feat: add absence notification and analytics features

- Implemented AbsenceNotifyView for notifying absence with session details.
- Created AnalyticsView for displaying group analytics and managing students at risk.
- Added ClassAttendanceView for marking attendance in classes.
- Defined new schemas for analytics and attendance in shared package.

apps/backend/src/modules/analytics/features/get-attendee-history/route.ts

@@ -0,0 +1,21 @@
+import { Hono } from 'hono';
+import { problemJson, resultJson, unauthorizedProblem } from '@/http/problem-details';
+import { GetAttendeeHistory } from './use-case';
+
+const route = new Hono();
+
+route.get('/:groupId/attendees/:attendeeId/history', async (c) => {
+  const user = c.get('user');
+  if (!user) {
+    return problemJson(c, unauthorizedProblem(c.req.path));
+  }
+
+  const groupId = c.req.param('groupId');
+  const attendeeId = c.req.param('attendeeId');
+  const useCase = new GetAttendeeHistory();
+  const result = await useCase.execute(groupId, attendeeId, user.id);
+
+  return resultJson(c, result);
+});
+
+export default route;

apps/backend/src/modules/analytics/features/get-attendee-history/use-case.ts

@@ -0,0 +1,83 @@
+import type { PrismaClient } from '@generated/prisma/client';
+import type {
+  AttendanceStatus,
+  AttendeeHistory,
+  ProblemDetails,
+  Result,
+} from '@gruperly/shared';
+import { err, ok } from '@gruperly/shared';
+import { notFoundResourceProblem } from '@/http/problem-builders';
+import prisma from '@/lib/prisma';
+import { type AnalyticsAccessDb, findGroupForUser } from '../../lib/access';
+
+export const HISTORY_SESSIONS_LIMIT = 20;
+
+type GetAttendeeHistoryDeps = {
+  db?: AnalyticsAccessDb & Pick<PrismaClient, 'classSession' | 'attendee' | 'attendance'>;
+};
+
+export class GetAttendeeHistory {
+  constructor(private readonly deps: GetAttendeeHistoryDeps = {}) {}
+
+  async execute(
+    groupId: string,
+    attendeeId: string,
+    userId: string,
+  ): Promise<Result<AttendeeHistory, ProblemDetails>> {
+    const db = this.deps.db ?? prisma;
+
+    const access = await findGroupForUser(db, groupId, userId);
+    if (!access.ok) {
+      return access;
+    }
+
+    const attendee = await db.attendee.findFirst({
+      where: { id: attendeeId, groupId },
+      select: { id: true, fullName: true },
+    });
+    if (!attendee) {
+      return err(notFoundResourceProblem('Attendee', attendeeId));
+    }
+
+    const sessions = await db.classSession.findMany({
+      where: { groupId },
+      orderBy: { startsAt: 'desc' },
+      take: HISTORY_SESSIONS_LIMIT,
+      select: { id: true, startsAt: true },
+    });
+    const sessionIds = sessions.map((session) => session.id);
+
+    const attendances = sessionIds.length
+      ? await db.attendance.findMany({
+        where: { attendeeId, classSessionId: { in: sessionIds } },
+        select: { classSessionId: true, status: true },
+      })
+      : [];
+
+    const statusBySession = new Map<string, AttendanceStatus>(
+      attendances.map((record) => [record.classSessionId, record.status]),
+    );
+
+    const orderedSessions = sessions
+      .slice()
+      .reverse()
+      .map((session) => ({
+        classSessionId: session.id,
+        startsAt: session.startsAt.toISOString(),
+        status: statusBySession.get(session.id) ?? null,
+      }));
+
+    const presentCount = attendances.filter((record) => record.status === 'PRESENT').length;
+    const attendanceRate =
+      sessions.length > 0 ? Math.round((presentCount / sessions.length) * 100) : 0;
+
+    return ok({
+      attendeeId: attendee.id,
+      fullName: attendee.fullName,
+      groupId,
+      groupName: access.value.name,
+      attendanceRate,
+      sessions: orderedSessions,
+    });
+  }
+}

apps/backend/src/modules/analytics/features/get-overview/route.ts

@@ -0,0 +1,20 @@
+import { Hono } from 'hono';
+import { problemJson, resultJson, unauthorizedProblem } from '@/http/problem-details';
+import { GetGroupAnalytics } from './use-case';
+
+const route = new Hono();
+
+route.get('/:groupId/analytics', async (c) => {
+  const user = c.get('user');
+  if (!user) {
+    return problemJson(c, unauthorizedProblem(c.req.path));
+  }
+
+  const groupId = c.req.param('groupId');
+  const useCase = new GetGroupAnalytics();
+  const result = await useCase.execute(groupId, user.id);
+
+  return resultJson(c, result);
+});
+
+export default route;

