feat: add certificates, groups, support system, and moderation

Backend changes:
- Add Certificate generation service with beautiful HTML templates
- Add CourseGroup, GroupMember, GroupMessage models for group collaboration
- Add Homework and HomeworkSubmission models with AI + teacher grading
- Add SupportTicket and TicketMessage models for help desk
- Add Moderation API for admin/moderator course approval workflow
- All new modules: CertificatesModule, GroupsModule, SupportModule, ModerationModule

Frontend changes:
- Add certificate download button when course completed
- Update course page to load enrollment progress from backend
- Integrate lesson completion with backend API

Database schema now supports:
- Course groups with chat functionality
- Homework assignments with dual AI/human grading
- Support ticket system with admin responses
- Full moderation workflow (PENDING_REVIEW -> PUBLISHED/REJECTED)

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/api/src/app.module.ts

@@ -7,6 +7,10 @@ import { UsersModule } from './users/users.module';
 import { CoursesModule } from './courses/courses.module';
 import { CatalogModule } from './catalog/catalog.module';
 import { EnrollmentModule } from './enrollment/enrollment.module';
+import { CertificatesModule } from './certificates/certificates.module';
+import { GroupsModule } from './groups/groups.module';
+import { SupportModule } from './support/support.module';
+import { ModerationModule } from './moderation/moderation.module';
 import { GenerationModule } from './generation/generation.module';
 import { PaymentsModule } from './payments/payments.module';
 import { SearchModule } from './search/search.module';
@@ -42,6 +46,10 @@ import { PrismaModule } from './common/prisma/prisma.module';
     CoursesModule,
     CatalogModule,
     EnrollmentModule,
+    CertificatesModule,
+    GroupsModule,
+    SupportModule,
+    ModerationModule,
     GenerationModule,
     PaymentsModule,
     SearchModule,

apps/api/src/certificates/certificates.controller.ts

@@ -0,0 +1,18 @@
+import { Controller, Get, Param } from '@nestjs/common';
+import { ApiTags, ApiOperation, ApiBearerAuth } from '@nestjs/swagger';
+import { CertificatesService } from './certificates.service';
+import { CurrentUser } from '../auth/decorators/current-user.decorator';
+import { User } from '@coursecraft/database';
+
+@ApiTags('certificates')
+@Controller('certificates')
+@ApiBearerAuth()
+export class CertificatesController {
+  constructor(private certificatesService: CertificatesService) {}
+
+  @Get(':courseId')
+  @ApiOperation({ summary: 'Generate certificate for completed course' })
+  async getCertificate(@Param('courseId') courseId: string, @CurrentUser() user: User): Promise<any> {
+    return this.certificatesService.generateCertificate(user.id, courseId);
+  }
+}

apps/api/src/certificates/certificates.module.ts

@@ -0,0 +1,10 @@
+import { Module } from '@nestjs/common';
+import { CertificatesController } from './certificates.controller';
+import { CertificatesService } from './certificates.service';
+
+@Module({
+  controllers: [CertificatesController],
+  providers: [CertificatesService],
+  exports: [CertificatesService],
+})
+export class CertificatesModule {}

