README.md

@@ -3,13 +3,12 @@
 ## Building the executable
 
 ```
-$ nix build
+$ $(nix-build utoy.nix)/bin/utoy
 ```
 
 ## Building the Docker image
 
 ```
-# TODO
 $ docker load < $(nix-build nix/docker-image.nix)
 ```
 
@@ -18,12 +17,5 @@ $ docker load < $(nix-build nix/docker-image.nix)
 Includes Stack, `haskell-language-server`, `gen-hie` etc.
 
 ```
-nix develop
+$ nix-shell
-```
-
-## Running Stack and GHC
-
-```
-nix run .#stack
-nix run .#ghc
 ```

flake.lock

@@ -1,27 +0,0 @@
-{
-  "nodes": {
-    "nixpkgs": {
-      "locked": {
-        "lastModified": 1680273054,
-        "narHash": "sha256-Bs6/5LpvYp379qVqGt9mXxxx9GSE789k3oFc+OAL07M=",
-        "owner": "nixos",
-        "repo": "nixpkgs",
-        "rev": "3364b5b117f65fe1ce65a3cdd5612a078a3b31e3",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nixos",
-        "ref": "nixpkgs-unstable",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
-    "root": {
-      "inputs": {
-        "nixpkgs": "nixpkgs"
-      }
-    }
-  },
-  "root": "root",
-  "version": 7
-}

flake.nix

@@ -1,76 +0,0 @@
-{
-  description = "Unicode toy";
-
-  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
-
-  outputs = { self, nixpkgs }:
-    let
-      overlay = import ./nix/overlay.nix;
-      settings = import ./nix/settings.nix;
-      haskellDeps = import ./nix/haskell-deps.nix;
-
-      pkgs = nixpkgs.legacyPackages.x86_64-linux.extend overlay;
-      haskellPackages = pkgs.haskell.packages."${settings.ghc}";
-
-      ghc = haskellPackages.ghcWithPackages haskellDeps;
-      stack = pkgs.stdenv.mkDerivation {
-        name = "stack";
-        dontUnpack = true;
-        dontConfigure = true;
-        dontBuild = true;
-        nativeBuildInputs = [ pkgs.makeWrapper ];
-        installPhase = ''
-          makeWrapper ${pkgs.stack}/bin/stack $out/bin/stack \
-            --prefix PATH : ${ghc}/bin \
-            --add-flags '--no-nix --system-ghc --no-install-ghc'
-        '';
-      };
-      utoy' =
-        { mkDerivation }:
-        mkDerivation {
-          version = "0.5";
-          pname = "utoy";
-          license = pkgs.lib.licenses.mit;
-          src =
-            let
-              buildFiles = [
-                ./LICENSE
-                ./utoy.cabal
-                ./Setup.hs
-                ./app
-                ./src
-                ./static
-                ./test
-              ];
-            in
-              pkgs.lib.sources.cleanSourceWith {
-                src = ./.;
-                filter = path: _type: pkgs.lib.any (prefix: pkgs.lib.hasPrefix (toString prefix) path) buildFiles;
-              };
-
-          libraryHaskellDepends = haskellDeps haskellPackages;
-        };
-        utoy = pkgs.haskell.lib.justStaticExecutables (haskellPackages.callPackage utoy' {});
-    in {
-      packages.x86_64-linux = {
-        inherit ghc;
-        inherit stack;
-        inherit utoy;
-
-        default = utoy;
-      };
-
-      devShells.x86_64-linux.default = pkgs.mkShell {
-        packages = [
-          stack
-          ghc
-
-          haskellPackages.haskell-language-server
-          haskellPackages.implicit-hie
-        ];
-        shellHook = ''
-          PS1+="(utoy) ";
-        '';
-      };
-  };
-}

nix/pkgs.nix

@@ -1,4 +1,6 @@
+{ overlays ? [] }:
 let
+  sources = import ./sources.nix;
   settings = import ./settings.nix;
 
