repo: removed shell.nix and moved to nix flakes

.bazelignore

@@ -0,0 +1,3 @@
+# While using flakes, bazel might pickup the sources used 
+# as flake input stored in direnv and lead to a broken build.
+.direnv

README.md

@@ -10,7 +10,12 @@ It has been tested with the Artix-7 [counter example][counter-example], where it
 
 ## Usage
 
-First, install [Bazel][bazel] and ensure you have a basic C/C++ toolchain set up. Then run:
+First, install [Bazel][bazel] and ensure you have a basic C/C++ toolchain set up.
+
+> [!NOTE]
+> If you are using Nix or NixOS, ensure you have [flakes enabled][enable-flakes] and enter the development shell via `nix develop`.
+
+Then run:
 
 ```
 bazel run -c opt //fpga:fpga-as -- --prjxray_db_path=/some/path/prjxray-db/artix7 --part=xc7a35tcsg324-1 < /some/path.fasm > output.bit
@@ -66,3 +71,4 @@ Using this metadata, you can search the segbits database for the specific featur
 [bazel]: https://bazel.build/
 [counter-example]: https://github.com/chipsalliance/f4pga-examples/blob/13f11197b33dae1cde3bf146f317d63f0134eacf/xc7/counter_test/counter.v
 [open-fpga-loader]: https://github.com/trabucayre/openFPGALoader
+[enable-flakes]: https://nixos.wiki/wiki/Flakes#Enable_flakes_permanently_in_NixOS

flake.nix

@@ -0,0 +1,57 @@
+{
+  description = "fpga-assembler";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+        };
+      in {
+        devShells.default =
+          let
+            bazel = pkgs.bazel_7;
+
+            # There is too much volatility between even micro-versions of
+            # newer clang-format. Use slightly older version for now.
+            clang_for_formatting = pkgs.llvmPackages_17.clang-tools;
+
+            # clang tidy: use latest.
+            clang_for_tidy = pkgs.llvmPackages_18.clang-tools;
+          in with pkgs; pkgs.mkShell{
+            packages = with pkgs; [
+              git
+              bazel
+              jdk
+              bash
+              gdb
+
+              # For clang-tidy and clang-format.
+              clang_for_formatting
+              clang_for_tidy
+
+              # For buildifier, buildozer.
+              bazel-buildtools
+              bant
+
+              # Profiling and sanitizers.
+              linuxPackages_latest.perf
+              pprof
+              perf_data_converter
+              valgrind
+
+              # FPGA utils.
+              openfpgaloader
+            ];
+
+            CLANG_TIDY="${clang_for_tidy}/bin/clang-tidy";
+            CLANG_FORMAT="${clang_for_formatting}/bin/clang-format";
+          };
+      }
+    );
+}