feat(plugins): add nvim-ufo

plugins/nvim-ufo.nix

@@ -0,0 +1,47 @@
+# homepage: https://github.com/kevinhwang91/nvim-ufo
+# nixvim doc: https://nix-community.github.io/nixvim/plugins/nvim-ufo/index.html
+_:
+
+{
+  opts = {
+    enable = true;
+
+    preview.mappings = {
+      scrollB = "<c-b>";
+      scrollD = "<c-d>";
+      scrollF = "<c-f>";
+      scrollU = "<c-u>";
+    };
+
+    # https://github.com/AstroNvim/AstroNvim/blob/v4.7.7/lua/astronvim/plugins/nvim-ufo.lua#L28-L44
+    providerSelector = ''
+      function(_, filetype, buftype)
+        local function handleFallbackException(bufnr, err, providerName)
+          if type(err) == "string" and err:match "UfoFallbackException" then
+            return require("ufo").getFolds(bufnr, providerName)
+          else
+            return require("promise").reject(err)
+          end
+        end
+
+        return (filetype == "" or buftype == "nofile") and "indent" -- only use indent until a file is opened
+          or function(bufnr)
+            return require("ufo")
+              .getFolds(bufnr, "lsp")
+              :catch(function(err) return handleFallbackException(bufnr, err, "treesitter") end)
+              :catch(function(err) return handleFallbackException(bufnr, err, "indent") end)
+          end
+      end
+    '';
+  };
+
+  rootOpts.keymaps = [
+    # https://github.com/AstroNvim/AstroNvim/blob/v4.7.7/lua/astronvim/plugins/nvim-ufo.lua#L15
+    {
+      mode = "n";
+      key = "zp";
+      action.__raw = "function() require('ufo').peekFoldedLinesUnderCursor() end";
+      options.desc = "Peek fold";
+    }
+  ];
+}