Adding batched messages + the notion of notifier / zones (not plugged in the system yet)

back/src/Model/PositionNotifier.ts

@@ -0,0 +1,106 @@
+/**
+ * Tracks the position of every player on the map, and sends notifications to the players interested in knowing about the move
+ * (i.e. players that are looking at the zone the player is currently in)
+ *
+ * Internally, the PositionNotifier works with Zones. A zone is a square area of a map.
+ * Each player is in a given zone, and each player tracks one or many zones (depending on the player viewport)
+ *
+ * The PositionNotifier is important for performance. It allows us to send the position of players only to a restricted
+ * number of players around the current player.
+ */
+import {UserEntersCallback, UserLeavesCallback, UserMovesCallback, Zone} from "./Zone";
+import {PointInterface} from "_Model/Websocket/PointInterface";
+import {UserInterface} from "_Model/UserInterface";
+import {ViewportInterface} from "_Model/Websocket/ViewportMessage";
+
+interface ZoneDescriptor {
+    i: number;
+    j: number;
+}
+
+export class PositionNotifier {
+
+    // TODO: we need a way to clean the zones if noone is in the zone and noone listening (to free memory!)
+
+    private zones: Zone[][] = [];
+
+    constructor(private zoneWidth: number, private zoneHeight: number, private onUserEnters: UserEntersCallback, private onUserMoves: UserMovesCallback, private onUserLeaves: UserLeavesCallback) {
+    }
+
+    private getZoneDescriptorFromCoordinates(x: number, y: number): ZoneDescriptor {
+        return {
+            i: Math.floor(x / this.zoneWidth),
+            j: Math.floor(y / this.zoneHeight),
+        }
+    }
+
+    public setViewport(user: UserInterface, viewport: ViewportInterface): void {
+        if (viewport.left > viewport.right || viewport.top > viewport.bottom) {
+            console.warn('Invalid viewport received: ', viewport);
+            return;
+        }
+
+        const oldZones = user.listenedZones;
+        const newZones = new Set<Zone>();
+
+        const topLeftDesc = this.getZoneDescriptorFromCoordinates(viewport.left, viewport.top);
+        const bottomRightDesc = this.getZoneDescriptorFromCoordinates(viewport.right, viewport.bottom);
+
+        for (let j = topLeftDesc.j; j <= bottomRightDesc.j; j++) {
+            for (let i = topLeftDesc.i; i <= bottomRightDesc.i; i++) {
+                newZones.add(this.getZone(i, j));
+            }
+        }
+
+        const addedZones = [...newZones].filter(x => !oldZones.has(x));
+        const removedZones = [...oldZones].filter(x => !newZones.has(x));
+
+        for (const zone of addedZones) {
+            zone.startListening(user);
+        }
+        for (const zone of removedZones) {
+            zone.stopListening(user);
+        }
+    }
+
+    public updatePosition(user: UserInterface, userPosition: PointInterface): void {
+        // Did we change zone?
+        const oldZoneDesc = this.getZoneDescriptorFromCoordinates(user.position.x, user.position.y);
+        const newZoneDesc = this.getZoneDescriptorFromCoordinates(userPosition.x, userPosition.y);
+
+        if (oldZoneDesc.i != newZoneDesc.i || oldZoneDesc.j != newZoneDesc.j) {
+            const oldZone = this.getZone(oldZoneDesc.i, oldZoneDesc.j);
+            const newZone = this.getZone(newZoneDesc.i, newZoneDesc.j);
+
+            // Leave old zone
+            oldZone.leave(user, newZone);
+
+            // Enter new zone
+            newZone.enter(user, oldZone, userPosition);
+        } else {
+            const zone = this.getZone(oldZoneDesc.i, oldZoneDesc.j);
+            zone.move(user, userPosition);
+        }
+    }
+
+    public leave(user: UserInterface): void {
+        const oldZoneDesc = this.getZoneDescriptorFromCoordinates(user.position.x, user.position.y);
+        const oldZone = this.getZone(oldZoneDesc.i, oldZoneDesc.j);
+        oldZone.leave(user, null);
+    }
+
+    private getZone(i: number, j: number): Zone {
+        let zoneRow = this.zones[j];
+        if (zoneRow === undefined) {
+            zoneRow = new Array<Zone>();
+            this.zones[j] = zoneRow;
+        }
+
+        let zone = this.zones[j][i];
+        if (zone === undefined) {
+            zone = new Zone(this.onUserEnters, this.onUserMoves, this.onUserLeaves);
+            this.zones[j][i] = zone;
+        }
+        return zone;
+    }
+}