feat: import and configure smartcolumn

modules/ui/smartcolumn/config.nix

@@ -0,0 +1,32 @@
+{
+  pkgs,
+  config,
+  lib,
+  ...
+}:
+with lib;
+with builtins; let
+  cfg = config.vim.ui.smartcolumn;
+in {
+  config = mkIf cfg.enable {
+    vim.startPlugins = [
+      "smartcolumn"
+    ];
+
+    vim.luaConfigRC.smartcolumn = nvim.dag.entryAnywhere ''
+      require("smartcolumn").setup({
+         colorcolumn = "${toString cfg.showColumnAt}",
+         disabled_filetypes = { ${concatStringsSep ", " (map (x: "\"" + x + "\"") cfg.disabledFiletypes)} },
+         -- { "help", "text", "markdown", "NvimTree", "alpha"},
+         custom_colorcolumn = {
+           -- TODO: use cfg.languages.<language>.columnAt when it's fixed to dynamically define per-language length
+           ruby = "120",
+           java = "120",
+           nix = "120",
+           markdown = "80",
+         },
+         scope = "file",
+      })
+    '';
+  };
+}

modules/ui/smartcolumn/default.nix

@@ -0,0 +1,6 @@
+_: {
+  imports = [
+    ./smartcolumn.nix
+    ./config.nix
+  ];
+}

modules/ui/smartcolumn/smartcolumn.nix

@@ -0,0 +1,41 @@
+{
+  config,
+  lib,
+  ...
+}:
+with lib;
+with builtins; let
+  languageOpts = {
+    columnAt = mkOption {
+      type = types.nullOr types.int;
+      default = 80;
+    };
+  };
+in {
+  options.vim.ui.smartcolumn = {
+    enable = mkEnableOption "Enable smartcolumn line length indicator";
+
+    showColumnAt = mkOption {
+      type = types.nullOr types.int;
+      default = 120;
+      description = "The position at which the column will be displayed. Set to null to disable";
+    };
+
+    disabledFiletypes = mkOption {
+      type = types.listOf types.str;
+      default = ["help" "text" "markdown" "NvimTree" "alpha"];
+      description = "The filetypes smartcolumn will be disabled for.";
+    };
+
+    /*
+    languages = mkOption {
+      default = {};
+      description = "Language specific configuration.";
+      type = with types;
+        attrsOf (submodule {
+          options = attrsOf (submodule langOptions);
+        });
+    };
+    */
+  };
+}