Nix integration

.gitignore

@@ -8,6 +8,7 @@
 .hpc/
 dist/
 dist-newstyle/
+newdist/
 cabal.sandbox.config
 .ghc.environment.*
 .stack-work

cabal.project

@@ -1,5 +1,7 @@
 -- http://cabal.readthedocs.io/en/latest/nix-local-build-overview.html
-packages: .
--- packages: examples/
+packages:
+  ./
+  benchmarks/
+  examples/
 
 -- tests: True

default.nix

@@ -0,0 +1,28 @@
+{ ghc
+, doCheck ? true
+, configureFlags ? [ ]
+}:
+let
+  haskellNixSrc = builtins.fetchTarball "https://github.com/input-output-hk/haskell.nix/archive/b3df33abbcb736437cb06d5f53a10f6bb271bc51.tar.gz";
+
+  haskellNix = import haskellNixSrc { };
+
+  pkgs = import haskellNix.sources.nixpkgs-unstable haskellNix.nixpkgsArgs;
+
+in {
+  inherit pkgs;
+
+  project = pkgs.haskell-nix.cabalProject {
+    src = pkgs.haskell-nix.haskellLib.cleanGit {
+      name = "cassava";
+      src = ./.;
+    };
+    name = "cassava";
+    compiler-nix-name = ghc;
+    index-state = "2022-09-03T00:00:00Z";
+    modules = [
+      { inherit doCheck configureFlags; }
+    ];
+  };
+
+}

shell.nix

@@ -0,0 +1,33 @@
+{ doCheck ? true
+, ghc ? "ghc902"
+, withHoogle ? true
+, configureFlags ? [ ]
+}:
+let
+  result = import ./default.nix {
+    inherit configureFlags doCheck ghc;
+  };
+
+  inherit (result) pkgs project;
+  hsPkgs = pkgs.haskell.packages.${ghc};
+
+in project.shellFor {
+
+  inherit withHoogle;
+
+  exactDeps = true;
+
+  # We have to add 'criterion' explicitly as it depends on 'cassava' itself,
+  # so it will be dropped from included dependencies and benchmarks build fails.
+  # https://github.com/input-output-hk/haskell.nix/blob/b3df33abbcb736437cb06d5f53a10f6bb271bc51/builder/shell-for.nix#L31-L49)
+  additional = ps: [ps.criterion.components.library];
+
+  buildInputs = [
+    hsPkgs.cabal-install
+    hsPkgs.haskell-language-server
+  ];
+
+  LANG = "en_US.utf8";
+  LC_ALL = "en_US.utf8";
+  LOCALE_ARCHIVE = "${pkgs.glibcLocales}/lib/locale/locale-archive";
+}