feat(class): basic class implementation

wip, feedback appreciated.

imports/class/shared.lua

@@ -0,0 +1,105 @@
+lib.print.warn('ox_lib\'s class module is experimental and may break without warning.')
+
+lib.class = {}
+
+-- Fields added to the "private" field on a class will not be msgpacked.
+-- Use setters/getters when working with these values.
+local private_mt = {
+    __ext = 0,
+    __pack = function() return '' end,
+}
+
+local function newClass(self, obj)
+    if obj.private then
+        setmetatable(obj.private, private_mt)
+    end
+
+    setmetatable(obj, self)
+
+    if self.init then obj:init() end
+
+    return obj
+end
+
+---@param self table
+---@param metamethod string
+---@param value any
+local function setMetamethod(self, metamethod, value)
+    local mt = getmetatable(self)
+
+    if not mt then return error('no metatable') end
+    if not metamethod:match('^__%w+$') then return error('invalid metamethod') end
+
+    rawset(getmetatable(self), metamethod, value)
+end
+
+---@param name? string
+function lib.class.new(name)
+    local data = {}
+    local class = {
+        __index = data,
+        __newindex = data,
+        __name = name or nil,
+        new = newClass,
+        setMetamethod = setMetamethod,
+    }
+
+    return setmetatable(class, class)
+end
+
+return lib.class
+
+--[[
+---@type table<string, Fruit>
+local fruits = {}
+
+---@class Fruit
+---@field private new fun(self: self, obj): self
+---@field private setMetamethod fun(self: self, metamethod: string, value: any)
+---@field private init fun(self: self)
+---@field private private table
+---@field name string
+---@field colour string
+local Fruit = lib.class.new('Fruit')
+
+function Fruit:init()
+    print(('Created an %s %s'):format(self:getColour(), self:getName()))
+    fruits[self.name] = self
+end
+
+function Fruit:remove()
+    print('Removed', self:getName(), self)
+    fruits[self.name] = nil
+end
+
+Fruit:setMetamethod('__gc', function(self) print('ran __gc', self.name) end)
+
+function Fruit:getName() return self.name end
+function Fruit:getColour() return self.colour end
+function Fruit:getSeeds() return self.private.seeds end
+
+CreateThread(function()
+    local apple = Fruit:new({
+        name = 'apple',
+        colour = 'red'
+    })
+
+    local orange = Fruit:new({
+        name = 'orange',
+        colour = 'orange',
+        private = {
+            seeds = 7
+        }
+    })
+
+    if apple:getColour() == 'red' then
+        print('the apple is red')
+    end
+
+    print(('the orange contains %d seeds'):format(orange:getSeeds()))
+
+    for _, fruit in pairs(fruits) do
+        fruit:remove()
+    end
+end)
+]]