# 中间件文档

## 概述

中间件层是 UdminAI 系统的核心组件，基于 Axum 框架实现，提供了认证授权、请求日志、错误处理、CORS、WebSocket 支持、SSE（Server-Sent Events）等功能。中间件采用洋葱模型，按顺序处理请求和响应。

## 架构设计

### 中间件模块结构

```
middlewares/
├── mod.rs                    # 中间件模块导出
├── auth.rs                   # 认证中间件
├── cors.rs                   # CORS 中间件
├── http_client.rs            # HTTP 客户端中间件
├── logging.rs                # 请求日志中间件
├── rate_limit.rs             # 限流中间件
├── sse.rs                    # Server-Sent Events 中间件
└── ws.rs                     # WebSocket 中间件
```

### 设计原则

- **模块化**: 每个中间件独立实现，职责单一
- **可组合**: 中间件可以灵活组合使用
- **高性能**: 最小化性能开销
- **类型安全**: 利用 Rust 类型系统确保安全
- **可配置**: 支持灵活的配置选项
- **可测试**: 易于单元测试和集成测试

## 认证中间件 (auth.rs)

### 功能特性

- JWT Token 验证
- 用户身份识别
- 权限检查
- Token 刷新机制
- 多种认证策略

### 实现代码

```rust
use axum::{
    extract::{Request, State},
    http::{header, StatusCode},
    middleware::Next,
    response::Response,
};
use jsonwebtoken::{decode, DecodingKey, Validation};
use serde::{Deserialize, Serialize};
use std::collections::HashSet;
use tracing::{error, info, warn};

use crate::{
    error::AppError,
    models::user,
    services::user_service,
    AppState,
};

/// JWT Claims 结构
#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct Claims {
    pub sub: String,        // 用户ID
    pub username: String,   // 用户名
    pub roles: Vec<String>, // 角色列表
    pub permissions: Vec<String>, // 权限列表
    pub exp: usize,         // 过期时间
    pub iat: usize,         // 签发时间
    pub iss: String,        // 签发者
}

/// 认证上下文
#[derive(Debug, Clone)]
pub struct AuthContext {
    pub user_id: String,
    pub username: String,
    pub roles: Vec<String>,
    pub permissions: HashSet<String>,
}

/// JWT 认证中间件
pub async fn jwt_auth_middleware(
    State(state): State<AppState>,
    mut request: Request,
    next: Next,
) -> Result<Response, AppError> {
    let auth_header = request
        .headers()
        .get(header::AUTHORIZATION)
        .and_then(|header| header.to_str().ok());

    let token = match auth_header {
        Some(header) if header.starts_with("Bearer ") => {
            header.trim_start_matches("Bearer ")
        }
        _ => {
            warn!(target = "udmin", "Missing or invalid authorization header");
            return Err(AppError::Unauthorized("缺少认证令牌".to_string()));
        }
    };

    // 验证 JWT Token
    let claims = match decode::<Claims>(
        token,
        &DecodingKey::from_secret(state.config.jwt_secret.as_ref()),
        &Validation::default(),
    ) {
        Ok(token_data) => token_data.claims,
        Err(err) => {
            error!(target = "udmin", error = %err, "JWT token validation failed");
            return Err(AppError::Unauthorized("无效的认证令牌".to_string()));
        }
    };

    // 检查用户是否存在且活跃
    let user = user_service::find_by_id(&state.db, &claims.sub)
        .await
        .map_err(|_| AppError::Unauthorized("用户不存在".to_string()))?;

    if user.status != user::UserStatus::Active {
        warn!(target = "udmin", user_id = %claims.sub, "Inactive user attempted access");
        return Err(AppError::Unauthorized("用户账户已被禁用".to_string()));
    }

    // 创建认证上下文
    let auth_context = AuthContext {
        user_id: claims.sub.clone(),
        username: claims.username.clone(),
        roles: claims.roles.clone(),
        permissions: claims.permissions.into_iter().collect(),
    };

    // 将认证上下文添加到请求扩展中
    request.extensions_mut().insert(auth_context);

    info!(
        target = "udmin",
