Add statistics generation

libs/api/event/feature/src/queries/get-event-statistics.handler.ts

@@ -1,40 +1,118 @@
 import { EventRepository } from '@event-participation-trends/api/event/data-access';
-import { GetEventStatisticsQuery, IGetEventStatisticsResponse } from '@event-participation-trends/api/event/util';
+import {
+  GetEventStatisticsQuery,
+  IGetEventStatisticsResponse,
+} from '@event-participation-trends/api/event/util';
 import { UserRepository } from '@event-participation-trends/api/user/data-access';
 import { QueryHandler, IQueryHandler } from '@nestjs/cqrs';
 import { Types } from 'mongoose';
 
 @QueryHandler(GetEventStatisticsQuery)
-export class GetEventStatisticsHandler implements IQueryHandler<GetEventStatisticsQuery, IGetEventStatisticsResponse> {
-    constructor(
-        private readonly eventRepository: EventRepository,
-        private readonly userRepository: UserRepository,
-    ) {}
-
-    async execute(query: GetEventStatisticsQuery) {
-
-        const eventIdObj = <Types.ObjectId> <unknown> query.request.eventId;
-        const devices =  await this.eventRepository.getDevicePosotions(eventIdObj);
-
-        let total_attendance =0;
-        let average_attendance =0;
-        let peak_attendance= 0;
-        let turnover_rate =0;
-        let average_attendance_time =0;
-        let max_attendance_time =0;
-
-        //compute statistics begin
-
-        //compute statistics end
-
-        return <IGetEventStatisticsResponse> {
-            total_attendance: total_attendance,
-            average_attendance: average_attendance,
-            peak_attendance: peak_attendance,
-            turnover_rate: turnover_rate,
-            average_attendance_time: average_attendance_time,
-            max_attendance_time: max_attendance_time,
+export class GetEventStatisticsHandler
+  implements
+    IQueryHandler<GetEventStatisticsQuery, IGetEventStatisticsResponse>
+{
+  constructor(
+    private readonly eventRepository: EventRepository,
+    private readonly userRepository: UserRepository
+  ) {}
+
+  async execute(query: GetEventStatisticsQuery) {
+    const eventIdObj = <Types.ObjectId>(<unknown>query.request.eventId);
+    const events = await this.eventRepository.getDevicePosotions(eventIdObj);
+
+    let total_attendance = 0;
+    let average_attendance = 0;
+    let peak_attendance = 0;
+    let turnover_rate = 0;
+    let average_attendance_time = 0;
+    let max_attendance_time = 0;
+
+    if (events.length == 0) {
+      return <IGetEventStatisticsResponse>{
+        total_attendance: total_attendance,
+        average_attendance: average_attendance,
+        peak_attendance: peak_attendance,
+        turnover_rate: turnover_rate,
+        average_attendance_time: average_attendance_time,
+        max_attendance_time: max_attendance_time,
+      };
+    }
+
+    turnover_rate = 0;
+
+    const devices = events[0].Devices ? events[0].Devices : [];
+
+    //compute statistics begin
+
+    const uniqueDevices = new Set();
+
+    const devicesOverTime = new Map<Date, Set<number>>();
+    const deviceTimeRange = new Map<number, { start: Date; end: Date }>();
+
+    // iterate over all devices
+
+    for (const device of devices) {
+      if (!device.timestamp || !device.id) {
+        continue;
+      }
+
+      uniqueDevices.add(device.id);
+
+      if (deviceTimeRange.has(device.id)) {
+        const range = deviceTimeRange.get(device.id);
+        if (range) {
+          if (device.timestamp < range.start) {
+            range.start = device.timestamp;
+          }
+          if (device.timestamp > range.end) {
+            range.end = device.timestamp;
+          }
         }
+      }
+
+      const deviceSet = devicesOverTime.get(device.timestamp);
+      if (deviceSet) {
+        deviceSet.add(device.id);
+      } else {
+        devicesOverTime.set(device.timestamp, new Set([device.id]));
+      }
+    }
+
+    // compute average attendance
+
+    let total_unique_devices = 0;
+
+    for (const [key, value] of devicesOverTime.entries()) {
+      if (value.size > peak_attendance) {
+        peak_attendance = value.size;
+      }
+      total_unique_devices += value.size;
     }
 
-}
+    let total_attendance_time = 0;
+
+    for (const [key, value] of deviceTimeRange.entries()) {
+      const diff = value.end.getTime() - value.start.getTime();
+      total_attendance_time += diff;
+      if (diff > max_attendance_time) {
+        max_attendance_time = diff;
+      }
+    }
+
+    total_attendance = uniqueDevices.size;
+    average_attendance = total_unique_devices / devicesOverTime.size;
+    average_attendance_time = total_attendance_time / deviceTimeRange.size;
+
+    //compute statistics end
+
+    return <IGetEventStatisticsResponse>{
+      total_attendance: total_attendance,
+      average_attendance: average_attendance,
+      peak_attendance: peak_attendance,
+      turnover_rate: turnover_rate,
+      average_attendance_time: average_attendance_time,
+      max_attendance_time: max_attendance_time,
+    };
+  }
+}