I think we are being hard on OP (and from a hindsight 20/20 point of view), in many way he acted as the "average normal" person would do, offered to accommodate his friend, expecting that the friend would know and follow social norms given the situation. He was hoping that even when he reversed the question, hoping until the end that his friend will "get it", but the friend didn't. Offering the bed to the friend in this context is not appropriate, as it results in the friend essentially taking advantage of the situation (and making himself look ungrateful) and hurting the OP's feelings.

The OP cannot be faulted for failing predict that the friend will ask for the bed, as this would actually be a low likelihood scenario (very few people will actually do this in such a situation), so the OP (unconsciously and correctly) acted based on the most likely scenario, and he didn't mentioned anything from the start (as in saying "you are welcome to share the room, if you don't mind taking the sofabed") because even such statement invokes some minor social discomfort. In retrospect, this would have been better to have said that than what happened, however, the OP unconsciously played the odds that such a low probability event (maybe 20%?) won't occur (even though, in this case, unfortunately, it did). In other words, the OP acted properly based on the information he had at the time.

So, based on this experience, now the OP has learned that he needs to be more clear up front with this particular friend in the future, if not with all people in similar situations (or at least those that are not very sensitive to the nuances of social conventions/interactions, or have a tendency to overstep boundaries and take advantage of situations).