package provider

import (
	"applet/app/db"
	"code.fnuoos.com/EggPlanet/egg_models.git/src/implement"
	"code.fnuoos.com/EggPlanet/egg_models.git/src/model"
	"encoding/json"
	"fmt"
	"sync"
)

var (
	instance *userInfoProvider //userInfoProvider 的单例实例
	once     sync.Once
)

// UserInfoProvider 定义了一个接口来管理用户信息的获取
type UserInfoProvider interface {
	GetUserInfo(uid int64) (*model.User, error)
}

// userInfoProvider 实现了 UserInfoProvider 接口
type userInfoProvider struct {
	userCache map[int64]string
	mu        sync.RWMutex
}

// GetUserInfoProvider 返回 userInfoProvider 的单例实例
func GetUserInfoProvider() UserInfoProvider {
	once.Do(func() {
		instance = &userInfoProvider{
			userCache: make(map[int64]string),
		}
	})
	return instance
}

// GetUserInfo 根据用户名返回用户信息(TODO::支持多个goroutine并发执行)
func (p *userInfoProvider) GetUserInfo(uid int64) (*model.User, error) {
	p.mu.RLock() //上"读"锁
	userStr, exists := p.userCache[uid]
	p.mu.RUnlock() //放"读"锁

	var userModel *model.User
	if exists {
		err := json.Unmarshal([]byte(userStr), &userModel)
		if err != nil {
			return nil, fmt.Errorf("failed to unmarshal user info: %w", err)
		}
		return userModel, nil
	}

	// 如果内存缓存中没有，则从 数据库查询
	newUserDb := implement.NewUserDb(db.Db)
	userModel, err := newUserDb.UserGetOneByParams(map[string]interface{}{
		"key":   "id",
		"value": uid,
	})
	if err != nil {
		return userModel, err
	}

	// 缓存到内存中
	p.mu.Lock() //上"写"锁
	p.userCache[uid] = string(userStr)
	p.mu.Unlock() //放"写"锁

	return userModel, nil
}