class.lua

--[[
class.lua
Copyright 2019-2020 JackMacWindows

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
]]

--[[
    * Define a class with `class "<name>" {<contents>}`
        * This class will be available in the global namespace
    * Set inherited classes by adding `{extends = <class>}` or `{extends = {<classes...>}}` between the name and contents
    * To create a new object, call the class by name: `object = <name>()`
    * The initializer is named __init, and it will be called after creating the object
    * Metamethods are available as class methods or static methods
    * Static properties and methods may be defined in a static block inside the class definition
        * These are not synced to an object's namespace: when `class.a {static {foo = "bar"}}`, `a.foo` is nil
    * The super variable can be used to access methods/properties of the parent class(es)
    * Methods will automatically get self/super variables in their environment
        * Methods should not have a self argument in their definition
        * Do not call methods with the : operator, as self is already handled
    * Multiple inheritance follows the order given in the table
    * Initializer chaining is available by calling the name of the parent class in the initializer
        * `class.a {__init = function(name) self.name = name end}; class.b {__init = function(name, type) a(name); self.type = type end}`
]]
local metamethods = {__add=true, __sub=true, __mul=true, __div=true, __mod=true, __pow=true, __unm=true, __concat=true, __len=true, __eq=true, __lt=true, __le=true, __newindex=true, __call=true, __metatable=true}
local function _wrap_method(obj, func, ...)
    local env = getfenv(func)
    env.self = obj
    env.super = setmetatable({}, {__index = getmetatable(obj).__index})
    setfenv(func, env)
    return func(...)
end
local function defineClass(name, meta, def)
    local c, cmt = {__class = name}, {}
    if def.static then for k,v in pairs(def.static) do if metamethods[k] then cmt[k] = v else c[k] = v end end end
    def.static = nil
    if meta.extends then if meta.extends[1] then cmt.__index = function(self, name) for i,v in ipairs(meta.extends) do if v[name] then return v[name] end end end else cmt.__index = meta.extends end end
    local __init = def.__init
    def.__init = nil
    cmt.__call = function(self, ...)
        local omt, supers = {}, {}
        local obj = setmetatable({__class = name}, omt)
        if meta.extends and not __init then if meta.extends[1] then for i,v in ipairs(meta.extends) do supers[i] = v() end omt.__index = function(self, name) for i,v in ipairs(supers) do if v[name] then return v[name] end end end else omt.__index = meta.extends(...) end end
        for k,v in pairs(def) do if type(v) == "function" then obj[k] = function(...) return _wrap_method(obj, v, ...) end elseif k ~= "__class" then obj[k] = v end if metamethods[k] then omt[k] = obj[k]; obj[k] = nil end end
        if __init then
            local env = getfenv(__init)
            env.self = obj
            env.super = setmetatable({}, {__index = omt.__index})
            if meta.extends then if meta.extends[1] then omt.__index = function(self, name) if #supers < #meta.extends then for i,v in ipairs(meta.extends) do supers[i] = v() end end for i,v in ipairs(supers) do if v[name] then return v[name] end end end for i,v in ipairs(meta.extends) do env[v.__class] = function(...) supers[i] = v(...) end end else omt.__index = function(self, name) omt.__index = meta.extends(); return omt.__index[name] end env[meta.extends.__class] = function(...) omt.__index = meta.extends(...) end end end
            setfenv(__init, env)
            __init(...)
            if meta.extends and meta.extends[1] then omt.__index = function(self, name) for i,v in ipairs(supers) do if v[name] then return v[name] end end end end
        end
        return obj
    end
    _G[name] = setmetatable(c, cmt)
    return c
end
return setmetatable({}, {__call = function(self, name) return function(tab) if tab.extends or tab.implements then return function(impl) return defineClass(name, tab, impl) end else return defineClass(name, {}, tab) end end end})