feat: implement geofence using redis pub-sub

backend-transit/.env.example

@@ -12,3 +12,7 @@ DB_PORT=5432
 DB_USER=transit_user
 DB_PASSWORD=26ab87247a55f86032c943b7e361c475cd3ca8b3b772d82e2fe6a9b5ee0839a3
 DB_NAME=tripz_transit
+
+# --- Redis (Shared with Main Tripz Backend) ---
+REDIS_HOST=tripz-redis
+REDIS_PORT=6379

backend-transit/docker-compose.yml

@@ -22,6 +22,13 @@ services:
       - .env
     depends_on:
       - transit-db
+    networks:
+      - default
+      - tripz-net
 
 volumes:
   transit_pgdata:
+
+networks:
+  tripz-net:
+    external: true

backend-transit/package.json

@@ -13,8 +13,9 @@
     "@nestjs/config": "^3.0.0",
     "@nestjs/core": "^10.0.0",
     "@nestjs/platform-express": "^10.0.0",
-    "@nestjs/typeorm": "^10.0.0",
+    "@nestjs/typeorm": "^11.0.0",
-    "pg": "^8.11.0",
+    "ioredis": "^5.3.2",
+    "pg": "^8.13.1",
     "reflect-metadata": "^0.1.13",
     "rxjs": "^7.8.1",
     "typeorm": "^0.3.17"

backend-transit/src/transit/transit-geofence.service.ts

@@ -0,0 +1,104 @@
+import { Injectable, OnModuleInit, Inject, Logger } from '@nestjs/common';
+import { InjectRepository } from '@nestjs/typeorm';
+import { Repository } from 'typeorm';
+import { TransitBusTrip } from './entities/transit-bus-trip.entity';
+import { TransitStation } from './entities/transit-station.entity';
+import Redis from 'ioredis';
+
+const GEOFENCE_RADIUS_METERS = 150;
+
+@Injectable()
+export class TransitGeofenceService implements OnModuleInit {
+  private readonly logger = new Logger(TransitGeofenceService.name);
+
+  constructor(
+    @Inject('REDIS_CLIENT') private readonly redis: Redis,
+    @InjectRepository(TransitBusTrip) private readonly tripsRepo: Repository<TransitBusTrip>,
+    @InjectRepository(TransitStation) private readonly stationsRepo: Repository<TransitStation>,
+  ) {}
+
+  onModuleInit() {
+    this.redis.subscribe('channel:bus-locations', (err, count) => {
+      if (err) {
+        this.logger.error('Failed to subscribe to bus-locations channel', err);
+      } else {
+        this.logger.log(`Subscribed to ${count} channels.`);
+      }
+    });
+
+    this.redis.on('message', async (channel, message) => {
+      if (channel === 'channel:bus-locations') {
+        try {
+          const data = JSON.parse(message);
+          await this.processBusLocation(data.driverId, data.lat, data.lng);
+        } catch (error) {
+          this.logger.error('Error processing bus location', error);
+        }
+      }
+    });
+  }
+
+  private async processBusLocation(driverId: string, lat: number, lng: number) {
+    // 1. Find active bus trip for this driver
+    const trip = await this.tripsRepo.findOne({
+      where: { driver_id: driverId, status: 'active' },
+    });
+
+    if (!trip) return; // No active trip, ignore
+
+    // 2. Fetch stations for the route
+    // Note: To optimize, this could be cached in memory
+    const stations = await this.stationsRepo.find({
+      where: { route_id: trip.route_id },
+      order: { order_index: 'ASC' },
+    });
+
+    // 3. Find if bus is within any station's radius
+    for (const station of stations) {
+      const distance = this.haversineDistance(lat, lng, Number(station.latitude), Number(station.longitude));
+      
+      if (distance <= GEOFENCE_RADIUS_METERS) {
+        // Bus is inside the geofence of this station!
+        if (trip.current_station_id !== station.id) {
+          this.logger.log(`🚌 Bus for driver ${driverId} arrived at station: ${station.name}`);
+          
+          // Update trip status
+          trip.current_station_id = station.id;
+          await this.tripsRepo.save(trip);
+
+          // Publish event so main Tripz backend can notify passengers via WebSockets
+          this.redis.publish(
+            'channel:bus-arrived',
+            JSON.stringify({
+              tripId: trip.id,
+              driverId,
+              routeId: trip.route_id,
+              stationId: station.id,
+              stationName: station.name,
+            }),
+          );
+        }
+        break; // Found the station, no need to check others
+      }
+    }
+  }
+
+  /**
+   * Calculates the great-circle distance between two points on the Earth's surface.
+   * Returns distance in meters.
+   */
+  private haversineDistance(lat1: number, lon1: number, lat2: number, lon2: number): number {
+    const toRad = (x: number) => (x * Math.PI) / 180;
+    const R = 6371e3; // Earth's radius in meters
+
+    const dLat = toRad(lat2 - lat1);
+    const dLon = toRad(lon2 - lon1);
+
+    const a =
+      Math.sin(dLat / 2) * Math.sin(dLat / 2) +
+      Math.cos(toRad(lat1)) * Math.cos(toRad(lat2)) * Math.sin(dLon / 2) * Math.sin(dLon / 2);
+
+    const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
+    return R * c;
+  }
+}

backend-transit/src/transit/transit.module.ts

@@ -7,6 +7,9 @@ import { TransitBusTrip } from './entities/transit-bus-trip.entity';
 import { TransitTicket } from './entities/transit-ticket.entity';
 import { TransitController } from './transit.controller';
 import { TransitService } from './transit.service';
+import { TransitGeofenceService } from './transit-geofence.service';
+import Redis from 'ioredis';
+import { ConfigService } from '@nestjs/config';
 
 @Module({
   imports: [
@@ -19,7 +22,20 @@ import { TransitService } from './transit.service';
     ]),
   ],
   controllers: [TransitController],
-  providers: [TransitService],
+  providers: [
+    TransitService,
+    TransitGeofenceService,
+    {
+      provide: 'REDIS_CLIENT',
+      inject: [ConfigService],
+      useFactory: (cfg: ConfigService) => {
+        return new Redis({
+          host: cfg.get<string>('REDIS_HOST', 'tripz-redis'),
+          port: cfg.get<number>('REDIS_PORT', 6379),
+        });
+      },
+    },
+  ],
   exports: [TypeOrmModule, TransitService],
 })
 export class TransitModule {}