apps/api/src/certificates/certificates.service.ts

@@ -0,0 +1,136 @@
+import { Injectable, NotFoundException } from '@nestjs/common';
+import { PrismaService } from '../common/prisma/prisma.service';
+
+@Injectable()
+export class CertificatesService {
+  constructor(private prisma: PrismaService) {}
+
+  async generateCertificate(userId: string, courseId: string): Promise<any> {
+    const enrollment = await this.prisma.enrollment.findUnique({
+      where: { userId_courseId: { userId, courseId } },
+      include: { course: true, user: true },
+    });
+
+    if (!enrollment) throw new NotFoundException('Not enrolled');
+    if (!enrollment.completedAt) throw new Error('Course not completed yet');
+
+    // Generate certificate HTML (in production, render to PDF using puppeteer or similar)
+    const certificateHtml = this.renderCertificateHTML(
+      enrollment.user.name || enrollment.user.email,
+      enrollment.course.title,
+      new Date(enrollment.completedAt)
+    );
+
+    // In production: save to S3/R2 and return URL
+    // For now, return inline HTML
+    const certificateUrl = `data:text/html;base64,${Buffer.from(certificateHtml).toString('base64')}`;
+
+    await this.prisma.enrollment.update({
+      where: { id: enrollment.id },
+      data: { certificateUrl },
+    });
+
+    return { certificateUrl, html: certificateHtml };
+  }
+
+  private renderCertificateHTML(userName: string, courseTitle: string, completionDate: Date): string {
+    return `<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Сертификат - ${courseTitle}</title>
+  <style>
+    @page { size: A4 landscape; margin: 0; }
+    body {
+      margin: 0;
+      font-family: 'Georgia', serif;
+      background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+      min-height: 100vh;
+      display: flex;
+      align-items: center;
+      justify-center;
+    }
+    .certificate {
+      background: white;
+      width: 1000px;
+      padding: 80px 100px;
+      box-shadow: 0 10px 40px rgba(0,0,0,0.2);
+      border: 12px solid #f8f9fa;
+      position: relative;
+    }
+    .certificate::before {
+      content: '';
+      position: absolute;
+      inset: 30px;
+      border: 2px solid #667eea;
+      pointer-events: none;
+    }
+    h1 {
+      font-size: 48px;
+      text-align: center;
+      color: #667eea;
+      margin: 0 0 20px;
+      font-weight: bold;
+      text-transform: uppercase;
+      letter-spacing: 4px;
+    }
+    h2 {
+      font-size: 24px;
+      text-align: center;
+      color: #333;
+      margin: 0 0 40px;
+      font-weight: normal;
+    }
+    .recipient {
+      text-align: center;
+      font-size: 36px;
+      color: #1a202c;
+      margin: 40px 0;
+      font-weight: bold;
+      border-bottom: 2px solid #667eea;
+      padding-bottom: 10px;
+      display: inline-block;
+      width: 100%;
+    }
+    .course-title {
+      text-align: center;
+      font-size: 28px;
+      color: #4a5568;
+      margin: 40px 0;
+    }
+    .date {
+      text-align: center;
+      color: #718096;
+      margin-top: 60px;
+      font-size: 16px;
+    }
+    .logo {
+      text-align: center;
+      font-size: 20px;
+      color: #667eea;
+      font-weight: bold;
+      margin-bottom: 40px;
+    }
+  </style>
+</head>
+<body>
+  <div class="certificate">
+    <div class="logo">✨ CourseCraft</div>
+    <h1>Сертификат</h1>
+    <h2>о прохождении курса</h2>
+    <div style="text-align: center; margin: 40px 0;">
+      <div style="font-size: 18px; color: #718096; margin-bottom: 10px;">Настоящий сертификат подтверждает, что</div>
+      <div class="recipient">${userName}</div>
+    </div>
+    <div style="text-align: center; margin: 20px 0;">
+      <div style="font-size: 18px; color: #718096; margin-bottom: 10px;">успешно завершил(а) курс</div>
+      <div class="course-title">${courseTitle}</div>
+    </div>
+    <div class="date">
+      Дата выдачи: ${completionDate.toLocaleDateString('ru-RU', { day: '2-digit', month: 'long', year: 'numeric' })}
+    </div>
+  </div>
+</body>
+</html>`;
+  }
+}

apps/api/src/groups/groups.controller.ts

@@ -0,0 +1,32 @@
+import { Controller, Post, Get, Param, Body } from '@nestjs/common';
+import { ApiTags, ApiBearerAuth } from '@nestjs/swagger';
+import { GroupsService } from './groups.service';
+import { CurrentUser } from '../auth/decorators/current-user.decorator';
+import { User } from '@coursecraft/database';
+
+@ApiTags('groups')
+@Controller('groups')
+@ApiBearerAuth()
+export class GroupsController {
+  constructor(private groupsService: GroupsService) {}
+
+  @Post()
+  async createGroup(@Body() body: { courseId: string; name: string; description?: string }, @CurrentUser() user: User): Promise<any> {
+    return this.groupsService.createGroup(body.courseId, user.id, body.name, body.description);
+  }
+
+  @Post(':groupId/members')
+  async addMember(@Param('groupId') groupId: string, @Body('userId') userId: string): Promise<any> {
+    return this.groupsService.addMember(groupId, userId);
+  }
+
+  @Get(':groupId/messages')
+  async getMessages(@Param('groupId') groupId: string, @CurrentUser() user: User): Promise<any> {
+    return this.groupsService.getGroupMessages(groupId, user.id);
+  }
+
+  @Post(':groupId/messages')
+  async sendMessage(@Param('groupId') groupId: string, @Body('content') content: string, @CurrentUser() user: User): Promise<any> {
+    return this.groupsService.sendMessage(groupId, user.id, content);
+  }
+}

apps/api/src/groups/groups.module.ts

@@ -0,0 +1,10 @@
+import { Module } from '@nestjs/common';
+import { GroupsController } from './groups.controller';
+import { GroupsService } from './groups.service';
+
+@Module({
+  controllers: [GroupsController],
+  providers: [GroupsService],
+  exports: [GroupsService],
+})
+export class GroupsModule {}

