Left column: (top) List of rooms I'm inside, (bottom) list of private conversations
Central column : chat windows, with a bar at the top showing chat room name, creator & banner
RIght column: list of people in the current room or current private chat
Using ionic framework (http://ionicframework.com/) or just plain AngularJS with http://angular-ui.github.io/bootstrap/
Idea of layout:
Left column: (top) List of rooms I'm inside, (bottom) list of private conversations Central column : chat windows, with a bar at the top showing chat room name, creator & banner RIght column: list of people in the current room or current private chat