Module:LuaClassSystem

-- THIS IS A MODIFIED (NOT THE ORIGINAL) VERSION OF THIS SOFTWARE. -- Copyright (c) 2012-2014 Roland Yonaba --[[ This software is provided 'as-is', without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.

Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be   appreciated but is not required.

2. Altered source versions must be plainly marked as such, and must not be   misrepresented as being the original software.

3. This notice may not be removed or altered from any source distribution. --]]

local pairs, ipairs = pairs, ipairs local assert = assert local setmetatable, getmetatable = setmetatable, getmetatable local type = type local insert = table.insert

-- Internal register local _registry = { class = setmetatable({}, {__mode = 'k'}), object = setmetatable({}, {__mode = 'k'}) }

-- Checks if thing is a kind or whether an 'object' or 'class' local function isObject(thing) return _registry.object[thing] ~= nil end

local function isClass(thing) return _registry.class[thing] ~= nil end

-- Given an object and a class, checks whether the object is an instance of the -- class or one of its superclasses. local function instanceOf(thing, class) assert(isObject(thing), 'instanceof: `thing` must be an LCS object') assert(isClass(class), 'instanceof: `class` must be an LCS class') local thingClass = _registry.object[thing].__superClass if class == thingClass then return true end local thingSuperClass = _registry.class[thingClass].__superClass while thingSuperClass do       if class == thingSuperClass then return true else thingSuperClass = _registry.class[thingSuperClass].__superClass end end -- loop terminated = reached a base class and still haven't found one `thing` is an instance of   return false end

-- tostring local function __tostring(self, ...) if self.tostring then return self:tostring(...) end if isClass(self) then return "LCS class: ?" elseif isObject(self) then return "LCS object: ?" end return tostring(self) end

-- Base metatable local baseClassMt = { __call = function (self, ...) return self:new(...) end, __tostring = __tostring }

local Class

-- Simple helper for building a raw copy of a table -- Only pointers to classes or objects stored as instances are preserved local function deep_copy(t) local r = {} for k, v in pairs(t) do       if type(v) == 'table' then if (_registry.class[v] or _registry.object[v]) then r[k] = v           else r[k] = deep_copy(v) end else r[k] = v       end end return r end

-- Checks for a method in a list of attributes local function checkForMethod(list) for k, attr in pairs(list) do       assert(type(attr) ~= 'function', 'Cannot assign functions as members') end end

-- Instantiation local function instantiateFromClass(self, ...) assert(isClass(self), 'Class constructor must be called from a class') assert(not _registry.class[self].__abstract, 'Cannot instantiate from abstract class') local instance = deep_copy(self) _registry.object[instance] = { __superClass = self, }   local instance = setmetatable(instance, self) if self.init then self.init(instance, ...) end return instance end

-- Class derivation local function extendsFromClass(self, extra_params) assert(isClass(self), 'Inheritance must be called from a class') assert(not _registry.class[self].__final, 'Cannot derive from a final class') local class = Class(extra_params) class.__index = class class.__tostring = __tostring _registry.class[class].__superClass = self _registry.class[self].__subClass[class] = true return setmetatable(class, self) end

-- Abstract class derivation local function abstractExtendsFromClass(self, extra_params) local c = self:extends(extra_params) _registry.class[c].__abstract = true return c end

-- Final class derivation local function finalExtendsFromClass(self, extra_params) local c = self:extends(extra_params) _registry.class[c].__final = true return c end

-- Super methods call local function callFromSuperClass(self, f, ...) assert(isClass(self) or isObject(self), 'attempted to call :super from an unknown object/class') local superClass = getmetatable(self) if not superClass then return nil end local super if isClass(self) then super = superClass else -- must be an object due to the assert above assert(isClass(superClass), 'attempted to call :super with an object that has an unknown class') super = _registry.class[superClass].__superClass end local s = self while s[f] == super[f] do       s = super super = _registry.class[super].__superClass end

-- If the superclass also has a superclass, temporarily set :super to call THAT superclass' methods local supersSuper = _registry.class[super].__superClass if supersSuper then _registry.class[superClass].__superClass = supersSuper end

local method = super[f] local result = method(self, ...)

-- And set the superclass back, if necessary if supersSuper then _registry.class[superClass].__superClass = super end return result end

-- Gets the superclass local function getSuperClass(self) local super = getmetatable(self) return (super ~= baseClassMt and super or nil) end

-- Gets the subclasses local function getSubClasses(self) assert(isClass(self), 'getSubClasses must be called from class') return _registry.class[self].__subClass or {} end

-- Class creation Class = function(members) if members then checkForMethod(members) end local newClass = members and deep_copy(members) or {}                             -- includes class variables newClass.__index = newClass                                                       -- prepares class for inheritance _registry.class[newClass] = {                                                     -- builds information for internal handling __abstract = false, __final = false, __superClass = false, -- Superclasses have no logical dependency on their subclasses. __subClass = setmetatable({}, {__mode = 'k'}), }

newClass.new = instantiateFromClass                                               -- class instanciation newClass.extends = extendsFromClass                                               -- class derivation newClass.abstractExtends = abstractExtendsFromClass                               -- abstract class deriviation newClass.finalExtends = finalExtendsFromClass                                     -- final class deriviation newClass.__call = baseClassMt.__call                                              -- shortcut for instantiation with class call newClass.super = callFromSuperClass                                               -- super method calls handling newClass.getClass = getSuperClass                                                 -- gets the superclass newClass.getSubClasses = getSubClasses                                            -- gets the subclasses newClass.__tostring = __tostring                                                  -- tostring

return setmetatable(newClass, baseClassMt) end

-- Static classes local function abstractClass(members) local class = Class(members) _registry.class[class].__abstract = true return class end

-- Final classes local function finalClass(members) local class = Class(members) _registry.class[class].__final = true return class end

-- These functions are exported for debugging. local debug = {}

-- Given a table `which`, returns `true`/`false` for whether `which` is a known LCS object. -- If given something that is not a table, produces an error. As this is a debug function, -- it checks for errors more extensively. function debug.isKnownObject(which) assert(type(which) == 'table', 'debug.isKnownObject not given a table. This should never happen.') return isObject(which) end

-- Given a table `which`, returns `true`/`false` for whether `which` is a known LCS class. -- If given something that is not a table, produces an error. As this is a debug function, -- it checks for errors more extensively. function debug.isKnownClass(which) assert(type(which) == 'table', 'debug.isKnownClass not given a table. This should never happen.') return isClass(which) end

-- Stands for "e*x*tended type". Like the built-in `type`, returns a string for -- the type of the given object. If the value `which` is a known object or a -- class, returns 'object' or 'class' respectively, otherwise defers to `type`. local function xtype(which) if isObject(which) then return 'object' elseif isClass(which) then return 'class' else return type(which) end end

-- Returns utilities packed in a table (in order to avoid polluting the global environment) return { _VERSION = "2.0.0", class = setmetatable(       {            abstract = abstractClass,            final = finalClass        },        {            __call = function(self, ...) return Class(...) end        }    ), -- custom LCS patches come below instanceOf = instanceOf, xtype = xtype, isObject = isObject, isClass = isClass, debug = debug, }