        user_id = %claims.sub,
        username = %claims.username,
        "User authenticated successfully"
    );

    Ok(next.run(request).await)
}

/// 权限检查中间件
pub fn require_permission(required_permission: &'static str) -> impl Fn(Request, Next) -> std::pin::Pin<Box<dyn std::future::Future<Output = Result<Response, AppError>> + Send>> + Clone {
    move |request: Request, next: Next| {
        Box::pin(async move {
            let auth_context = request
                .extensions()
                .get::<AuthContext>()
                .ok_or_else(|| AppError::Unauthorized("未认证的请求".to_string()))?;

            if !auth_context.permissions.contains(required_permission) {
                warn!(
                    target = "udmin",
                    user_id = %auth_context.user_id,
                    required_permission = %required_permission,
                    "Permission denied"
                );
                return Err(AppError::Forbidden("权限不足".to_string()));
            }

            info!(
                target = "udmin",
                user_id = %auth_context.user_id,
                permission = %required_permission,
                "Permission granted"
            );

            Ok(next.run(request).await)
        })
    }
}

/// 角色检查中间件
pub fn require_role(required_role: &'static str) -> impl Fn(Request, Next) -> std::pin::Pin<Box<dyn std::future::Future<Output = Result<Response, AppError>> + Send>> + Clone {
    move |request: Request, next: Next| {
        Box::pin(async move {
            let auth_context = request
                .extensions()
                .get::<AuthContext>()
                .ok_or_else(|| AppError::Unauthorized("未认证的请求".to_string()))?;

            if !auth_context.roles.contains(&required_role.to_string()) {
                warn!(
                    target = "udmin",
                    user_id = %auth_context.user_id,
                    required_role = %required_role,
                    "Role check failed"
                );
                return Err(AppError::Forbidden("角色权限不足".to_string()));
            }

            info!(
                target = "udmin",
                user_id = %auth_context.user_id,
                role = %required_role,
                "Role check passed"
            );

            Ok(next.run(request).await)
        })
    }
}

/// 可选认证中间件（不强制要求认证）
pub async fn optional_auth_middleware(
    State(state): State<AppState>,
    mut request: Request,
    next: Next,
) -> Response {
    let auth_header = request
        .headers()
        .get(header::AUTHORIZATION)
        .and_then(|header| header.to_str().ok());

    if let Some(header) = auth_header {
        if let Some(token) = header.strip_prefix("Bearer ") {
            if let Ok(token_data) = decode::<Claims>(
                token,
                &DecodingKey::from_secret(state.config.jwt_secret.as_ref()),
                &Validation::default(),
            ) {
                let claims = token_data.claims;
                
                // 创建认证上下文
                let auth_context = AuthContext {
                    user_id: claims.sub.clone(),
                    username: claims.username.clone(),
                    roles: claims.roles.clone(),
                    permissions: claims.permissions.into_iter().collect(),
                };

                request.extensions_mut().insert(auth_context);
            }
        }
    }

    next.run(request).await
}
```

