package storagex

import (
	"fmt"
	"sync"
)

// DriverFactory 驱动工厂接口
type DriverFactory interface {
	Create(cfg Config) (Uploader, error)
}

// Registry 注册中心，单例模式管理所有上传通道
type Registry struct {
	mu        sync.RWMutex
	factories map[string]DriverFactory // 存储服务商工厂 (aliyun -> AliyunFactory)
	clients   map[string]Uploader      // 缓存具体的客户端实例 (key = provider:accountID)
}

// 全局注册中心实例
var globalRegistry = &Registry{
	factories: make(map[string]DriverFactory),
	clients:   make(map[string]Uploader),
}

// Register 注册服务商工厂
// 例如: Register("aliyun", &AliyunFactory{})
func Register(provider string, factory DriverFactory) {
	globalRegistry.mu.Lock()
	defer globalRegistry.mu.Unlock()
	globalRegistry.factories[provider] = factory
}

// GetUploader 获取指定服务商和账号的上传器
// 如果该账号的客户端已存在则复用，不存在则创建
func GetUploader(provider, accountID string, cfg Config) (Uploader, error) {
	key := fmt.Sprintf("%s:%s", provider, accountID)

	// 1. 尝试从缓存获取 (读锁)
	globalRegistry.mu.RLock()
	client, ok := globalRegistry.clients[key]
	globalRegistry.mu.RUnlock()

	if ok {
		return client, nil
	}

	// 2. 缓存未命中，需要创建 (写锁)
	globalRegistry.mu.Lock()
	defer globalRegistry.mu.Unlock()

	// 双重检查锁，防止并发下重复创建
	if client, ok := globalRegistry.clients[key]; ok {
		return client, nil
	}

	factory, ok := globalRegistry.factories[provider]
	if !ok {
		return nil, fmt.Errorf("unknown provider: %s", provider)
	}

	// 创建新的 Uploader 实例
	client, err := factory.Create(cfg)
	if err != nil {
		return nil, fmt.Errorf("failed to create uploader for %s: %w", provider, err)
	}

	// 存入缓存
	globalRegistry.clients[key] = client
	return client, nil
}

// Clear 主要用于测试，清空缓存
func Clear() {
	globalRegistry.mu.Lock()
	defer globalRegistry.mu.Unlock()
	globalRegistry.clients = make(map[string]Uploader)
}