "overlays"
+          "packages"
+          "outputs-builder"
+          "outputsBuilder"
+          "packagesPrefix"
+          "hosts"
+          "channels-config"
+          "templates"
+        ];
+
+    # Transform an attribute set of inputs into an attribute set where
+    # the values are the inputs' `lib` attribute. Entries without a `lib`
+    # attribute are removed.
+    # Type: Attrs -> Attrs
+    # Usage: get-lib { x = nixpkgs; y = {}; }
+    #   result: { x = nixpkgs.lib; }
+    get-libs = attrs:
+      let
+        # @PERF(jakehamilton): Replace filter+map with a fold.
+        attrs-with-libs = filterAttrs
+          (name: value: builtins.isAttrs (value.lib or null))
+          attrs;
+        libs =
+          builtins.mapAttrs (name: input: input.lib) attrs-with-libs;
+      in
+      libs;
+
+  };
+
+  mkFlake = full-flake-options:
+    let
+      custom-flake-options = flake.without-snowfall-options full-flake-options;
+      systems = snowfall-lib.system.create-systems (full-flake-options.systems or {});
+      hosts = snowfall-lib.attrs.merge-shallow [ (full-flake-options.systems.hosts or {}) systems ];
+      templates = snowfall-lib.template.create-templates {
+        overrides = (full-flake-options.templates or {});
+      };
+      modules = snowfall-lib.module.create-modules {
+        overrides = (full-flake-options.modules or {});
+      };
+
+      outputs-builder = channels:
+        let
+          user-outputs-builder =
+            full-flake-options.outputs-builder
+            or full-flake-options.outputsBuilder
+            or (const {});
+          user-outputs = user-outputs-builder channels;
+          packages = snowfall-lib.package.create-packages {
+            inherit channels;
+            overrides = (full-flake-options.packages or {}) // (user-outputs.packages or {});
+          };
+          shells = snowfall-lib.shell.create-shells {
+            inherit channels;
+            overrides = (full-flake-options.shells or {}) // (user-outputs.devShells or {});
+          };
+
+          outputs = {
+            inherit packages;
+
+            devShells = shells;
+          };
+        in
+        snowfall-lib.attrs.merge-deep [ user-outputs outputs ];
+
+      flake-options = custom-flake-options // {
+        inherit hosts templates;
+        inherit (user-inputs) self;
+
+        lib = snowfall-lib.internal.system-lib;
+        inputs = snowfall-lib.flake.without-src user-inputs;
+
+        nixosModules = modules;
+
+        channelsConfig = full-flake-options.channels-config or {};
+
+        overlays = core-inputs.flake-utils-plus.lib.exportOverlays ({
+          inherit (user-inputs.self) pkgs;
+          inputs = user-inputs;
+        });
+
+        channels.nixpkgs.overlaysBuilder = snowfall-lib.overlay.create-overlays {
+          overlay-package-namespace = full-flake-options.overlay-package-namespace or null;
+          extra-overlays = full-flake-options.overlays or [];
+        };
+
+        outputsBuilder = outputs-builder;
+      };
+    in
+    core-inputs.flake-utils-plus.lib.mkFlake flake-options;
+}