## CORS 中间件 (cors.rs)

### 功能特性

- 跨域资源共享支持
- 可配置的允许源
- 预检请求处理
- 安全头设置

### 实现代码

```rust
use axum::{
    extract::Request,
    http::{header, HeaderValue, Method, StatusCode},
    middleware::Next,
    response::Response,
};
use tower_http::cors::{Any, CorsLayer};
use tracing::info;

/// CORS 配置
#[derive(Debug, Clone)]
pub struct CorsConfig {
    pub allowed_origins: Vec<String>,
    pub allowed_methods: Vec<Method>,
    pub allowed_headers: Vec<String>,
    pub max_age: u64,
    pub allow_credentials: bool,
}

impl Default for CorsConfig {
    fn default() -> Self {
        Self {
            allowed_origins: vec![
                "http://localhost:3000".to_string(),
                "http://localhost:5173".to_string(),
                "http://127.0.0.1:3000".to_string(),
                "http://127.0.0.1:5173".to_string(),
            ],
            allowed_methods: vec![
                Method::GET,
                Method::POST,
                Method::PUT,
                Method::DELETE,
                Method::PATCH,
                Method::OPTIONS,
            ],
            allowed_headers: vec![
                "content-type".to_string(),
                "authorization".to_string(),
                "x-requested-with".to_string(),
                "x-api-key".to_string(),
            ],
            max_age: 3600,
            allow_credentials: true,
        }
    }
}

/// 创建 CORS 层
pub fn create_cors_layer(config: CorsConfig) -> CorsLayer {
    let mut cors = CorsLayer::new()
        .allow_methods(config.allowed_methods)
        .allow_headers(
            config
                .allowed_headers
                .iter()
                .map(|h| h.parse().unwrap())
                .collect::<Vec<_>>(),
        )
        .max_age(std::time::Duration::from_secs(config.max_age));

    // 设置允许的源
    if config.allowed_origins.contains(&"*".to_string()) {
        cors = cors.allow_origin(Any);
    } else {
        cors = cors.allow_origin(
            config
                .allowed_origins
                .iter()
                .map(|origin| origin.parse().unwrap())
                .collect::<Vec<HeaderValue>>(),
        );
    }

    // 设置是否允许凭据
    if config.allow_credentials {
        cors = cors.allow_credentials(true);
    }

    info!(target = "udmin", "CORS middleware configured");
    cors
}

/// 自定义 CORS 中间件
pub async fn cors_middleware(
    request: Request,
    next: Next,
) -> Response {
    let origin = request
        .headers()
        .get(header::ORIGIN)
        .and_then(|v| v.to_str().ok());

    let method = request.method();
    
    // 处理预检请求
    if method == Method::OPTIONS {
        let mut response = Response::builder()
            .status(StatusCode::OK)
            .body(axum::body::Body::empty())
            .unwrap();

        let headers = response.headers_mut();
        
        if let Some(origin) = origin {
            headers.insert(
                header::ACCESS_CONTROL_ALLOW_ORIGIN,
                HeaderValue::from_str(origin).unwrap(),
            );
        }
        
        headers.insert(
            header::ACCESS_CONTROL_ALLOW_METHODS,
            HeaderValue::from_static("GET, POST, PUT, DELETE, PATCH, OPTIONS"),
        );
        
        headers.insert(
            header::ACCESS_CONTROL_ALLOW_HEADERS,
            HeaderValue::from_static("content-type, authorization, x-requested-with, x-api-key"),
        );
        
        headers.insert(
            header::ACCESS_CONTROL_MAX_AGE,
            HeaderValue::from_static("3600"),
        );
        
        headers.insert(
            header::ACCESS_CONTROL_ALLOW_CREDENTIALS,
            HeaderValue::from_static("true"),
        );

        return response;
    }

    let mut response = next.run(request).await;
    
    // 为实际请求添加 CORS 头
    let headers = response.headers_mut();
    
    if let Some(origin) = origin {
        headers.insert(
            header::ACCESS_CONTROL_ALLOW_ORIGIN,
            HeaderValue::from_str(origin).unwrap(),
        );
    }
    
    headers.insert(
        header::ACCESS_CONTROL_ALLOW_CREDENTIALS,
        HeaderValue::from_static("true"),
    );

    response
}
```

