package service

import (
	"errors"

	"gorm.io/gorm"

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

// FollowUser 关注某人（幂等；不能关注自己）
func (s *Service) FollowUser(followerID, followeeID string) error {
	if followerID == "" || followeeID == "" {
		return errors.New("参数不完整")
	}
	if followerID == followeeID {
		return errors.New("不能关注自己")
	}
	var u model.User
	if err := s.db.Select("id").First(&u, "id = ?", followeeID).Error; err != nil {
		return ErrNotFound
	}
	f := model.Follow{FollowerID: followerID, FolloweeID: followeeID}
	return s.db.Where("follower_id = ? AND followee_id = ?", followerID, followeeID).
		FirstOrCreate(&f).Error
}

// UnfollowUser 取消关注（幂等）
func (s *Service) UnfollowUser(followerID, followeeID string) error {
	return s.db.Where("follower_id = ? AND followee_id = ?", followerID, followeeID).
		Delete(&model.Follow{}).Error
}

// followeeIDs 我关注的所有人
func (s *Service) followeeIDs(userID string) []string {
	var ids []string
	s.db.Model(&model.Follow{}).Where("follower_id = ?", userID).Pluck("followee_id", &ids)
	return ids
}

// markFollowed 标记帖子作者是否已被我关注（用于前端显示「关注」按钮）
func (s *Service) markFollowed(userID string, posts []model.Post) {
	if userID == "" || len(posts) == 0 {
		return
	}
	authors := make([]string, 0, len(posts))
	for i := range posts {
		if posts[i].UserID != "" && posts[i].UserID != userID {
			authors = append(authors, posts[i].UserID)
		}
	}
	if len(authors) == 0 {
		return
	}
	var followed []string
	s.db.Model(&model.Follow{}).
		Where("follower_id = ? AND followee_id IN ?", userID, authors).
		Pluck("followee_id", &followed)
	set := make(map[string]bool, len(followed))
	for _, id := range followed {
		set[id] = true
	}
	for i := range posts {
		posts[i].IsSelf = posts[i].UserID == userID
		posts[i].Followed = set[posts[i].UserID]
	}
}

// ensureNotFound 供 handler 区分错误类型
var _ = gorm.ErrRecordNotFound