apps/backend/src/modules/analytics/features/get-overview/use-case.ts

@@ -0,0 +1,55 @@
+import type { PrismaClient } from '@generated/prisma/client';
+import type { GroupAnalytics, ProblemDetails, Result } from '@gruperly/shared';
+import { ok } from '@gruperly/shared';
+import prisma from '@/lib/prisma';
+import { type AnalyticsAccessDb, findGroupForUser } from '../../lib/access';
+
+export const ANALYTICS_WINDOW_MS = 30 * 24 * 60 * 60 * 1000;
+
+type GetGroupAnalyticsDeps = {
+  db?: AnalyticsAccessDb & Pick<PrismaClient, 'classSession' | 'attendance' | 'slotRelease'>;
+  now?: Date;
+};
+
+export class GetGroupAnalytics {
+  constructor(private readonly deps: GetGroupAnalyticsDeps = {}) {}
+
+  async execute(
+    groupId: string,
+    userId: string,
+  ): Promise<Result<GroupAnalytics, ProblemDetails>> {
+    const db = this.deps.db ?? prisma;
+    const now = this.deps.now ?? new Date();
+    const since = new Date(now.getTime() - ANALYTICS_WINDOW_MS);
+
+    const access = await findGroupForUser(db, groupId, userId);
+    if (!access.ok) {
+      return access;
+    }
+
+    const [sessions, attendances, recoveredSlots] = await Promise.all([
+      db.classSession.findMany({
+        where: { groupId, startsAt: { gte: since } },
+        select: { id: true },
+      }),
+      db.attendance.findMany({
+        where: { classSession: { groupId, startsAt: { gte: since } } },
+        select: { status: true },
+      }),
+      db.slotRelease.count({
+        where: { classSession: { groupId, startsAt: { gte: since } } },
+      }),
+    ]);
+
+    const totalClasses = sessions.length;
+    const totalMarked = attendances.length;
+    const totalPresent = attendances.filter((record) => record.status === 'PRESENT').length;
+
+    return ok({
+      attendanceRate: totalMarked > 0 ? Math.round((totalPresent / totalMarked) * 100) : 0,
+      totalPresent,
+      totalClasses,
+      recoveredSlots,
+    });
+  }
+}

apps/backend/src/modules/analytics/features/get-students-at-risk/route.ts

@@ -0,0 +1,20 @@
+import { Hono } from 'hono';
+import { problemJson, resultJson, unauthorizedProblem } from '@/http/problem-details';
+import { GetStudentsAtRisk } from './use-case';
+
+const route = new Hono();
+
+route.get('/:groupId/students-at-risk', async (c) => {
+  const user = c.get('user');
+  if (!user) {
+    return problemJson(c, unauthorizedProblem(c.req.path));
+  }
+
+  const groupId = c.req.param('groupId');
+  const useCase = new GetStudentsAtRisk();
+  const result = await useCase.execute(groupId, user.id);
+
+  return resultJson(c, result);
+});
+
+export default route;

apps/backend/src/modules/analytics/features/get-students-at-risk/use-case.ts

@@ -0,0 +1,122 @@
+import type { PrismaClient } from '@generated/prisma/client';
+import type {
+  AttendanceStatus,
+  ProblemDetails,
+  Result,
+  StudentAtRisk,
+  StudentsAtRisk,
+} from '@gruperly/shared';
+import { ok } from '@gruperly/shared';
+import prisma from '@/lib/prisma';
+import { type AnalyticsAccessDb, findGroupForUser } from '../../lib/access';
+import {
+  classifyRisk,
+  lastAttendedAt,
+  monthlyAttendanceRate,
+  trailingAbsentStreak,
+} from '../../lib/risk';
+import { ANALYTICS_WINDOW_MS } from '../get-overview/use-case';
+
+type GetStudentsAtRiskDeps = {
+  db?: AnalyticsAccessDb & Pick<PrismaClient, 'classSession' | 'attendee' | 'attendance'>;
+  now?: Date;
+};
+
+type AttendanceStreamRow = {
+  attendeeId: string;
+  status: AttendanceStatus;
+  classSession: { startsAt: Date };
+};
+
+export class GetStudentsAtRisk {
+  constructor(private readonly deps: GetStudentsAtRiskDeps = {}) {}
+
+  async execute(
+    groupId: string,
+    userId: string,
+  ): Promise<Result<StudentsAtRisk, ProblemDetails>> {
+    const db = this.deps.db ?? prisma;
+    const now = this.deps.now ?? new Date();
+    const since = new Date(now.getTime() - ANALYTICS_WINDOW_MS);
+
+    const access = await findGroupForUser(db, groupId, userId);
+    if (!access.ok) {
+      return access;
+    }
+
+    const [windowSessions, attendees, attendances] = await Promise.all([
+      db.classSession.findMany({
+        where: { groupId, startsAt: { gte: since } },
+        select: { id: true },
+      }),
+      db.attendee.findMany({
+        where: { groupId, status: 'ACTIVE' },
+        select: { id: true, fullName: true, phone: true },
+      }),
+      db.attendance.findMany({
+        where: { attendee: { groupId } },
+        select: {
+          attendeeId: true,
+          status: true,
+          classSession: { select: { startsAt: true } },
+        },
+        orderBy: { classSession: { startsAt: 'desc' } },
+      }),
+    ]);
+
+    const totalWindowSessions = windowSessions.length;
+    const streamByAttendee = groupAttendanceByAttendee(attendances);
+
+    const atRisk: StudentAtRisk[] = [];
+    for (const attendee of attendees) {
+      const stream = (streamByAttendee.get(attendee.id) ?? []).map((row) => ({
+        status: row.status,
+        occurredAt: row.classSession.startsAt,
+      }));
+      const consecutiveAbsences = trailingAbsentStreak(stream);
+      const attendedAt = lastAttendedAt(stream);
+      const monthlyRate = monthlyAttendanceRate(
+        stream.filter((entry) => entry.occurredAt.getTime() >= since.getTime()),
+        totalWindowSessions,
+      );
+      const riskLevel = classifyRisk(consecutiveAbsences, monthlyRate);
+      if (!riskLevel) {
+        continue;
+      }
+      atRisk.push({
+        attendeeId: attendee.id,
+        fullName: attendee.fullName,
+        phone: attendee.phone,
+        riskLevel,
+        consecutiveAbsences,
+        lastAttendedAt: attendedAt ? attendedAt.toISOString() : null,
+        monthlyAttendanceRate: monthlyRate,
+      });
+    }
+
+    atRisk.sort((a, b) => {
+      if (a.riskLevel !== b.riskLevel) {
+        return a.riskLevel === 'HIGH' ? -1 : 1;
+      }
+      if (a.consecutiveAbsences !== b.consecutiveAbsences) {
+        return b.consecutiveAbsences - a.consecutiveAbsences;
+      }
+      return a.monthlyAttendanceRate - b.monthlyAttendanceRate;
+    });
+
+    return ok({
+      groupName: access.value.name,
+      data: atRisk,
+    });
+  }
+}
+
+function groupAttendanceByAttendee(rows: AttendanceStreamRow[]): Map<string, AttendanceStreamRow[]> {
+  const byAttendee = new Map<string, AttendanceStreamRow[]>();
+  for (const row of rows) {
+    const list = byAttendee.get(row.attendeeId) ?? [];
+    list.push(row);
+    byAttendee.set(row.attendeeId, list);
+  }
+  return byAttendee;
+}

