feat: add most popular courses statistics (#257)

* feat: add most popular courses statistics

* feat: apply feedback, renaming of functions

apps/api/src/statistics/repositories/statistics.repository.ts

@@ -1,9 +1,11 @@
 import { Inject, Injectable } from "@nestjs/common";
-import { eq, sql } from "drizzle-orm";
+import { desc, eq, sql } from "drizzle-orm";
 
 import { DatabasePg } from "src/common";
 import { LessonProgress } from "src/lessons/schemas/lesson.types";
 import {
+  courses,
+  courseStatisticsPerTeacherMaterialized,
   lessons,
   quizAttempts,
   studentCourses,
@@ -131,6 +133,19 @@ export class StatisticsRepository {
     return result;
   }
 
+  async getFiveMostPopularCourses(userId: string) {
+    return await this.db
+      .select({
+        courseName: courses.title,
+        studentCount: courseStatisticsPerTeacherMaterialized.studentCount,
+      })
+      .from(courseStatisticsPerTeacherMaterialized)
+      .innerJoin(courses, eq(courseStatisticsPerTeacherMaterialized.courseId, courses.id))
+      .where(eq(courseStatisticsPerTeacherMaterialized.teacherId, userId))
+      .orderBy(desc(courseStatisticsPerTeacherMaterialized.studentCount))
+      .limit(5);
+  }
+
   async createQuizAttempt(data: {
     userId: string;
     courseId: string;

apps/api/src/statistics/schemas/userStats.schema.ts

@@ -57,6 +57,15 @@ export const UserStatsSchema = Type.Object({
   ]),
 });
 
+export const PopularCourseStatsSchema = Type.Object({
+  courseName: Type.String(),
+  studentCount: Type.Number(),
+});
+
+export const TeacherStatsSchema = Type.Object({
+  fiveMostPopularCourses: Type.Array(PopularCourseStatsSchema),
+});
+
 const UserStatisticSchema = Type.Object({
   currentStreak: Type.Number(),
   longestStreak: Type.Number(),
@@ -67,3 +76,4 @@ const UserStatisticSchema = Type.Object({
 export type UserStats = Static<typeof UserStatsSchema>;
 export type StatsByMonth = Static<typeof StatsByMonthSchema>;
 export type UserStatistic = Static<typeof UserStatisticSchema>;
+export type TeacherStats = Static<typeof TeacherStatsSchema>;

apps/api/src/statistics/statistics.controller.ts

@@ -0,0 +1,40 @@
+import { Controller, Get, UseGuards } from "@nestjs/common";
+import { Validate } from "nestjs-typebox";
+
+import { baseResponse, BaseResponse, UUIDType } from "src/common";
+import { Roles } from "src/common/decorators/roles.decorator";
+import { CurrentUser } from "src/common/decorators/user.decorator";
+import { RolesGuard } from "src/common/guards/roles.guard";
+import { USER_ROLES } from "src/users/schemas/user-roles";
+
+import { TeacherStatsSchema, UserStatsSchema } from "./schemas/userStats.schema";
+import { StatisticsService } from "./statistics.service";
+
+import type { TeacherStats, UserStats } from "./schemas/userStats.schema";
+
+@UseGuards(RolesGuard)
+@Controller("statistics")
+export class StatisticsController {
+  constructor(private statisticsService: StatisticsService) {}
+
+  @Get("user-stats")
+  @Validate({
+    response: baseResponse(UserStatsSchema),
+  })
+  async getUserStatistics(
+    @CurrentUser("userId") currentUserId: UUIDType,
+  ): Promise<BaseResponse<UserStats>> {
+    return new BaseResponse(await this.statisticsService.getUserStats(currentUserId));
+  }
+
+  @Get("teacher-stats")
+  @Roles(USER_ROLES.admin, USER_ROLES.tutor)
+  @Validate({
+    response: baseResponse(TeacherStatsSchema),
+  })
+  async getTeacherStats(
+    @CurrentUser("userId") currentUserId: UUIDType,
+  ): Promise<BaseResponse<TeacherStats>> {
+    return new BaseResponse(await this.statisticsService.getTeacherStats(currentUserId));
+  }
+}

apps/api/src/statistics/statistics.module.ts

@@ -4,8 +4,8 @@ import { CqrsModule } from "@nestjs/cqrs";
 import { LessonsRepository } from "src/lessons/repositories/lessons.repository";
 import { StatisticsRepository } from "src/statistics/repositories/statistics.repository";
 
-import { StatisticsController } from "./api/statistics.controller";
 import { StatisticsHandler } from "./handlers/statistics.handler";
+import { StatisticsController } from "./statistics.controller";
 import { StatisticsService } from "./statistics.service";
 
 @Module({

apps/api/src/statistics/statistics.service.ts

@@ -52,6 +52,15 @@ export class StatisticsService {
     };
   }
 
+  async getTeacherStats(userId: string) {
+    const fiveMostPopularCourses =
+      await this.statisticsRepository.getFiveMostPopularCourses(userId);
+
+    return {
+      fiveMostPopularCourses,
+    };
+  }
+
   async createQuizAttempt(data: {
     userId: string;
     courseId: string;

apps/api/src/storage/migrations/0012_create_materialized_view_course_statistics_per_teacher.sql

@@ -0,0 +1,28 @@
+ALTER TABLE "student_lessons_progress" ADD COLUMN "completed_as_freemium" boolean DEFAULT false NOT NULL;
+
+CREATE MATERIALIZED VIEW
+  "course_statistics_per_teacher" AS
+SELECT
+  c.author_id AS teacher_id,
+  c.id AS course_id,
+  COUNT(sc.id) AS student_count,
+  SUM(
+    CASE
+      WHEN sc.state = 'completed' THEN 1
+      ELSE 0
+    END
+  ) AS completed_student_count,
+  COUNT(
+    DISTINCT CASE
+      WHEN slp.completed_as_freemium = true THEN sc.student_id
+      ELSE NULL
+    END
+  ) AS purchased_after_freemium_count
+FROM
+  courses c
+  LEFT JOIN student_courses sc ON c.id = sc.course_id
+  LEFT JOIN student_lessons_progress slp ON c.id = slp.course_id
+  AND slp.completed_at IS NOT NULL
+GROUP BY
+  c.author_id,
+  c.id;