package service

import (
	"encoding/json"

	"gorm.io/datatypes"
	"gorm.io/gorm"

	"github.com/sundynix/pets-be/internal/model"
)

// attachPostImages 把帖子的 ImageFileIDs 解析为可展示的 Images（URL 数组）。
// 机器人帖 ImageFileIDs 为空，保留其 Images（emoji）不变。
func (s *Service) attachPostImages(posts []model.Post) {
	perPost := make([][]string, len(posts))
	all := []string{}
	for i := range posts {
		if len(posts[i].ImageFileIDs) == 0 {
			continue
		}
		var ids []string
		if json.Unmarshal(posts[i].ImageFileIDs, &ids) == nil && len(ids) > 0 {
			perPost[i] = ids
			all = append(all, ids...)
		}
	}
	if len(all) == 0 {
		return
	}
	urlMap := s.fileURLs(all)
	for i := range posts {
		if len(perPost[i]) == 0 {
			continue
		}
		urls := make([]string, 0, len(perPost[i]))
		for _, id := range perPost[i] {
			if u := urlMap[id]; u != "" {
				urls = append(urls, u)
			}
		}
		if b, err := json.Marshal(urls); err == nil {
			posts[i].Images = datatypes.JSON(b)
		}
	}
}

// tabTag 将 feed tab 映射为标签过滤（空表示不过滤）
func tabTag(tab string) string {
	switch tab {
	case "新手求助":
		return "求助"
	case "晒宠":
		return "晒宠"
	case "经验":
		return "经验"
	default: // 推荐 / 关注
		return ""
	}
}

// ListPosts 帖子分页列表
func (s *Service) ListPosts(tab string, offset, limit int) ([]model.Post, int64, error) {
	q := s.db.Model(&model.Post{}).Where("status = ?", model.PostPublished)
	if tag := tabTag(tab); tag != "" {
		q = q.Where("JSON_CONTAINS(tags, ?)", `"`+tag+`"`)
	}
	var total int64
	if err := q.Count(&total).Error; err != nil {
		return nil, 0, err
	}
	var posts []model.Post
	if err := q.Order("id desc").Offset(offset).Limit(limit).Find(&posts).Error; err != nil {
		return nil, 0, err
	}
	s.attachPostImages(posts)
	return posts, total, nil
}

// GetPost 帖子详情
func (s *Service) GetPost(postID string) (*model.Post, error) {
	var p model.Post
	if err := s.db.First(&p, postID).Error; err != nil {
		if err == gorm.ErrRecordNotFound {
			return nil, ErrNotFound
		}
		return nil, err
	}
	one := []model.Post{p}
	s.attachPostImages(one)
	return &one[0], nil
}

// PostInput 发帖入参
type PostInput struct {
	PetID        *string
	Identity     string
	Content      string
	Tags         datatypes.JSON
	Images       datatypes.JSON
	ImageFileIDs datatypes.JSON
}

// CreatePost 发帖
func (s *Service) CreatePost(userID string, in PostInput) (*model.Post, error) {
	authorName := "匿名宠友"
	authorEmoji := "🐾"
	switch in.Identity {
	case "official":
		authorName = "肉垫计划官方"
	case "petName":
		if in.PetID != nil {
			var pet model.Pet
			if err := s.db.First(&pet, *in.PetID).Error; err == nil {
				authorName = pet.Name + "的铲屎官"
				authorEmoji = pet.Emoji
			}
		}
	}
	p := model.Post{
		UserID: userID, PetID: in.PetID, AuthorName: authorName, AuthorEmoji: authorEmoji,
		Identity: in.Identity, Content: in.Content, Tags: in.Tags, Images: in.Images,
		ImageFileIDs: in.ImageFileIDs, Status: model.PostPublished,
	}
	if err := s.db.Create(&p).Error; err != nil {
		return nil, err
	}
	one := []model.Post{p}
	s.attachPostImages(one)
	return &one[0], nil
}

// LikePost 点赞（幂等：已赞则不重复计数）
func (s *Service) LikePost(userID, postID string) (int, error) {
	if _, err := s.GetPost(postID); err != nil {
		return 0, err
	}
	err := s.db.Transaction(func(tx *gorm.DB) error {
		like := model.PostLike{PostID: postID, UserID: userID}
		res := tx.Where("post_id = ? AND user_id = ?", postID, userID).FirstOrCreate(&like)
		if res.Error != nil {
			return res.Error
		}
		if res.RowsAffected == 1 { // 新建才计数
			return tx.Model(&model.Post{}).Where("id = ?", postID).
				UpdateColumn("like_count", gorm.Expr("like_count + 1")).Error
		}
		return nil
	})
	if err != nil {
		return 0, err
	}
	return s.postLikeCount(postID)
}

// UnlikePost 取消点赞
func (s *Service) UnlikePost(userID, postID string) (int, error) {
	if _, err := s.GetPost(postID); err != nil {
		return 0, err
	}
	err := s.db.Transaction(func(tx *gorm.DB) error {
		res := tx.Where("post_id = ? AND user_id = ?", postID, userID).Delete(&model.PostLike{})
		if res.Error != nil {
			return res.Error
		}
		if res.RowsAffected == 1 {
			return tx.Model(&model.Post{}).Where("id = ? AND like_count > 0", postID).
				UpdateColumn("like_count", gorm.Expr("like_count - 1")).Error
		}
		return nil
	})
	if err != nil {
		return 0, err
	}
	return s.postLikeCount(postID)
}

func (s *Service) postLikeCount(postID string) (int, error) {
	var p model.Post
	if err := s.db.Select("like_count").First(&p, postID).Error; err != nil {
		return 0, err
	}
	return p.LikeCount, nil
}

// ListComments 评论分页
func (s *Service) ListComments(postID string, offset, limit int) ([]model.Comment, int64, error) {
	q := s.db.Model(&model.Comment{}).Where("post_id = ? AND status = ?", postID, "published")
	var total int64
	if err := q.Count(&total).Error; err != nil {
		return nil, 0, err
	}
	var comments []model.Comment
	if err := q.Order("id desc").Offset(offset).Limit(limit).Find(&comments).Error; err != nil {
		return nil, 0, err
	}
	return comments, total, nil
}

// CreateComment 评论
func (s *Service) CreateComment(userID, postID string, content string) (*model.Comment, error) {
	if _, err := s.GetPost(postID); err != nil {
		return nil, err
	}
	var user model.User
	name := "宠友"
	if err := s.db.First(&user, userID).Error; err == nil && user.Nickname != "" {
		name = user.Nickname
	}
	comment := model.Comment{PostID: postID, UserID: userID, AuthorName: name, Content: content, Status: "published"}
	if err := s.db.Transaction(func(tx *gorm.DB) error {
		if err := tx.Create(&comment).Error; err != nil {
			return err
		}
		return tx.Model(&model.Post{}).Where("id = ?", postID).
			UpdateColumn("comment_count", gorm.Expr("comment_count + 1")).Error
	}); err != nil {
		return nil, err
	}
	return &comment, nil
}