nix: add flake

flake.nix

@@ -0,0 +1,112 @@
+{
+  description = "A simple calculator";
+
+  inputs = {
+    flake-utils = {
+      type = "github";
+      owner = "numtide";
+      repo = "flake-utils";
+      ref = "master";
+    };
+
+    nixpkgs = {
+      type = "github";
+      owner = "NixOS";
+      repo = "nixpkgs";
+      ref = "nixpkgs-unstable";
+    };
+
+    pre-commit-hooks = {
+      type = "github";
+      owner = "cachix";
+      repo = "pre-commit-hooks.nix";
+      ref = "master";
+      inputs = {
+        flake-utils.follows = "flake-utils";
+        nixpkgs.follows = "nixpkgs";
+      };
+    };
+  };
+
+  outputs =
+    { self
+    , flake-utils
+    , nixpkgs
+    , pre-commit-hooks
+    }:
+    flake-utils.lib.eachDefaultSystem
+      (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [ self.overlay ];
+        };
+      in
+      rec {
+        apps = {
+          dragger = flake-utils.lib.mkApp { drv = packages.dragger; };
+        };
+
+        checks = {
+          pre-commit = pre-commit-hooks.lib.${system}.run {
+            src = self;
+
+            hooks = {
+              clang-format = {
+                enable = true;
+                name = "clang-format";
+                entry = "${pkgs.clang-tools}/bin/clang-format -style=file -i";
+                types = [ "text" "c++" ];
+                language = "system";
+              };
+
+              nixpkgs-fmt = {
+                enable = true;
+              };
+            };
+          };
+        };
+
+        defaultApp = apps.dragger;
+
+        defaultPackage = packages.dragger;
+
+        devShell = pkgs.mkShell {
+          nativeBuildInputs = with pkgs; [ ]
+          ++ defaultPackage.nativeBuildInputs
+          ++ defaultPackage.buildInputs
+          ;
+
+          inherit (checks.pre-commit) shellHook;
+        };
+
+        packages = {
+          inherit (pkgs) dragger;
+        };
+      }) // {
+      overlay = final: prev: {
+        dragger = with final; stdenv.mkDerivation {
+          pname = "dragger";
+          version = "0.1.0";
+
+          src = self;
+
+          buildInputs = [
+            libsForQt5.qt5.qtbase
+          ];
+          nativeBuildInputs = [
+            libsForQt5.qt5.wrapQtAppsHook
+          ];
+
+          configurePhase = ''
+            qmake
+          '';
+
+          installPhase = ''
+            mkdir -p $out/bin
+            cp dragger $out/bin
+          '';
+        };
+      };
+    };
+}