Lua Meta API

function get(self)
    self = self or {};
    meta = getmetatable(self) or {};
    return meta;
end

function set(self, meta)
    self = self or {};
    meta = meta or {};
    self = setmetatable(self, meta);
    return self;
end

function mod(self, meta, override)
    self = self or {};
    meta = meta or {};
    smt = get(self);

    for mk, mv in pairs(meta) do
        if override then
            smt[mk] = mv; else
            smt[mk] = smt[mk] or mv; end
    end; return set(self, smt);
end

function clear(self)
    self = self or {};
    return set(self);
end

function setIndex(self, ...)
    newindex = get(self).index or {};
    for ik, iv in pairs({...}) do
        newindex[ik] = iv;
    end

    return mod(self, {
        index = newindex;
        __index = function(object, key)
            local omt = getmetatable(object) or {};
            for _, s in pairs(omt.index or {}) do
                if s[key] then return s[key] end
            end
        end
    });
end

function setCall(self, call)
    return mod(self, {
        __call = function(self, ...)
            return call(self, ...);
        end
    });
end