local module = {};

function module.init(shared)
    local new = {};
    local insert = table.insert;

    local mount = {};
    mount.__index = mount;
    function mount:unmount()
        for _,this in ipairs(self.items) do
            local typeThis = type(this);
            if typeThis == "userdata" then
                this:Destroy();
            elseif typeThis == "table" then
                pcall(function()
                    this.Parent = nil;
                end);
                local destroyThis = this.Destroy;
                if destroyThis then
                    pcall(destroyThis,this);
                end
                --if sef.to when
                -- todo for remove child on parent
            end
        end
    end

    function new.getHolder(item)
		return (type(item) == "table") and (item._holder or item.holder or item.__holder) or item;
	end
	local getHolder = new.getHolder
    -- we should add plugin support
    local pack = table.pack;
    function new.mount(to,...)
        local items = pack(...);
        for _,this in ipairs(items) do
            local thisO = this;
            if type(this) == "table" then
                thisO = this.__object;
                local parent = rawget(this,"__parent");
                if type(parent) == "table" then
                    local parentChild = rawget(parent,"__child");
                    if parentChild then
                        for i,v in pairs(parentChild) do
                            if v == this then
                                parentChild[i] = nil;
                            end
                        end
                    end
                end
                rawset(this,"__parent",to);
            end
            if thisO then
                thisO.Parent = getHolder(to);
            end
            if type(to) == "table" then
                local child = rawget(to,"__child");
                if not child then
                    child = {};
                    rawset(to,"__child",child);
                end
                insert(child,this);
            end
        end
        return setmetatable({to = to,this = items},mount);
    end

    setmetatable(new,{
        __call = function (self,...)
            return new.mount(...);
        end;
    });

    return new;
end

return module;