package repository

import (
	"errors"

	"gorm.io/gorm"
)

// IsNotFound 检查是否为记录未找到错误
func IsNotFound(err error) bool {
	return errors.Is(err, gorm.ErrRecordNotFound)
}

// HandleNotFound 处理记录未找到的情况，未找到时返回 nil, nil
func HandleNotFound[T any](result *T, err error) (*T, error) {
	if err != nil {
		if IsNotFound(err) {
			return nil, nil
		}
		return nil, err
	}
	return result, nil
}

// Paginate 创建分页查询
func Paginate(page, pageSize int) func(db *gorm.DB) *gorm.DB {
	return func(db *gorm.DB) *gorm.DB {
		if page < 1 {
			page = 1
		}
		if pageSize < 1 {
			pageSize = 20
		}
		if pageSize > 100 {
			pageSize = 100
		}
		offset := (page - 1) * pageSize
		return db.Offset(offset).Limit(pageSize)
	}
}

// PaginatedQuery 执行分页查询，返回列表和总数
func PaginatedQuery[T any](
	baseQuery *gorm.DB,
	page, pageSize int,
	orderBy string,
	preloads ...string,
) ([]T, int64, error) {
	var items []T
	var total int64

	// 获取总数
	if err := baseQuery.Count(&total).Error; err != nil {
		return nil, 0, err
	}

	// 分页查询
	query := baseQuery.Scopes(Paginate(page, pageSize))

	// 添加排序
	if orderBy != "" {
		query = query.Order(orderBy)
	}

	// 添加预加载
	for _, preload := range preloads {
		query = query.Preload(preload)
	}

	if err := query.Find(&items).Error; err != nil {
		return nil, 0, err
	}

	return items, total, nil
}