apps/api/src/groups/groups.service.ts

@@ -0,0 +1,48 @@
+import { Injectable, NotFoundException, ForbiddenException } from '@nestjs/common';
+import { PrismaService } from '../common/prisma/prisma.service';
+
+@Injectable()
+export class GroupsService {
+  constructor(private prisma: PrismaService) {}
+
+  async createGroup(courseId: string, userId: string, name: string, description?: string): Promise<any> {
+    const course = await this.prisma.course.findFirst({ where: { id: courseId, authorId: userId } });
+    if (!course) throw new ForbiddenException('Only course author can create groups');
+
+    return this.prisma.courseGroup.create({
+      data: { courseId, name, description },
+    });
+  }
+
+  async addMember(groupId: string, userId: string, role = 'student'): Promise<any> {
+    return this.prisma.groupMember.create({
+      data: { groupId, userId, role },
+    });
+  }
+
+  async getGroupMessages(groupId: string, userId: string): Promise<any> {
+    const member = await this.prisma.groupMember.findUnique({
+      where: { groupId_userId: { groupId, userId } },
+    });
+    if (!member) throw new ForbiddenException('Not a member of this group');
+
+    return this.prisma.groupMessage.findMany({
+      where: { groupId },
+      include: { user: { select: { id: true, name: true, avatarUrl: true } } },
+      orderBy: { createdAt: 'asc' },
+      take: 100,
+    });
+  }
+
+  async sendMessage(groupId: string, userId: string, content: string): Promise<any> {
+    const member = await this.prisma.groupMember.findUnique({
+      where: { groupId_userId: { groupId, userId } },
+    });
+    if (!member) throw new ForbiddenException('Not a member of this group');
+
+    return this.prisma.groupMessage.create({
+      data: { groupId, userId, content },
+      include: { user: { select: { id: true, name: true, avatarUrl: true } } },
+    });
+  }
+}

apps/api/src/moderation/moderation.controller.ts

@@ -0,0 +1,27 @@
+import { Controller, Get, Post, Param, Body } from '@nestjs/common';
+import { ApiTags, ApiBearerAuth } from '@nestjs/swagger';
+import { ModerationService } from './moderation.service';
+import { CurrentUser } from '../auth/decorators/current-user.decorator';
+import { User } from '@coursecraft/database';
+
+@ApiTags('moderation')
+@Controller('moderation')
+@ApiBearerAuth()
+export class ModerationController {
+  constructor(private moderationService: ModerationService) {}
+
+  @Get('pending')
+  async getPendingCourses(@CurrentUser() user: User): Promise<any> {
+    return this.moderationService.getPendingCourses(user.id);
+  }
+
+  @Post(':courseId/approve')
+  async approveCourse(@Param('courseId') courseId: string, @Body('note') note: string, @CurrentUser() user: User): Promise<any> {
+    return this.moderationService.approveCourse(user.id, courseId, note);
+  }
+
+  @Post(':courseId/reject')
+  async rejectCourse(@Param('courseId') courseId: string, @Body('reason') reason: string, @CurrentUser() user: User): Promise<any> {
+    return this.moderationService.rejectCourse(user.id, courseId, reason);
+  }
+}

apps/api/src/moderation/moderation.module.ts

@@ -0,0 +1,10 @@
+import { Module } from '@nestjs/common';
+import { ModerationController } from './moderation.controller';
+import { ModerationService } from './moderation.service';
+
+@Module({
+  controllers: [ModerationController],
+  providers: [ModerationService],
+  exports: [ModerationService],
+})
+export class ModerationModule {}

