middleclass.lua

local _G
    = _G
local setmetatable, assert, type, tostring, pairs, sprintf
    = setmetatable, assert, type, tostring, pairs, string.format

local middleclass = {
    _VERSION        = 'middleclass v3.0.0',
    _DESCRIPTION    = 'Object Orientation for Lua',
    _LICENSE        = [[
        MIT LICENSE

        Copyright (c) 2011 Enrique García Cota

        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.]]
}

local function _setClassDictionariesMetatables(aClass)
    local dict = aClass.__instanceDict
    dict.__index = dict

    local super = aClass.super
    if super then
        local superStatic = super.static
        setmetatable(dict, super.__instanceDict)
        setmetatable(aClass.static, { __index = function(_, k) return dict[k] or superStatic[k] end })
    else
        setmetatable(aClass.static, { __index = function(_, k) return dict[k] end })
    end
end

local function _setClassMetatable(aClass)
    setmetatable(aClass, {
        __tostring = function() return sprintf("class %s", aClass.name) end,
        __index    = aClass.static,
        __newindex = aClass.__instanceDict,
        __call     = function(self, ...) return self:new(...) end
    })
end

local function _createClass(name, super)
    local aClass = {
        name           = name,
        super          = super,
        static         = {},
        __mixins       = {},
        __instanceDict = {}
    }
    aClass.subclasses = setmetatable({}, { __mode = 'k' })

    _setClassDictionariesMetatables(aClass)
    _setClassMetatable(aClass)

    return aClass
end

local function _createLookupMetaMethod(aClass, name)
    return function(...)
        local method = aClass.super[name]
        assert(type(method) == 'function',
               sprintf("class '%s' doesn't implement metamethod '%s'", tostring(aClass), name))
        return method(...)
    end
end

local function _setClassMetamethods(aClass)
    for _, m in ipairs(aClass.__metamethods) do
        aClass[m]= _createLookupMetaMethod(aClass, m)
    end
end

local function _setDefaultInitializeMethod(aClass, super)
    aClass.__init = function(instance, ...)
        return super.__init(instance, ...)
    end
end

local function _includeMixin(aClass, mixin)
    assert(type(mixin) == 'table',
           "mixin must be a table")

    for name, method in pairs(mixin) do
        if name ~= 'included' and name ~= 'static' then
            aClass[name] = method
        end
    end

    if mixin.static then
        for name, method in pairs(mixin.static) do
            aClass.static[name] = method
        end
    end

    if type(mixin.included) == 'function' then
        mixin:included(aClass)
    end

    aClass.__mixins[mixin] = true
end


local Object = _createClass("Object", nil)

Object.static.__metamethods = {
    '__add',
    '__call',
    '__concat',
    '__div',
    '__le',
    '__lt',
    '__mod',
    '__mul',
    '__pow',
    '__sub',
    '__tostring',
    '__unm'
}

function Object.static:allocate()
    assert(type(self) == 'table',
           "Make sure that you are using 'Class:allocate' instead of 'Class.allocate'")

    return setmetatable({ class = self }, self.__instanceDict)
end

function Object.static:new(...)
    local instance = self:allocate()
    instance:__init(...)
    return instance
end

function Object.static:subclass(name)
    assert(type(self) == 'table',
           "Make sure that you are using 'Class:subclass' instead of 'Class.subclass'")
    assert(type(name) == "string",
           "You must provide a name(string) for your class")

    local subclass = _createClass(name, self)
    _setClassMetamethods(subclass)
    _setDefaultInitializeMethod(subclass, self)
    self.subclasses[subclass] = true
    self:subclassed(subclass)

    return subclass
end

function Object.static:subclassed(other)
end

function Object.static:isSubclassOf(other)
    return (
        type(other)      == 'table' and
        type(self)       == 'table' and
        type(self.super) == 'table' and
        (
            self.super == other
            or
            type(self.super.isSubclassOf) == 'function' and
            self.super:isSubclassOf(other)
        )
    )
end

function Object.static:include(...)
    assert(type(self) == 'table',
           "Make sure you that you are using 'Class:include' instead of 'Class.include'")

    local l = select('#', ...)
    for i = 1, l do
        _includeMixin(self, select(i, ...))
    end
    return self
end

function Object.static:includes(mixin)
    return (
        type(mixin)         == 'table' and
        type(self)          == 'table' and
        type(self.__mixins) == 'table' and
        (
            self.__mixins[mixin]
            or
            type(self.super) == 'table' and
            type(self.super.includes) == 'function' and
            self.super:includes(mixin)
        )
    )
end

function Object:__init()
end

function Object:__tostring()
    return sprintf("instance of %s", tostring(self.class))
end

function Object:isInstanceOf(aClass)
    return (
        type(aClass)     == 'table' and
        type(self)       == 'table' and
        type(self.class) == 'table' and
        (
            aClass == self.class
            or
            type(aClass.isSubclassOf) == 'function' and
            self.class:isSubclassOf(aClass)
        )
    )
end

function Object:_areFieldsEqual(other, ...)
    local l = select('#', ...)
    for i = 1, l do
        if self[select(i, ...)] ~= other[select(i, ...)] then
            return false
        end
    end
    return true
end

function Object:_isEquatableTo(other)
    return (
        type(other)       == 'table' and
        type(other.class) == 'table' and
        (
            other.class == self.class
            or
            type(other.isSubclassOf) == 'function' and
            other:isSubclassOf(self.class)
        )
    )
end

function Object:_isEqualTo(other, ...)
    return (
        self:_isEquatableTo(other) and
        self:_areFieldsEqual(other, ...)
    )
end


function middleclass.class(name, super, ...)
    super = super or Object
    return super:subclass(name, ...)
end

middleclass.Object = Object

setmetatable(middleclass, {
    __call = function(_, ...)
        return middleclass.class(...)
    end
})

return middleclass