backend/internal/repository/vote_repo.go

package repository

import (
	"errors"
	"with_you/internal/model"

	"gorm.io/gorm"
)

// VoteRepository 投票仓储接口
type VoteRepository interface {
	CreateOptions(postID string, options []string) error
	GetOptionsByPostID(postID string) ([]model.VoteOption, error)
	Vote(postID, userID, optionID string) error
	Unvote(postID, userID string) error
	GetUserVote(postID, userID string) (*model.UserVote, error)
	UpdateOption(optionID, content string) error
	DeleteOptionsByPostID(postID string) error
	CountVotesByOption(postID, optionID string) (int, error)
}

// voteRepository 投票仓储实现
type voteRepository struct {
	db *gorm.DB
}

// NewVoteRepository 创建投票仓储
func NewVoteRepository(db *gorm.DB) VoteRepository {
	return &voteRepository{db: db}
}

// CreateOptions 批量创建投票选项（使用批量插入，避免 N+1 问题）
func (r *voteRepository) CreateOptions(postID string, options []string) error {
	if len(options) == 0 {
		return nil
	}

	// 构建批量插入的选项切片
	voteOptions := make([]model.VoteOption, len(options))
	for i, content := range options {
		voteOptions[i] = model.VoteOption{
			PostID:    postID,
			Content:   content,
			SortOrder: i,
		}
	}

	// 使用 GORM 的 Create 方法批量插入
	return r.db.CreateInBatches(voteOptions, 100).Error
}

// GetOptionsByPostID 获取帖子的所有投票选项
func (r *voteRepository) GetOptionsByPostID(postID string) ([]model.VoteOption, error) {
	var options []model.VoteOption
	err := r.db.Where("post_id = ?", postID).Order("sort_order ASC").Find(&options).Error
	return options, err
}

// Vote 用户投票
func (r *voteRepository) Vote(postID, userID, optionID string) error {
	return r.db.Transaction(func(tx *gorm.DB) error {
		// 检查用户是否已投票
		var existing model.UserVote
		err := tx.Where("post_id = ? AND user_id = ?", postID, userID).First(&existing).Error
		if err == nil {
			// 已经投票，返回错误
			return errors.New("user already voted")
		}
		if err != gorm.ErrRecordNotFound {
			return err
		}

		// 验证选项是否属于该帖子
		var option model.VoteOption
		if err := tx.Where("id = ? AND post_id = ?", optionID, postID).First(&option).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				return errors.New("invalid option")
			}
			return err
		}

		// 创建投票记录
		if err := tx.Create(&model.UserVote{
			PostID:   postID,
			UserID:   userID,
			OptionID: optionID,
		}).Error; err != nil {
			return err
		}

		// 原子增加选项投票数
		return tx.Model(&model.VoteOption{}).Where("id = ?", optionID).
			UpdateColumn("votes_count", gorm.Expr("votes_count + 1")).Error
	})
}

// Unvote 取消投票
func (r *voteRepository) Unvote(postID, userID string) error {
	return r.db.Transaction(func(tx *gorm.DB) error {
		// 获取用户的投票记录
		var userVote model.UserVote
		err := tx.Where("post_id = ? AND user_id = ?", postID, userID).First(&userVote).Error
		if err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				return nil // 没有投票记录，直接返回
			}
			return err
		}

		// 删除投票记录
		result := tx.Where("post_id = ? AND user_id = ?", postID, userID).Delete(&model.UserVote{})
		if result.Error != nil {
			return result.Error
		}

		if result.RowsAffected > 0 {
			// 原子减少选项投票数
			return tx.Model(&model.VoteOption{}).Where("id = ?", userVote.OptionID).
				UpdateColumn("votes_count", gorm.Expr("votes_count - 1")).Error
		}

		return nil
	})
}

// GetUserVote 获取用户在指定帖子的投票
func (r *voteRepository) GetUserVote(postID, userID string) (*model.UserVote, error) {
	var userVote model.UserVote
	err := r.db.Where("post_id = ? AND user_id = ?", postID, userID).First(&userVote).Error
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, nil
		}
		return nil, err
	}
	return &userVote, nil
}

// UpdateOption 更新选项内容
func (r *voteRepository) UpdateOption(optionID, content string) error {
	return r.db.Model(&model.VoteOption{}).Where("id = ?", optionID).
		Update("content", content).Error
}

// DeleteOptionsByPostID 删除帖子的所有投票选项
func (r *voteRepository) DeleteOptionsByPostID(postID string) error {
	return r.db.Transaction(func(tx *gorm.DB) error {
		if err := tx.Where("post_id = ?", postID).Delete(&model.UserVote{}).Error; err != nil {
			return err
		}
		return tx.Where("post_id = ?", postID).Delete(&model.VoteOption{}).Error
	})
}

// CountVotesByOption 统计指定选项的投票数
func (r *voteRepository) CountVotesByOption(postID, optionID string) (int, error) {
	var count int64
	err := r.db.Model(&model.UserVote{}).Where("post_id = ? AND option_id = ?", postID, optionID).Count(&count).Error
	return int(count), err
}