apps/api/src/moderation/moderation.service.ts

@@ -0,0 +1,58 @@
+import { Injectable, ForbiddenException } from '@nestjs/common';
+import { PrismaService } from '../common/prisma/prisma.service';
+import { CourseStatus, UserRole } from '@coursecraft/database';
+
+@Injectable()
+export class ModerationService {
+  constructor(private prisma: PrismaService) {}
+
+  async getPendingCourses(userId: string): Promise<any> {
+    const user = await this.prisma.user.findUnique({ where: { id: userId } });
+    if (!user || (user.role !== UserRole.MODERATOR && user.role !== UserRole.ADMIN)) {
+      throw new ForbiddenException('Moderators only');
+    }
+
+    return this.prisma.course.findMany({
+      where: { status: CourseStatus.PENDING_REVIEW },
+      include: {
+        author: { select: { id: true, name: true, email: true } },
+        _count: { select: { chapters: true } },
+      },
+      orderBy: { createdAt: 'asc' },
+    });
+  }
+
+  async approveCourse(userId: string, courseId: string, note?: string): Promise<any> {
+    const user = await this.prisma.user.findUnique({ where: { id: userId } });
+    if (!user || (user.role !== UserRole.MODERATOR && user.role !== UserRole.ADMIN)) {
+      throw new ForbiddenException('Moderators only');
+    }
+
+    return this.prisma.course.update({
+      where: { id: courseId },
+      data: {
+        status: CourseStatus.PUBLISHED,
+        isPublished: true,
+        publishedAt: new Date(),
+        moderationNote: note,
+        moderatedAt: new Date(),
+      },
+    });
+  }
+
+  async rejectCourse(userId: string, courseId: string, reason: string): Promise<any> {
+    const user = await this.prisma.user.findUnique({ where: { id: userId } });
+    if (!user || (user.role !== UserRole.MODERATOR && user.role !== UserRole.ADMIN)) {
+      throw new ForbiddenException('Moderators only');
+    }
+
+    return this.prisma.course.update({
+      where: { id: courseId },
+      data: {
+        status: CourseStatus.REJECTED,
+        moderationNote: reason,
+        moderatedAt: new Date(),
+      },
+    });
+  }
+}

apps/api/src/support/support.controller.ts

@@ -0,0 +1,32 @@
+import { Controller, Post, Get, Param, Body } from '@nestjs/common';
+import { ApiTags, ApiBearerAuth } from '@nestjs/swagger';
+import { SupportService } from './support.service';
+import { CurrentUser } from '../auth/decorators/current-user.decorator';
+import { User } from '@coursecraft/database';
+
+@ApiTags('support')
+@Controller('support')
+@ApiBearerAuth()
+export class SupportController {
+  constructor(private supportService: SupportService) {}
+
+  @Post('tickets')
+  async createTicket(@Body('title') title: string, @CurrentUser() user: User): Promise<any> {
+    return this.supportService.createTicket(user.id, title);
+  }
+
+  @Get('tickets')
+  async getMyTickets(@CurrentUser() user: User): Promise<any> {
+    return this.supportService.getUserTickets(user.id);
+  }
+
+  @Get('tickets/:id/messages')
+  async getMessages(@Param('id') id: string, @CurrentUser() user: User): Promise<any> {
+    return this.supportService.getTicketMessages(id, user.id);
+  }
+
+  @Post('tickets/:id/messages')
+  async sendMessage(@Param('id') id: string, @Body('content') content: string, @CurrentUser() user: User): Promise<any> {
+    return this.supportService.sendMessage(id, user.id, content);
+  }
+}

apps/api/src/support/support.module.ts

@@ -0,0 +1,10 @@
+import { Module } from '@nestjs/common';
+import { SupportController } from './support.controller';
+import { SupportService } from './support.service';
+
+@Module({
+  controllers: [SupportController],
+  providers: [SupportService],
+  exports: [SupportService],
+})
+export class SupportModule {}

apps/api/src/support/support.service.ts

@@ -0,0 +1,40 @@
+import { Injectable } from '@nestjs/common';
+import { PrismaService } from '../common/prisma/prisma.service';
+
+@Injectable()
+export class SupportService {
+  constructor(private prisma: PrismaService) {}
+
+  async createTicket(userId: string, title: string): Promise<any> {
+    return this.prisma.supportTicket.create({
+      data: { userId, title },
+      include: { messages: { include: { user: { select: { name: true } } } } },
+    });
+  }
+
+  async getUserTickets(userId: string): Promise<any> {
+    return this.prisma.supportTicket.findMany({
+      where: { userId },
+      include: { messages: { orderBy: { createdAt: 'desc' }, take: 1 } },
+      orderBy: { updatedAt: 'desc' },
+    });
+  }
+
+  async getTicketMessages(ticketId: string, userId: string): Promise<any> {
+    const ticket = await this.prisma.supportTicket.findFirst({ where: { id: ticketId, userId } });
+    if (!ticket) throw new Error('Ticket not found');
+
+    return this.prisma.ticketMessage.findMany({
+      where: { ticketId },
+      include: { user: { select: { id: true, name: true, avatarUrl: true } } },
+      orderBy: { createdAt: 'asc' },
+    });
+  }
+
+  async sendMessage(ticketId: string, userId: string, content: string): Promise<any> {
+    return this.prisma.ticketMessage.create({
+      data: { ticketId, userId, content, isStaff: false },
+      include: { user: { select: { id: true, name: true } } },
+    });
+  }
+}