#66 Add new statistics service to compute statistics for every quizlo…

…rd user

src/service.locator.ts

@@ -5,8 +5,12 @@ import { S3FileService } from './file/s3.service';
 import { SQSQueueService } from './queue/sqs.service';
 import { QuizPersistence } from './quiz/quiz.persistence';
 import { QuizService } from './quiz/quiz.service';
+import { StatisticsService } from './statistics/statistics.service';
 import { UserPersistence } from './user/user.persistence';
 import { UserService } from './user/user.service';
+import { MemoryCache } from './util/cache';
+
+const memoryCache = new MemoryCache();
 
 // auth
 export const authenticationService = new AuthenticationService();
@@ -28,3 +32,6 @@ export const userService = new UserService(userPersistence);
 
 // queue
 export const queueService = new SQSQueueService(quizService);
+
+// statistics
+export const statisticsService = new StatisticsService(userService, quizService, memoryCache);

src/statistics/statistics.service.ts

@@ -0,0 +1,87 @@
+import { QuizService } from '../quiz/quiz.service';
+import { UserService } from '../user/user.service';
+import { Cache } from '../util/cache';
+import { IndividualUserStatistic } from './statistics.dto';
+
+const INDIVIDUAL_STATISTICS_CACHE_KEY = 'invidual-user-statistics';
+
+export class StatisticsService {
+  #userService: UserService;
+  #quizService: QuizService;
+  #cache: Cache;
+  constructor(userService: UserService, quizService: QuizService, cache: Cache) {
+    this.#userService = userService;
+    this.#quizService = quizService;
+    this.#cache = cache;
+  }
+
+  /**
+   * Gets the individual statistics for all users.
+   * @returns An array of users with their statistics.
+   *
+   * @tags worker
+   */
+  async getIndividualUserStatistics(): Promise<IndividualUserStatistic[]> {
+    const cachedResult = await this.#cache.getItem<IndividualUserStatistic[]>(INDIVIDUAL_STATISTICS_CACHE_KEY);
+    if (cachedResult) {
+      return cachedResult;
+    }
+
+    const results: IndividualUserStatistic[] = [];
+    let hasMoreRows = true;
+    let cursor: string | undefined = undefined;
+    while (hasMoreRows) {
+      const { data, hasMoreRows: moreRows } = await this.#userService.getUsers({
+        currentUserId: '1', // Current user id isn't valid here and isn't used for sorting by EMAIL_ASC
+        first: 100,
+        afterId: cursor,
+        sortedBy: 'EMAIL_ASC',
+      });
+
+      for (const user of data) {
+        const { totalQuizCompletions, averageScorePercentage } = await this.#getStatisticsForUser(user.email);
+        results.push({
+          email: user.email,
+          name: user.name,
+          totalQuizCompletions,
+          averageScorePercentage,
+        });
+      }
+
+      cursor = data[data.length - 1]?.id;
+      hasMoreRows = moreRows;
+    }
+
+    return results;
+  }
+
+  /**
+   * Get quiz completion statistics for a single user.
+   * @param userEmail The email of the user to get statistics for.
+   * @returns Total quiz completions and average score percentage for the user.
+   *
+   * @tags worker
+   */
+  async #getStatisticsForUser(userEmail: string) {
+    let hasMoreRows = true;
+    let cursor: string | undefined = undefined;
+    const completionsScores: number[] = [];
+    while (hasMoreRows) {
+      const { stats, cursor: latestCursor } = await this.#quizService.quizScorePercentagesForUser({
+        email: userEmail,
+        first: 100,
+        afterId: cursor,
+      });
+
+      completionsScores.push(...stats);
+
+      cursor = latestCursor;
+      hasMoreRows = !!latestCursor;
+    }
+
+    return {
+      totalQuizCompletions: completionsScores.length,
+      averageScorePercentage: completionsScores.reduce((a, b) => a + b, 0) / completionsScores.length,
+    };
+  }
+}