   overlay = final: prev: {
@@ -20,4 +22,4 @@ let
     unicode-data-names = pkgs.haskell.lib.markUnbroken prev.unicode-data-names;
   };
 in
-  overlay
+  import sources.nixpkgs { overlays = overlays ++ [overlay]; }

nix/settings.nix

@@ -1,5 +1,5 @@
 {
   # GHC version to use with Nix.
   # Should match the one in stack.yaml.
-  ghc = "ghc944";
+  ghc = "ghc943";
 }

nix/sources.json

@@ -0,0 +1,26 @@
+{
+    "niv": {
+        "branch": "master",
+        "description": "Easy dependency management for Nix projects",
+        "homepage": "https://github.com/nmattia/niv",
+        "owner": "nmattia",
+        "repo": "niv",
+        "rev": "689d0e5539eddd0b0f566aee7bb18629eee7df74",
+        "sha256": "1rld3lk42l6b01f2gcrhq8qm9vry1awmfl29zmpiqda9dy89vbx0",
+        "type": "tarball",
+        "url": "https://github.com/nmattia/niv/archive/689d0e5539eddd0b0f566aee7bb18629eee7df74.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nixpkgs": {
+        "branch": "nixpkgs-unstable",
+        "description": "Nix Packages collection",
+        "homepage": "",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "9952d6bc395f5841262b006fbace8dd7e143b634",
+        "sha256": "0kvpf63dda6nzbqd2kyr99qh1av89mva26xykp3zb4diyicp7yji",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs/archive/9952d6bc395f5841262b006fbace8dd7e143b634.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    }
+}