apps/backend/src/modules/analytics/features/update-attendee-status/route.ts

@@ -0,0 +1,24 @@
+import type { UpdateStudentStatus } from '@gruperly/shared';
+import { UpdateStudentStatusSchema } from '@gruperly/shared';
+import { Hono } from 'hono';
+import { problemJson, resultJson, unauthorizedProblem } from '@/http/problem-details';
+import { validate } from '@/http/validate';
+import { UpdateAttendeeStatus } from './use-case';
+
+const route = new Hono();
+
+route.post('/:studentId/status', validate.json(UpdateStudentStatusSchema), async (c) => {
+  const user = c.get('user');
+  if (!user) {
+    return problemJson(c, unauthorizedProblem(c.req.path));
+  }
+
+  const studentId = c.req.param('studentId');
+  const payload = c.req.valid('json') as UpdateStudentStatus;
+  const useCase = new UpdateAttendeeStatus();
+  const result = await useCase.execute(studentId, user.id, payload);
+
+  return resultJson(c, result);
+});
+
+export default route;

apps/backend/src/modules/analytics/features/update-attendee-status/use-case.ts

@@ -0,0 +1,53 @@
+import type { PrismaClient } from '@generated/prisma/client';
+import type {
+  ProblemDetails,
+  Result,
+  UpdateStudentStatus,
+  UpdateStudentStatusResult,
+} from '@gruperly/shared';
+import { err, ok } from '@gruperly/shared';
+import { noGroupAccessProblem, notFoundResourceProblem } from '@/http/problem-builders';
+import prisma from '@/lib/prisma';
+
+type UpdateAttendeeStatusDeps = {
+  db?: Pick<PrismaClient, 'attendee'>;
+};
+
+export class UpdateAttendeeStatus {
+  constructor(private readonly deps: UpdateAttendeeStatusDeps = {}) {}
+
+  async execute(
+    studentId: string,
+    userId: string,
+    payload: UpdateStudentStatus,
+  ): Promise<Result<UpdateStudentStatusResult, ProblemDetails>> {
+    const db = this.deps.db ?? prisma;
+
+    const attendee = await db.attendee.findUnique({
+      where: { id: studentId },
+      include: { group: { include: { members: { where: { userId } } } } },
+    });
+
+    if (!attendee) {
+      return err(notFoundResourceProblem('Attendee', studentId));
+    }
+
+    const isOwner = attendee.group.createdById === userId;
+    const isMember = attendee.group.members.length > 0;
+    if (!isOwner && !isMember) {
+      return err(noGroupAccessProblem());
+    }
+
+    if (attendee.status === payload.status) {
+      return ok({ attendeeId: studentId, status: payload.status });
+    }
+
+    const updated = await db.attendee.update({
+      where: { id: studentId },
+      data: { status: payload.status },
+      select: { id: true, status: true },
+    });
+
+    return ok({ attendeeId: updated.id, status: updated.status });
+  }
+}