Try rewrite code to improve service configuration

lib.nix

@@ -0,0 +1,55 @@
+{ blog-source, blog-source-localized, pkgs }:
+
+with pkgs;
+
+let
+  requiredPackages = import ./required-packages.nix { inherit pkgs nodejs; };
+  website = settings: stdenv.mkDerivation {
+    name = "blog-static";
+    version = settings.source.rev;
+    src = settings.source;
+    ssl = settings.ssl;
+    urlSub =
+      let
+        regexEscape = lib.escape [ "/" "(" ")" "[" "]" "+" "*" "\\" ];
+      in
+        if (settings ? replaceUrl)
+        then (with settings.replaceUrl; "s/${regexEscape from}/${regexEscape to}/g")
+        else "";
+    publicPath = settings.path;
+    extraFlags = if settings.drafts then " -D " else "";
+    builder = ./build/builder.sh;
+    converter = ./build/convert.rb;
+    server = ./build/katexserver.js;
+    buildInputs = [
+      hugo nodejs
+      requiredPackages."katex-0.11.1"
+      requiredPackages.express
+      requiredPackages.body-parser
+      (ruby.withPackages (ps: [ ps.nokogiri ]))
+    ];
+  };
+  wrapHost = ssl: host: (if ssl then "https" else "http") + "//${host}";
+in
+  lib = {
+    english = settings: website {
+      inherit (settings) drafts;
+      ssl = settings.ssl or false;
+      source = blog-source;
+      path = ".";
+      replaceUrl = {
+        from = "https://danilafe.com";
+        to = wrapHost settings.ssl settings.host;
+      };
+    };
+    russian = settings: website {
+      inherit (settings) drafts;
+      ssl = settings.ssl or false;
+      source = blog-source-localized;
+      path = "ru";
+      replaceUrl = {
+        from = "https://ru.danilafe.com";
+        to = wrapHost settings.ssl settings.host;
+      };
+    };
+  };