## 请求日志中间件 (logging.rs)

### 功能特性

- 请求响应日志记录
- 性能监控
- 错误追踪
- 结构化日志
- 请求ID追踪

### 实现代码

```rust
use axum::{
    extract::{MatchedPath, Request},
    http::StatusCode,
    middleware::Next,
    response::Response,
};
use std::time::Instant;
use tracing::{error, info, warn};
use uuid::Uuid;

/// 请求日志中间件
pub async fn request_logging_middleware(
    request: Request,
    next: Next,
) -> Response {
    let start_time = Instant::now();
    let request_id = Uuid::new_v4().to_string();
    
    // 提取请求信息
    let method = request.method().clone();
    let uri = request.uri().clone();
    let version = request.version();
    let user_agent = request
        .headers()
        .get("user-agent")
        .and_then(|v| v.to_str().ok())
        .unwrap_or("unknown");
    let remote_addr = request
        .headers()
        .get("x-forwarded-for")
        .and_then(|v| v.to_str().ok())
        .or_else(|| {
            request
                .headers()
                .get("x-real-ip")
                .and_then(|v| v.to_str().ok())
        })
        .unwrap_or("unknown");
    
    // 获取匹配的路径模式
    let matched_path = request
        .extensions()
        .get::<MatchedPath>()
        .map(|mp| mp.as_str())
        .unwrap_or(uri.path());

    info!(
        target = "udmin",
        request_id = %request_id,
        method = %method,
        uri = %uri,
        path = %matched_path,
        version = ?version,
        user_agent = %user_agent,
        remote_addr = %remote_addr,
        "Request started"
    );

    // 执行请求
    let response = next.run(request).await;
    
    // 计算请求耗时
    let duration = start_time.elapsed();
    let status = response.status();
    
    // 根据状态码选择日志级别
    match status.as_u16() {
        200..=299 => {
            info!(
                target = "udmin",
                request_id = %request_id,
                method = %method,
                uri = %uri,
                path = %matched_path,
                status = %status.as_u16(),
                duration_ms = %duration.as_millis(),
                "Request completed successfully"
            );
        }
        300..=399 => {
            info!(
                target = "udmin",
                request_id = %request_id,
                method = %method,
                uri = %uri,
                path = %matched_path,
                status = %status.as_u16(),
                duration_ms = %duration.as_millis(),
                "Request redirected"
            );
        }
        400..=499 => {
            warn!(
                target = "udmin",
                request_id = %request_id,
                method = %method,
                uri = %uri,
                path = %matched_path,
                status = %status.as_u16(),
                duration_ms = %duration.as_millis(),
                "Client error"
            );
        }
        500..=599 => {
            error!(
                target = "udmin",
                request_id = %request_id,
                method = %method,
                uri = %uri,
                path = %matched_path,
                status = %status.as_u16(),
                duration_ms = %duration.as_millis(),
                "Server error"
            );
        }
        _ => {
            info!(
                target = "udmin",
                request_id = %request_id,
                method = %method,
                uri = %uri,
                path = %matched_path,
                status = %status.as_u16(),
                duration_ms = %duration.as_millis(),
                "Request completed"
            );
        }
    }

    response
}

/// 性能监控中间件
pub async fn performance_monitoring_middleware(
    request: Request,
    next: Next,
) -> Response {
    let start_time = Instant::now();
    let method = request.method().clone();
    let uri = request.uri().clone();
    
    let response = next.run(request).await;
    let duration = start_time.elapsed();
    
    // 记录慢请求
    if duration.as_millis() > 1000 {
        warn!(
            target = "udmin",
            method = %method,
            uri = %uri,
            duration_ms = %duration.as_millis(),
            "Slow request detected"
        );
    }
    
    // 记录性能指标
    info!(
        target = "udmin.performance",
        method = %method,
        uri = %uri,
        status = %response.status().as_u16(),
        duration_ms = %duration.as_millis(),
        "Performance metrics"
    );
    
    response
}
```

