package nju.seec.helper.service.impl;

import nju.seec.helper.dao.CommentDAO;
import nju.seec.helper.dao.SlideDAO;
import nju.seec.helper.dao.UserDAO;
import nju.seec.helper.dto.CommentDTO;
import nju.seec.helper.dto.LoginUser;
import nju.seec.helper.entity.Comment;
import nju.seec.helper.entity.Slide;
import nju.seec.helper.service.CommentService;
import nju.seec.helper.service.MessageService;
import nju.seec.helper.service.util.AuthUtils;
import nju.seec.helper.util.enums.MessageType;
import nju.seec.helper.vo.CommentVO;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.Collections;
import java.util.stream.Collectors;

/**
 * @author cst
 */
@Service
public class CommentServiceImpl implements CommentService {
    private final CommentDAO commentDAO;
    private final SlideDAO slideDAO;
    private final UserDAO userDAO;

    private final MessageService messageService;

    public CommentServiceImpl(CommentDAO commentDAO, SlideDAO slideDAO, UserDAO userDAO, MessageService messageService) {
        this.commentDAO = commentDAO;
        this.slideDAO = slideDAO;
        this.userDAO = userDAO;
        this.messageService = messageService;
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public CommentVO createComment(LoginUser user, CommentDTO commentDTO) {
        Comment comment = new Comment()
                .setSlideId(commentDTO.getSlideId())
                .setPageNumber(commentDTO.getPageNumber())
                .setUser(userDAO.findUserById(user.getId()))
                .setTitle(commentDTO.getTitle())
                .setContent(commentDTO.getContent());
        comment = commentDAO.save(comment);

        // 增加通知
        Slide slide = slideDAO.findSlideById(comment.getSlideId());
        if (!user.getId().equals(slide.getTeacher().getId())) {
            messageService.createMessage(Collections.singleton(slide.getTeacher().getId()), MessageType.COMMENT_NEW, String.format("课程 [%s] 的课件 [%s] 在第%d页有新评论", slide.getCourse().getName(), slide.getName(), comment.getPageNumber()), slide.getId());
        }

        return new CommentVO(comment);
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void removeComment(LoginUser user, Long commentId) {
        Comment comment = commentDAO.findCommentById(commentId);

        AuthUtils.checkDataAuth(user.getId(), comment.getUser().getId(), "您无权删除该评论");

        unTopComment(comment);
        commentDAO.deleteById(commentId);
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void topComment(LoginUser user, Long commentId) {
        Comment comment = commentDAO.findCommentById(commentId);

        AuthUtils.checkDataAuth(user.getId(), slideDAO.findSlideById(comment.getSlideId()).getTeacher().getId(), "您无权在该评论区置顶评论");

        unTopComment(comment);
        comment.setTopNumber((int) countTopComments(comment.getSlideId(), comment.getPageNumber()) + 1);
        commentDAO.save(comment);
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void unTopComment(LoginUser user, Long commentId) {
        Comment comment = commentDAO.findCommentById(commentId);

        AuthUtils.checkDataAuth(user.getId(), slideDAO.findSlideById(comment.getSlideId()).getTeacher().getId(), "您无权在该评论区取消置顶评论");

        unTopComment(comment);
        commentDAO.save(comment);
    }

    @Transactional(readOnly = true)
    @Override
    public Page<CommentVO> getCommentsBySlideAndPageNumber(Long slideId, Integer pageNumber, Pageable pageable) {
        return findBySlideIdAndPageNumber(slideId, pageNumber, pageable).map(CommentVO::new);
    }

    @Transactional(readOnly = true)
    @Override
    public CommentVO getOneComment(Long commentId) {
        return new CommentVO(commentDAO.findCommentById(commentId));
    }

    private void unTopComment(Comment comment) {
        Integer topNumber = comment.getTopNumber();
        comment.setTopNumber(0);
        decTopNumber(comment.getSlideId(), comment.getPageNumber(), topNumber);
    }

    long countTopComments(Long slideId, Integer pageNumber) {
        return commentDAO.count(
                (Specification<Comment>) (root, query, cb) -> cb.and(
                        cb.equal(root.get("slideId"), slideId),
                        cb.equal(root.get("pageNumber"), pageNumber),
                        cb.notEqual(root.get("topNumber"), 0)));
    }

    Page<Comment> findBySlideIdAndPageNumber(Long slideId, Integer pageNumber, Pageable pageable) {
        return commentDAO.findAll(
                (Specification<Comment>) (root, query, cb) -> cb.and(
                        cb.equal(root.get("slideId"), slideId),
                        cb.equal(root.get("pageNumber"), pageNumber)),
                pageable);
    }

    void decTopNumber(Long slideId, Integer pageNumber, Integer topNumber) {
        commentDAO.saveAll(
                commentDAO
                        .findAll((Specification<Comment>) (root, query, cb) -> cb.and(
                                cb.equal(root.get("slideId"), slideId),
                                cb.equal(root.get("pageNumber"), pageNumber),
                                cb.gt(root.get("topNumber"), topNumber)))
                        .parallelStream()
                        .peek(comment -> comment.setTopNumber(comment.getTopNumber() - 1))
                        .collect(Collectors.toSet()));
    }
}