英语翻译P26页confine下面的一个长难句~有点看不大懂结构了~原句是:If its message were co

英语翻译
P26页confine下面的一个长难句~有点看不大懂结构了~原句是:If its message were confined merely to information--and that in itself would be difficult if not impossible to achieve,for even a detail such as the choice of the color of a shirt is subtly persuasive--advertising would be so boring that no one would pay any attention.这里前半句的information后面破折号的and和后面半句是算哪里的呢?算if里面的还是算后半句?这里if...were confined难道是虚拟语气啊?那么主句就是advertising后面的部分?