## HTTP 客户端中间件 (http_client.rs)

### 功能特性

- HTTP 客户端封装
- 请求重试机制
- 超时控制
- 请求日志
- 错误处理

### 实现代码

```rust
use reqwest::{Client, ClientBuilder, Response};
use serde::{Deserialize, Serialize};
use std::time::Duration;
use tracing::{error, info, warn};
use url::Url;

use crate::error::AppError;

/// HTTP 客户端配置
#[derive(Debug, Clone)]
pub struct HttpClientConfig {
    pub timeout: Duration,
    pub connect_timeout: Duration,
    pub max_retries: u32,
    pub retry_delay: Duration,
    pub user_agent: String,
}

impl Default for HttpClientConfig {
    fn default() -> Self {
        Self {
            timeout: Duration::from_secs(30),
            connect_timeout: Duration::from_secs(10),
            max_retries: 3,
            retry_delay: Duration::from_millis(1000),
            user_agent: "UdminAI/1.0".to_string(),
        }
    }
}

/// HTTP 客户端包装器
#[derive(Debug, Clone)]
pub struct HttpClient {
    client: Client,
    config: HttpClientConfig,
}

impl HttpClient {
    /// 创建新的 HTTP 客户端
    pub fn new(config: HttpClientConfig) -> Result<Self, AppError> {
        let client = ClientBuilder::new()
            .timeout(config.timeout)
            .connect_timeout(config.connect_timeout)
            .user_agent(&config.user_agent)
            .build()
            .map_err(|e| AppError::InternalServerError(format!("创建HTTP客户端失败: {}", e)))?;

        Ok(Self { client, config })
    }

    /// 发送 GET 请求
    pub async fn get(&self, url: &str) -> Result<Response, AppError> {
        self.request_with_retry("GET", url, None::<()>).await
    }

    /// 发送 POST 请求
    pub async fn post<T: Serialize>(&self, url: &str, body: &T) -> Result<Response, AppError> {
        self.request_with_retry("POST", url, Some(body)).await
    }

    /// 发送 PUT 请求
    pub async fn put<T: Serialize>(&self, url: &str, body: &T) -> Result<Response, AppError> {
        self.request_with_retry("PUT", url, Some(body)).await
    }

    /// 发送 DELETE 请求
    pub async fn delete(&self, url: &str) -> Result<Response, AppError> {
        self.request_with_retry("DELETE", url, None::<()>).await
    }

    /// 带重试的请求
    async fn request_with_retry<T: Serialize>(
        &self,
        method: &str,
        url: &str,
        body: Option<&T>,
    ) -> Result<Response, AppError> {
        let parsed_url = Url::parse(url)
            .map_err(|e| AppError::BadRequest(format!("无效的URL: {}", e)))?;

        let mut last_error = None;

        for attempt in 0..=self.config.max_retries {
            let start_time = std::time::Instant::now();

            info!(
                target = "udmin",
                method = %method,
                url = %url,
                attempt = %attempt,
                "HTTP request started"
            );

            let result = self.make_request(method, &parsed_url, body).await;
            let duration = start_time.elapsed();

            match result {
                Ok(response) => {
                    let status = response.status();
                    
                    info!(
                        target = "udmin",
                        method = %method,
                        url = %url,
                        status = %status.as_u16(),
                        duration_ms = %duration.as_millis(),
                        attempt = %attempt,
                        "HTTP request completed"
                    );

                    // 如果是服务器错误且还有重试次数，则重试
                    if status.is_server_error() && attempt < self.config.max_retries {
                        warn!(
                            target = "udmin",
                            method = %method,
                            url = %url,
                            status = %status.as_u16(),
                            attempt = %attempt,
                            "Server error, retrying"
                        );
                        
                        tokio::time::sleep(self.config.retry_delay).await;
                        continue;
                    }

                    return Ok(response);
                }
                Err(e) => {
                    error!(
                        target = "udmin",
                        method = %method,
                        url = %url,
                        error = %e,
                        duration_ms = %duration.as_millis(),
                        attempt = %attempt,
                        "HTTP request failed"
                    );

                    last_error = Some(e);

                    // 如果还有重试次数，则等待后重试
                    if attempt < self.config.max_retries {
                        tokio::time::sleep(self.config.retry_delay).await;
                    }
                }
            }
        }

        Err(last_error.unwrap_or_else(|| {
            AppError::InternalServerError("HTTP请求失败".to_string())
        }))
    }

    /// 执行实际的 HTTP 请求
    async fn make_request<T: Serialize>(
        &self,
        method: &str,
        url: &Url,
        body: Option<&T>,
    ) -> Result<Response, AppError> {
        let mut request_builder = match method {
            "GET" => self.client.get(url.clone()),
            "POST" => self.client.post(url.clone()),
            "PUT" => self.client.put(url.clone()),
            "DELETE" => self.client.delete(url.clone()),
            _ => {
                return Err(AppError::BadRequest(format!(
                    "不支持的HTTP方法: {}",
                    method
                )))
            }
        };

        // 添加请求体
        if let Some(body) = body {
            request_builder = request_builder.json(body);
        }

        // 发送请求
        let response = request_builder
            .send()
            .await
            .map_err(|e| AppError::InternalServerError(format!("HTTP请求失败: {}", e)))?;

        Ok(response)
    }

    /// 发送 JSON 请求并解析响应
    pub async fn json_request<T, R>(
        &self,
        method: &str,
        url: &str,
        body: Option<&T>,
    ) -> Result<R, AppError>
    where
        T: Serialize,
        R: for<'de> Deserialize<'de>,
    {
        let response = match method {
            "GET" => self.get(url).await?,
            "POST" => {
                if let Some(body) = body {
                    self.post(url, body).await?
                } else {
                    return Err(AppError::BadRequest("POST请求需要请求体".to_string()));
                }
            }
            "PUT" => {
                if let Some(body) = body {
                    self.put(url, body).await?
                } else {
                    return Err(AppError::BadRequest("PUT请求需要请求体".to_string()));
                }
            }
            "DELETE" => self.delete(url).await?,
            _ => {
                return Err(AppError::BadRequest(format!(
                    "不支持的HTTP方法: {}",
                    method
                )))
            }
        };

        // 检查响应状态
        if !response.status().is_success() {
            let status = response.status();
            let error_text = response
                .text()
                .await
                .unwrap_or_else(|_| "无法读取错误响应".to_string());
            
            return Err(AppError::InternalServerError(format!(
                "HTTP请求失败: {} - {}",
                status, error_text
            )));
        }

        // 解析 JSON 响应
        let json_response = response
            .json::<R>()
            .await
            .map_err(|e| AppError::InternalServerError(format!("解析JSON响应失败: {}", e)))?;

        Ok(json_response)
    }
}
```

