feat: rxi/classic object abstraction (#134)

lua/plenary/class.lua

@@ -0,0 +1,81 @@
+---@brief [[
+---classic
+---
+---Copyright (c) 2014, rxi
+---@brief ]]
+
+---@class Object
+local Object = {}
+Object.__index = Object
+
+---Does nothing.
+---You have to implement this yourself for extra functionality when initializing
+---@param self Object
+function Object:new()
+end
+
+---Create a new class/object by extending the base Object class.
+---The extended object will have a field called `super` that will access the super class.
+---@param self Object
+---@return Object
+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
+
+---Implement a mixin onto this Object.
+---@param self Object
+---@param nil ...
+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
+
+---Checks if the object is an instance
+---This will start with the lowest class and loop over all the superclasses.
+---@param self Object
+---@param T Object
+---@return boolean
+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
+
+---The default tostring implementation for an object.
+---You can override this to provide a different tostring.
+---@param self Object
+---@return string
+function Object:__tostring()
+  return "Object"
+end
+
+---You can call the class the initialize it without using `Object:new`.
+---@param self Object
+---@param nil ...
+---@return Object
+function Object:__call(...)
+  local obj = setmetatable({}, self)
+  obj:new(...)
+  return obj
+end
+
+return Object