The collisions system will be done in several parts. The first part is player - walls collisions, and then the last is player - objects collisions.
At the moment i'm working on the player - walls collisions

Detect a collision between the player and the walls is pretty easy because it's only a matter of coordinates. The most difficult part for this type of collisions is that the player has to slide on the wall when a collison occurs.
It's important to not stop the player in this kind of situation, he has the continue his movement by sliding on the wall

It has required some time to think about how to do that, but in the end it worthed it and the player - walls collisions are done. The next step will however be much more complex...