backend/src/courses/courses.service.ts

import {
  Injectable,
  NotFoundException,
  ForbiddenException,
} from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { Course } from '../entities/course.entity';
import { UserCourse } from '../entities/user-course.entity';
import { UserStar } from '../entities/user-star.entity';
import { Comment } from '../entities/comment.entity';

@Injectable()
export class CoursesService {
  constructor(
    @InjectRepository(Course)
    private courseRepository: Repository<Course>,
    @InjectRepository(UserCourse)
    private userCourseRepository: Repository<UserCourse>,
    @InjectRepository(UserStar)
    private userStarRepository: Repository<UserStar>,
    @InjectRepository(Comment)
    private commentRepository: Repository<Comment>,
  ) {}

  async findAll() {
    return this.courseRepository.find({
      where: { isActive: true },
      select: [
        'id',
        'title',
        'description',
        'coverImage',
        'price',
        'category',
        'viewCount',
        'likeCount',
        'starCount',
      ],
      order: { createdAt: 'DESC' },
    });
  }

  async findOne(id: number) {
    const course = await this.courseRepository.findOne({
      where: { id, isActive: true },
      select: [
        'id',
        'title',
        'description',
        'coverImage',
        'price',
        'category',
        'viewCount',
        'likeCount',
        'starCount',
      ],
    });

    if (!course) {
      throw new NotFoundException('Course not found');
    }

    return course;
  }

  async incrementViewCount(id: number) {
    await this.courseRepository.increment({ id }, 'viewCount', 1);
  }

  async toggleLike(id: number) {
    const course = await this.courseRepository.findOne({ where: { id } });
    if (course) {
      await this.courseRepository.increment({ id }, 'likeCount', 1);
    }
  }

  async toggleStar(courseId: number, userId: number) {
    const existingStar = await this.userStarRepository.findOne({
      where: { courseId, userId },
    });

    if (existingStar) {
      await this.userStarRepository.remove(existingStar);
      await this.courseRepository.decrement({ id: courseId }, 'starCount', 1);
    } else {
      const newStar = this.userStarRepository.create({ courseId, userId });
      await this.userStarRepository.save(newStar);
      await this.courseRepository.increment({ id: courseId }, 'starCount', 1);
    }
  }

  async getUserStars(userId: number) {
    const userStars = await this.userStarRepository.find({
      where: { userId },
      relations: ['course'],
    });

    return userStars.map((us) => ({
      id: us.course.id,
      title: us.course.title,
      coverImage: us.course.coverImage,
      description: us.course.description,
      price: us.course.price,
      category: us.course.category,
      viewCount: us.course.viewCount,
      likeCount: us.course.likeCount,
      starCount: us.course.starCount,
    }));
  }

  async getUserCourses(userId: number) {
    const userCourses = await this.userCourseRepository.find({
      where: { userId },
      relations: ['course'],
    });

    return userCourses.map((uc) => ({
      id: uc.course.id,
      title: uc.course.title,
      coverImage: uc.course.coverImage,
      expiredAt: uc.expiredAt,
    }));
  }

  async getComments(courseId: number) {
    const comments = await this.commentRepository.find({
      where: { courseId },
      relations: ['user', 'replyToComment', 'replyToComment.user'],
      order: { createdAt: 'ASC' },
    });
    
    return comments.map(c => ({
      id: c.id,
      courseId: c.courseId,
      userId: c.userId,
      parentId: c.parentId,
      replyToCommentId: c.replyToCommentId,
      content: c.content,
      createdAt: c.createdAt,
      user: {
        id: c.user.id,
        nickname: c.user.nickname,
        avatar: c.user.avatar,
        isVip: c.user.isVip,
      },
      replyToUser: c.replyToComment ? {
        id: c.replyToComment.user.id,
        nickname: c.replyToComment.user.nickname,
      } : undefined
    }));
  }

  async addComment(courseId: number, userId: number, content: string, parentId?: number, replyToCommentId?: number) {
    const course = await this.courseRepository.findOne({ where: { id: courseId } });
    if (!course) throw new NotFoundException('Course not found');

    const comment = this.commentRepository.create({
      courseId,
      userId,
      content,
      parentId,
      replyToCommentId,
    });
    await this.commentRepository.save(comment);

    const savedComment = await this.commentRepository.findOne({
      where: { id: comment.id },
      relations: ['user', 'replyToComment', 'replyToComment.user']
    });

    if (!savedComment) throw new NotFoundException('Comment not found after save');

    return {
      id: savedComment.id,
      courseId: savedComment.courseId,
      userId: savedComment.userId,
      parentId: savedComment.parentId,
      replyToCommentId: savedComment.replyToCommentId,
      content: savedComment.content,
      createdAt: savedComment.createdAt,
      user: {
        id: savedComment.user.id,
        nickname: savedComment.user.nickname,
        avatar: savedComment.user.avatar,
        isVip: savedComment.user.isVip,
      },
      replyToUser: savedComment.replyToComment ? {
        id: savedComment.replyToComment.user.id,
        nickname: savedComment.replyToComment.user.nickname,
      } : undefined
    };
  }

  async getCourseAccess(userId: number, courseId: number) {
    const userCourse = await this.userCourseRepository.findOne({
      where: { userId, courseId },
      relations: ['course'],
    });

    if (!userCourse) {
      throw new ForbiddenException('You have not purchased this course');
    }

    if (userCourse.expiredAt < new Date()) {
      throw new ForbiddenException('Your access to this course has expired');
    }

    return {
      hasAccess: true,
      driveLink: userCourse.course.driveLink, // In a real app, this should be a dynamic signed URL
      expiredAt: userCourse.expiredAt,
    };
  }
}