modules/buffer: add possibility to configure window options

module-list.nix

@@ -7,6 +7,7 @@
   ./modules/vim/keymap.nix
   ./modules/vim/augroup.nix
 
+  ./modules/buffer.nix
   ./modules/filetype.nix
   ./modules/input.nix
   ./modules/plugin.nix

modules/buffer.nix

@@ -0,0 +1,39 @@
+{ config, lib, ... }:
+
+let
+  options = import ./vim/options.nix { inherit lib; };
+
+  bufferOpts = { name, config, ... }: {
+    options = with lib; {
+      filetypes = mkOption {
+        type = types.extCommas;
+        description = "File types for which the buffer is enabled";
+      };
+      opt = options.buffer // options.window;
+    };
+    config = {
+      filetypes = lib.mkDefault name;
+    };
+  };
+
+  mkFiletypeBuffer = name: cfg:
+    lib.nameValuePair
+      "buffer-${name}"
+      {
+        event = "FileType";
+        pattern = cfg.filetypes;
+        callback = with lib; with nix2lua; lambda ["ev"] (lib.flatten [
+          (flip mapAttrsToList cfg.opt (k: v: if v == null then null else set "vim.opt.${k}" v))
+        ]);
+      };
+in
+{
+  options.buffer = lib.mkOption {
+    type = with lib.types; attrsOf (submodule bufferOpts);
+    default = { };
+  };
+
+  config = {
+    vim.augroup = lib.mkIf (config.buffer != {}) (lib.listToAttrs (lib.mapAttrsToList mkFiletypeBuffer config.buffer));
+  };
+}