add classic, migrating nodes classes

lua/nvim-tree/classic.lua

@@ -0,0 +1,77 @@
+--
+-- classic
+--
+-- Copyright (c) 2014, rxi
+--
+-- This module is free software; you can redistribute it and/or modify it under
+-- the terms of the MIT license. See LICENSE for details.
+--
+
+
+local Object = {}
+Object.__index = Object
+
+
+function Object:new()
+end
+
+
+function Object:extend()
+  local cls = {}
+  for k, v in pairs(self) do
+    if k:find("__") == 1 then
+      cls[k] = v
+    end
+  end
+  cls.__index = cls
+  cls.super = self
+  setmetatable(cls, self)
+  return cls
+end
+
+
+function Object:implement(...)
+  for _, cls in pairs({...}) do
+    for k, v in pairs(cls) do
+      if self[k] == nil and type(v) == "function" then
+        self[k] = v
+      end
+    end
+  end
+end
+
+
+function Object:is(T)
+  local mt = getmetatable(self)
+  while mt do
+    if mt == T then
+      return true
+    end
+    mt = getmetatable(mt)
+  end
+  return false
+end
+
+
+---Return object if it is an instance of class, otherwise nil
+---@generic T
+---@param cls T
+---@return T|nil
+function Object:as(cls)
+  return self:is(cls) and self or nil
+end
+
+
+function Object:__tostring()
+  return "Object"
+end
+
+
+function Object:__call(...)
+  local obj = setmetatable({}, self)
+  obj:new(...)
+  return obj
+end
+
+
+return Object