import { Injectable } from '@nestjs/common';
import { Comment } from '../../domain/entities/comment.entity.js';
import { CommentDto } from '../dto/comment.dto.js';
import { CommentApplicationMapper } from '../mappers/comment-application.mapper.js';
import { GetUsersUseCase } from '../../../user/application/use-cases/get-users/get-users.use-case.js';
import { GetUsersQuery } from '../../../user/application/use-cases/get-users/get-users.query.js';
import { GetFilesUseCase } from '../../../file/application/use-cases/get-files/get-files.use-case.js';
import { GetFilesQuery } from '../../../file/application/use-cases/get-files/get-files.query.js';

/** Раскрывает автора и вложения комментария (или списка комментариев) */
@Injectable()
export class CommentExpanderService {
  constructor(
    private readonly getUsersUseCase: GetUsersUseCase,
    private readonly getFilesUseCase: GetFilesUseCase,
  ) {}

  async expand(comment: Comment): Promise<CommentDto> {
    const [dto] = await this.expandAll([comment]);
    return dto!;
  }

  async expandAll(comments: Comment[]): Promise<CommentDto[]> {
    if (comments.length === 0) return [];

    const userIds = [...new Set(comments.map((comment) => comment.authorId).filter((id): id is string => Boolean(id)))];
    const fileIds = comments.flatMap((comment) => comment.fileIds);

    const [users, files] = await Promise.all([
      userIds.length > 0 ? this.getUsersUseCase.execute(new GetUsersQuery(userIds)) : [],
      fileIds.length > 0 ? this.getFilesUseCase.execute(new GetFilesQuery(fileIds)) : [],
    ]);
    const usersById = new Map(users.map((user) => [user.id, user]));
    const filesById = new Map(files.map((file) => [file.id, file]));

    return comments.map((comment) => CommentApplicationMapper.toDto(comment, usersById, filesById));
  }
}