import { Injectable, Logger, NotFoundException } from '@nestjs/common';
import { Types } from 'mongoose';
import { FeedVersionService } from '../../infrastructure/cache/feed-version.service';
import { NotificationsService } from '../notifications/notifications.service';
import { CommentsRepository } from '../comments/comments.repository';
import { PostsRepository } from '../posts/posts.repository';
import { LikesRepository } from './likes.repository';
import { ToggleLikeDto } from './dto/toggle-like.dto';

@Injectable()
export class LikesService {
  private readonly logger = new Logger(LikesService.name);

  constructor(
    private readonly likesRepository: LikesRepository,
    private readonly postsRepository: PostsRepository,
    private readonly commentsRepository: CommentsRepository,
    private readonly feedVersionService: FeedVersionService,
    private readonly notificationsService: NotificationsService,
  ) {}

  async toggle(userId: string, dto: ToggleLikeDto): Promise<{ liked: boolean; targetId: string; targetType: string }> {
    const existing = await this.likesRepository.findOne(userId, dto.targetId, dto.targetType);
    return existing ? this.unlike(userId, dto) : this.like(userId, dto);
  }

  async like(userId: string, dto: ToggleLikeDto): Promise<{ liked: boolean; targetId: string; targetType: string }> {
    await this.assertTargetExists(dto);
    const notificationContext = await this.resolveNotificationContext(dto);

    const existing = await this.likesRepository.findOne(userId, dto.targetId, dto.targetType);
    if (existing) {
      return { liked: true, targetId: dto.targetId, targetType: dto.targetType };
    }

    await this.likesRepository.create(userId, dto.targetId, dto.targetType);
    if (dto.targetType === 'post') {
      await this.postsRepository.incrementLikesCount(dto.targetId, 1);
    }
    await this.feedVersionService.bumpGlobalVersion();
    if (notificationContext.recipientId && notificationContext.recipientId !== userId) {
      try {
        await this.notificationsService.createLikeNotification(
          userId,
          notificationContext.recipientId,
          dto.targetId,
          {
            resourceType: dto.targetType,
            previewText: notificationContext.previewText,
          },
        );
      } catch (error) {
        this.logger.warn(
          `Like notification failed for actor=${userId} recipient=${notificationContext.recipientId}: ${
            error instanceof Error ? error.message : 'unknown error'
          }`,
        );
      }
    }

    return { liked: true, targetId: dto.targetId, targetType: dto.targetType };
  }

  async unlike(userId: string, dto: ToggleLikeDto): Promise<{ liked: boolean; targetId: string; targetType: string }> {
    await this.assertTargetExists(dto);

    const existing = await this.likesRepository.findOne(userId, dto.targetId, dto.targetType);
    if (!existing) {
      return { liked: false, targetId: dto.targetId, targetType: dto.targetType };
    }

    await this.likesRepository.deleteById(existing.id);
    if (dto.targetType === 'post') {
      await this.postsRepository.incrementLikesCount(dto.targetId, -1);
    }
    await this.feedVersionService.bumpGlobalVersion();

    return { liked: false, targetId: dto.targetId, targetType: dto.targetType };
  }

  async getStatus(userId: string, dto: ToggleLikeDto): Promise<{ liked: boolean; targetId: string; targetType: string }> {
    const targetExists = await this.targetExists(dto);
    if (!targetExists) {
      return { liked: false, targetId: dto.targetId, targetType: dto.targetType };
    }

    const existing = await this.likesRepository.findOne(userId, dto.targetId, dto.targetType);
    return { liked: !!existing, targetId: dto.targetId, targetType: dto.targetType };
  }

  private async assertTargetExists(dto: ToggleLikeDto): Promise<void> {
    const targetExists = await this.targetExists(dto);
    if (!targetExists) {
      throw new NotFoundException(dto.targetType === 'post' ? 'Post not found' : 'Comment not found');
    }
  }

  private async targetExists(dto: ToggleLikeDto): Promise<boolean> {
    if (dto.targetType === 'post') {
      const post = await this.postsRepository.findById(dto.targetId);
      return !!post;
    }

    const comment = await this.commentsRepository.findById(dto.targetId);
    return !!comment;
  }

  private async resolveNotificationContext(
    dto: ToggleLikeDto,
  ): Promise<{ recipientId: string; previewText: string }> {
    if (dto.targetType === 'post') {
      const post = await this.postsRepository.findById(dto.targetId);
      return {
        recipientId: this.extractEntityId(post?.authorId),
        previewText: (post?.content ?? '').slice(0, 140),
      };
    }

    const comment = await this.commentsRepository.findById(dto.targetId);
    return {
      recipientId: comment?.authorId?.toString?.() ?? '',
      previewText: (comment?.content ?? '').slice(0, 140),
    };
  }

  private extractEntityId(value: unknown): string {
    if (!value) {
      return '';
    }

    if (typeof value === 'string') {
      return value;
    }

    if (value instanceof Types.ObjectId) {
      return value.toString();
    }

    if (typeof value === 'object') {
      const candidate = value as { _id?: unknown; id?: unknown };
      if (candidate._id instanceof Types.ObjectId) {
        return candidate._id.toString();
      }
      if (typeof candidate._id === 'string') {
        return candidate._id;
      }
      if (typeof candidate.id === 'string') {
        return candidate.id;
      }
    }

    return '';
  }
}