refactor: Move nix outside of .config dir

Technically not a config but a compose file, so I think it's better to
have outside of `.config` dir

nix/overlays/darwin/brew.nix

@@ -0,0 +1,105 @@
+# Modified version of brew-nix/casks.nix
+#
+# REF: https://github.com/BatteredBunny/brew-nix/blob/9dfab294afea5029922bbc59a10ae487c7318d59/casks.nix
+{ system, mac-version ? "ventura", nixpkgs, brew-api, ... }:
+let
+  pkgs = import nixpkgs {
+    inherit system;
+  };
+
+  hasBinary = cask: pkgs.lib.hasAttr "binary" (getArtifacts cask);
+  hasApp = cask: pkgs.lib.hasAttr "app" (getArtifacts cask);
+  hasPkg = cask: pkgs.lib.hasAttr "pkg" (getArtifacts cask);
+
+  getName = cask: builtins.elemAt cask.name 0;
+
+  getBinary = cask: builtins.elemAt (getArtifacts cask).binary 0;
+  getApp = cask: builtins.elemAt (getArtifacts cask).app 0;
+  getArtifacts = cask: pkgs.lib.mergeAttrsList cask.artifacts;
+
+  getUrl = cask: (cask.variations.${mac-version} or cask).url;
+  getHash = cask: (cask.variations.${mac-version} or cask).sha256;  # TODO: convert it to SRI
+
+  caskToDerivation = cask: pkgs.stdenv.mkDerivation rec {
+    pname = cask.token;
+    version = cask.version;
+
+    src = pkgs.fetchurl {
+      url = (getUrl cask);
+      sha256 = pkgs.lib.optionalString ((getHash cask) != "no_check") (getHash cask);
+    };
+
+    nativeBuildInputs = with pkgs; [
+      undmg
+      unzip
+      gzip
+      _7zz
+      makeWrapper
+    ] ++ pkgs.lib.optional (hasPkg cask) (with pkgs; [
+      xar
+      cpio
+    ]);
+
+    unpackPhase =
+      if (hasPkg cask) then ''
+        xar -xf $src
+        for pkg in $(cat Distribution | grep -oE "#.+\.pkg" | sed -e "s/^#//" -e "s/$/\/Payload/"); do
+          zcat $pkg | cpio -i
+        done
+      '' else if (hasApp cask) then ''
+        undmg $src || 7zz x -snld $src
+      '' else if (hasBinary cask) then ''
+        if [ "$(file --mime-type -b "$src")" == "application/gzip" ]; then
+          gunzip $src -c > ${getBinary cask}
+        elif [ "$(file --mime-type -b "$src")" == "application/x-mach-binary" ]; then
+          cp $src ${getBinary cask}
+        fi
+      '' else "";
+
+    sourceRoot = pkgs.lib.optionalString (hasApp cask) (getApp cask);
+
+    installPhase =
+      if (hasPkg cask) then ''
+        mkdir -p $out/Applications
+        cp -R Applications/* $out/Applications/
+
+        if [ -d "Resources" ]; then
+          mkdir -p $out/Resources
+          cp -R Resources/* $out/Resources/
+        fi
+
+        if [ -d "Library" ]; then
+          mkdir -p $out/Library
+          cp -R Library/* $out/Library/
+        fi
+      '' else if (hasApp cask) then ''
+        mkdir -p "$out/Applications/${sourceRoot}"
+        cp -R . "$out/Applications/${sourceRoot}"
+
+        if [[ -e "$out/Applications/${sourceRoot}/Contents/MacOS/${getName cask}" ]]; then
+          makeWrapper "$out/Applications/${sourceRoot}/Contents/MacOS/${getName cask}" $out/bin/${cask.token}
+        elif [[ -e "$out/Applications/${sourceRoot}/Contents/MacOS/${pkgs.lib.removeSuffix ".app" sourceRoot}" ]]; then
+          makeWrapper "$out/Applications/${sourceRoot}/Contents/MacOS/${pkgs.lib.removeSuffix ".app" sourceRoot}" $out/bin/${cask.token}
+        fi
+      '' else if (hasBinary cask && !hasApp cask) then ''
+        mkdir -p $out/bin
+        cp -R ./* $out/bin
+      '' else "";
+
+    meta = {
+      homepage = cask.homepage;
+      description = cask.desc;
+      platforms = pkgs.lib.platforms.darwin;
+      mainProgram = if (hasBinary cask && !hasApp cask) then (getBinary cask) else (cask.token);
+    };
+  };
+
+  casks = builtins.fromJSON (builtins.readFile (brew-api + "/cask.json"));
+in final: prev: {
+  casks = builtins.listToAttrs (builtins.map
+    (cask: {
+      name = cask.token;
+      value = caskToDerivation cask;
+    })
+    casks);
+}

nix/overlays/darwin/heliport.nix

@@ -0,0 +1,28 @@
+# REF: https://github.com/bandithedoge/nixpkgs-firefox-darwin/blob/ceaca2359e5371ccef3f92a36baf7c438b354afb/overlay.nix
+final: prev:
+
+let
+  mkApp = import ../../lib/darwin/mkApp.nix;
+  version = "1.5.0";
+in {
+  heliport = mkApp {
+    inherit (final) stdenv undmg _7zz;
+
+    pname = "HeliPort";
+    appFileName = "HeliPort.app";
+    inherit version;
+
+    src = final.fetchurl {
+      url = "https://github.com/OpenIntelWireless/HeliPort/releases/download/v${version}/HeliPort.dmg";
+      sha256 = "49cbe7abea742a3c662a836f14c05b79b3e6e6577c897b57101f5bd0a086eec8";
+    };
+
+    meta = with final.lib; {
+      description = "Intel WiFi Client for itlwm";
+      homepage = "https://github.com/OpenIntelWireless/HeliPort";
+      license = licenses.bsd3;
+      platforms = platforms.darwin;
+      sourceProvenance = with sourceTypes; [ binaryNativeCode ];
+    };
+  };
+}

nix/overlays/darwin/vesktop.nix

@@ -0,0 +1,28 @@
+# REF: https://github.com/bandithedoge/nixpkgs-firefox-darwin/blob/ceaca2359e5371ccef3f92a36baf7c438b354afb/overlay.nix
+final: prev:
+
+let
+  mkApp = import ../../lib/darwin/mkApp.nix;
+  version = "1.5.3";
+in {
+  vesktop = mkApp {
+    inherit (final) stdenv undmg _7zz;
+
+    pname = "Vesktop";
+    appFileName = "Vesktop*.app";
+    inherit version;
+
+    src = final.fetchurl {
+      url = "https://github.com/Vencord/Vesktop/releases/download/v${version}/Vesktop-${version}-universal.dmg";
+      hash = "sha256-ceOUNHSOaEqCbzkM64RtUu0Yhrq4tThcXZTDd+OsEXI";
+    };
+
+    meta = with final.lib; {
+      description = "An alternate client for Discord with Vencord built-in";
+      homepage = "https://github.com/Vencord/Vesktop";
+      license = licenses.gpl3Only;
+      platforms = platforms.darwin;
+      sourceProvenance = with sourceTypes; [ binaryNativeCode ];
+    };
+  };
+}