nix/sources.nix

@@ -0,0 +1,194 @@
+# This file has been generated by Niv.
+
+let
+
+  #
+  # The fetchers. fetch_<type> fetches specs of type <type>.
+  #
+
+  fetch_file = pkgs: name: spec:
+    let
+      name' = sanitizeName name + "-src";
+    in
+      if spec.builtin or true then
+        builtins_fetchurl { inherit (spec) url sha256; name = name'; }
+      else
+        pkgs.fetchurl { inherit (spec) url sha256; name = name'; };
+
+  fetch_tarball = pkgs: name: spec:
+    let
+      name' = sanitizeName name + "-src";
+    in
+      if spec.builtin or true then
+        builtins_fetchTarball { name = name'; inherit (spec) url sha256; }
+      else
+        pkgs.fetchzip { name = name'; inherit (spec) url sha256; };
+
+  fetch_git = name: spec:
+    let
+      ref =
+        if spec ? ref then spec.ref else
+          if spec ? branch then "refs/heads/${spec.branch}" else
+            if spec ? tag then "refs/tags/${spec.tag}" else
+              abort "In git source '${name}': Please specify `ref`, `tag` or `branch`!";
+      submodules = if spec ? submodules then spec.submodules else false;
+      submoduleArg =
+        let
+          nixSupportsSubmodules = builtins.compareVersions builtins.nixVersion "2.4" >= 0;
+          emptyArgWithWarning =
+            if submodules == true
+            then
+              builtins.trace
+                (
+                  "The niv input \"${name}\" uses submodules "
+                  + "but your nix's (${builtins.nixVersion}) builtins.fetchGit "
+                  + "does not support them"
+                )
+                {}
+            else {};
+        in
+          if nixSupportsSubmodules
+          then { inherit submodules; }
+          else emptyArgWithWarning;
+    in
+      builtins.fetchGit
+        ({ url = spec.repo; inherit (spec) rev; inherit ref; } // submoduleArg);
+
+  fetch_local = spec: spec.path;
+
+  fetch_builtin-tarball = name: throw
+    ''[${name}] The niv type "builtin-tarball" is deprecated. You should instead use `builtin = true`.
+        $ niv modify ${name} -a type=tarball -a builtin=true'';
+
+  fetch_builtin-url = name: throw
+    ''[${name}] The niv type "builtin-url" will soon be deprecated. You should instead use `builtin = true`.
+        $ niv modify ${name} -a type=file -a builtin=true'';
+
+  #
+  # Various helpers
+  #
+
+  # https://github.com/NixOS/nixpkgs/pull/83241/files#diff-c6f540a4f3bfa4b0e8b6bafd4cd54e8bR695
+  sanitizeName = name:
+    (
+      concatMapStrings (s: if builtins.isList s then "-" else s)
+        (
+          builtins.split "[^[:alnum:]+._?=-]+"
+            ((x: builtins.elemAt (builtins.match "\\.*(.*)" x) 0) name)
+        )
+    );
+
+  # The set of packages used when specs are fetched using non-builtins.
+  mkPkgs = sources: system:
+    let
+      sourcesNixpkgs =
+        import (builtins_fetchTarball { inherit (sources.nixpkgs) url sha256; }) { inherit system; };
+      hasNixpkgsPath = builtins.any (x: x.prefix == "nixpkgs") builtins.nixPath;
+      hasThisAsNixpkgsPath = <nixpkgs> == ./.;
+    in
+      if builtins.hasAttr "nixpkgs" sources
+      then sourcesNixpkgs
+      else if hasNixpkgsPath && ! hasThisAsNixpkgsPath then
+        import <nixpkgs> {}
+      else
+        abort
+          ''
+            Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
+            add a package called "nixpkgs" to your sources.json.
+          '';
+
+  # The actual fetching function.
+  fetch = pkgs: name: spec:
+
+    if ! builtins.hasAttr "type" spec then
+      abort "ERROR: niv spec ${name} does not have a 'type' attribute"
+    else if spec.type == "file" then fetch_file pkgs name spec
+    else if spec.type == "tarball" then fetch_tarball pkgs name spec
+    else if spec.type == "git" then fetch_git name spec
+    else if spec.type == "local" then fetch_local spec
+    else if spec.type == "builtin-tarball" then fetch_builtin-tarball name
+    else if spec.type == "builtin-url" then fetch_builtin-url name
+    else
+      abort "ERROR: niv spec ${name} has unknown type ${builtins.toJSON spec.type}";
+
+  # If the environment variable NIV_OVERRIDE_${name} is set, then use
+  # the path directly as opposed to the fetched source.
+  replace = name: drv:
+    let
+      saneName = stringAsChars (c: if isNull (builtins.match "[a-zA-Z0-9]" c) then "_" else c) name;
+      ersatz = builtins.getEnv "NIV_OVERRIDE_${saneName}";
+    in
+      if ersatz == "" then drv else
+        # this turns the string into an actual Nix path (for both absolute and
+        # relative paths)
+        if builtins.substring 0 1 ersatz == "/" then /. + ersatz else /. + builtins.getEnv "PWD" + "/${ersatz}";
+
+  # Ports of functions for older nix versions
+
+  # a Nix version of mapAttrs if the built-in doesn't exist
+  mapAttrs = builtins.mapAttrs or (
+    f: set: with builtins;
+    listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set))
+  );
+
+  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/lists.nix#L295
+  range = first: last: if first > last then [] else builtins.genList (n: first + n) (last - first + 1);
+
+  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L257
+  stringToCharacters = s: map (p: builtins.substring p 1 s) (range 0 (builtins.stringLength s - 1));
+
+  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L269
+  stringAsChars = f: s: concatStrings (map f (stringToCharacters s));
+  concatMapStrings = f: list: concatStrings (map f list);
+  concatStrings = builtins.concatStringsSep "";
+
+  # https://github.com/NixOS/nixpkgs/blob/8a9f58a375c401b96da862d969f66429def1d118/lib/attrsets.nix#L331
+  optionalAttrs = cond: as: if cond then as else {};
+
+  # fetchTarball version that is compatible between all the versions of Nix
+  builtins_fetchTarball = { url, name ? null, sha256 }@attrs:
+    let
+      inherit (builtins) lessThan nixVersion fetchTarball;
+    in
+      if lessThan nixVersion "1.12" then
+        fetchTarball ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
+      else
+        fetchTarball attrs;
+
+  # fetchurl version that is compatible between all the versions of Nix
+  builtins_fetchurl = { url, name ? null, sha256 }@attrs:
+    let
+      inherit (builtins) lessThan nixVersion fetchurl;
+    in
+      if lessThan nixVersion "1.12" then
+        fetchurl ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
+      else
+        fetchurl attrs;
+
+  # Create the final "sources" from the config
+  mkSources = config:
+    mapAttrs (
+      name: spec:
+        if builtins.hasAttr "outPath" spec
+        then abort
+          "The values in sources.json should not have an 'outPath' attribute"
+        else
+          spec // { outPath = replace name (fetch config.pkgs name spec); }
+    ) config.sources;
+
+  # The "config" used by the fetchers
+  mkConfig =
+    { sourcesFile ? if builtins.pathExists ./sources.json then ./sources.json else null
+    , sources ? if isNull sourcesFile then {} else builtins.fromJSON (builtins.readFile sourcesFile)
+    , system ? builtins.currentSystem
+    , pkgs ? mkPkgs sources system
+    }: rec {
+      # The sources, i.e. the attribute set of spec name to spec
+      inherit sources;
+
+      # The "pkgs" (evaluated nixpkgs) to use for e.g. non-builtin fetchers
+      inherit pkgs;
+    };
+
+in
+mkSources (mkConfig {}) // { __functor = _: settings: mkSources (mkConfig settings); }

