Merge remote-tracking branch 'github.com/master' into webrtc

# Conflicts:
#	back/src/Model/Group.ts
#	back/src/Model/World.ts

back/src/Model/Group.ts

@@ -1,6 +1,6 @@
-import {MessageUserPosition} from "./Websocket/MessageUserPosition";
 import { World } from "./World";
 import { UserInterface } from "./UserInterface";
+import {PositionInterface} from "_Model/PositionInterface";
 import {uuid} from "uuidv4";
 
 export class Group {
@@ -34,17 +34,39 @@ export class Group {
         return this.id;
     }
 
+    /**
+     * Returns the barycenter of all users (i.e. the center of the group)
+     */
+    getPosition(): PositionInterface {
+        let x = 0;
+        let y = 0;
+        // Let's compute the barycenter of all users.
+        this.users.forEach((user: UserInterface) => {
+            x += user.position.x;
+            y += user.position.y;
+        });
+        x /= this.users.length;
+        y /= this.users.length;
+        return {
+            x,
+            y
+        };
+    }
+
     isFull(): boolean {
         return this.users.length >= Group.MAX_PER_GROUP;
     }
 
+    isEmpty(): boolean {
+        return this.users.length <= 1;
+    }
+
     join(user: UserInterface): void
     {
         // Broadcast on the right event
-        for(let i = 0; i < this.users.length; i++){
-            let groupUser : UserInterface = this.users[i];
+        this.users.forEach((groupUser: UserInterface) => {
             this.connectCallback(user.id, groupUser.id, this);
-        }
+        });
         this.users.push(user);
         user.group = this;
     }
@@ -71,7 +93,7 @@ export class Group {
         return stillIn;
     }
 
-    removeFromGroup(users: UserInterface[]): void
+    /*removeFromGroup(users: UserInterface[]): void
     {
         for(let i = 0; i < users.length; i++){
             let user = users[i];
@@ -80,5 +102,32 @@ export class Group {
                 this.users.splice(index, 1);
             }
         }
+    }*/
+
+    leave(user: UserInterface): void
+    {
+        const index = this.users.indexOf(user, 0);
+        if (index === -1) {
+            throw new Error("Could not find user in the group");
+        }
+
+        this.users.splice(index, 1);
+        user.group = undefined;
+
+        // Broadcast on the right event
+        this.users.forEach((groupUser: UserInterface) => {
+            this.disconnectCallback(user.id, groupUser.id);
+        });
+    }
+
+    /**
+     * Let's kick everybody out.
+     * Usually used when there is only one user left.
+     */
+    destroy(): void
+    {
+        this.users.forEach((user: UserInterface) => {
+            this.leave(user);
+        })
     }
 }