shell.nix

@@ -0,0 +1,21 @@
+{ pkgs ? import ./nix/pkgs.nix {} }:
+let
+  haskellDeps = import ./nix/haskell-deps.nix;
+  settings = import ./nix/settings.nix;
+  haskellPackages = pkgs.haskell.packages."${settings.ghc}";
+
+  tools = with pkgs; [
+    # nix tools
+    niv
+    nix-tree
+
+    # haskell tools
+    stack
+    (haskellPackages.ghcWithPackages haskellDeps)
+    haskellPackages.haskell-language-server
+    haskellPackages.implicit-hie
+  ];
+in
+  pkgs.mkShellNoCC {
+    nativeBuildInputs = tools;
+  }

stack-shell.nix

@@ -0,0 +1,10 @@
+{}:
+let
+  pkgs = import ./nix/pkgs.nix {};
+  haskellDeps = import ./nix/haskell-deps.nix;
+  settings = import ./nix/settings.nix;
+in
+  pkgs.haskell.lib.buildStackProject {
+    name = "utoy";
+    ghc = pkgs.haskell.packages."${settings.ghc}".ghcWithPackages haskellDeps;
+  }

stack.yaml

@@ -1,4 +1,9 @@
-# You can get a working environment using nix develop.
+resolver: ghc-9.4.3
-resolver: ghc-9.4.4
+# GHC is managed through Nix
+install-ghc: false
 packages:
 - .
+nix:
+  enable: true
+  shell-file: stack-shell.nix
+  path: ["nixpkgs=./nix/pkgs.nix"]

utoy.nix

@@ -0,0 +1,35 @@
+let
+  pkgs = import ./nix/pkgs.nix {};
+  settings = import ./nix/settings.nix;
+  haskellDeps = import ./nix/haskell-deps.nix;
+
+  haskellPackages = pkgs.haskell.packages."${settings.ghc}";
+
+  utoy =
+    { mkDerivation }:
+    mkDerivation {
+      version = "0.5";
+      pname = "utoy";
+      license = pkgs.lib.licenses.mit;
+      src =
+        let
+          buildFiles = [
+            ./LICENSE
+            ./utoy.cabal
+            ./Setup.hs
+            ./app
+            ./src
+            ./static
+            ./test
+          ];
+        in
+          pkgs.lib.sources.cleanSourceWith {
+            src = ./.;
+            filter = path: _type: pkgs.lib.any (prefix: pkgs.lib.hasPrefix (toString prefix) path) buildFiles;
+          };
+
+      libraryHaskellDepends = haskellDeps haskellPackages;
+    };
+in
+  pkgs.haskell.lib.justStaticExecutables
+    (haskellPackages.callPackage utoy {})