## 限流中间件 (rate_limit.rs)

### 功能特性

- 基于令牌桶的限流
- 支持不同的限流策略
- IP 级别限流
- 用户级别限流
- 动态配置

### 实现代码

```rust
use axum::{
    extract::{Request, State},
    http::StatusCode,
    middleware::Next,
    response::Response,
};
use std::{
    collections::HashMap,
    sync::{Arc, Mutex},
    time::{Duration, Instant},
};
use tracing::{info, warn};

use crate::{error::AppError, middlewares::auth::AuthContext};

/// 令牌桶
#[derive(Debug, Clone)]
struct TokenBucket {
    capacity: u32,
    tokens: u32,
    last_refill: Instant,
    refill_rate: u32, // tokens per second
}

impl TokenBucket {
    fn new(capacity: u32, refill_rate: u32) -> Self {
        Self {
            capacity,
            tokens: capacity,
            last_refill: Instant::now(),
            refill_rate,
        }
    }

    fn try_consume(&mut self, tokens: u32) -> bool {
        self.refill();
        
        if self.tokens >= tokens {
            self.tokens -= tokens;
            true
        } else {
            false
        }
    }

    fn refill(&mut self) {
        let now = Instant::now();
        let elapsed = now.duration_since(self.last_refill);
        let tokens_to_add = (elapsed.as_secs_f64() * self.refill_rate as f64) as u32;
        
        if tokens_to_add > 0 {
            self.tokens = (self.tokens + tokens_to_add).min(self.capacity);
            self.last_refill = now;
        }
    }
}

/// 限流器
#[derive(Debug)]
pub struct RateLimiter {
    buckets: Arc<Mutex<HashMap<String, TokenBucket>>>,
    default_capacity: u32,
    default_refill_rate: u32,
}

impl RateLimiter {
    pub fn new(default_capacity: u32, default_refill_rate: u32) -> Self {
        Self {
            buckets: Arc::new(Mutex::new(HashMap::new())),
            default_capacity,
            default_refill_rate,
        }
    }

    pub fn check_rate_limit(&self, key: &str, tokens: u32) -> bool {
        let mut buckets = self.buckets.lock().unwrap();
        
        let bucket = buckets
            .entry(key.to_string())
            .or_insert_with(|| TokenBucket::new(self.default_capacity, self.default_refill_rate));
        
        bucket.try_consume(tokens)
    }

    /// 清理过期的桶
    pub fn cleanup_expired_buckets(&self, max_idle_duration: Duration) {
        let mut buckets = self.buckets.lock().unwrap();
        let now = Instant::now();
        
        buckets.retain(|_, bucket| {
            now.duration_since(bucket.last_refill) < max_idle_duration
        });
    }
}

/// 限流配置
#[derive(Debug, Clone)]
pub struct RateLimitConfig {
    pub requests_per_second: u32,
    pub burst_capacity: u32,
    pub enable_ip_limit: bool,
    pub enable_user_limit: bool,
}

impl Default for RateLimitConfig {
    fn default() -> Self {
        Self {
            requests_per_second: 100,
            burst_capacity: 200,
            enable_ip_limit: true,
            enable_user_limit: true,
        }
    }
}

/// IP 限流中间件
pub async fn ip_rate_limit_middleware(
    State(rate_limiter): State<Arc<RateLimiter>>,
    request: Request,
    next: Next,
) -> Result<Response, AppError> {
    // 获取客户端 IP
    let client_ip = request
        .headers()
        .get("x-forwarded-for")
        .and_then(|v| v.to_str().ok())
        .and_then(|v| v.split(',').next())
        .or_else(|| {
            request
                .headers()
                .get("x-real-ip")
                .and_then(|v| v.to_str().ok())
        })
        .unwrap_or("unknown")
        .trim();

    let rate_limit_key = format!("ip:{}", client_ip);
    
    // 检查限流
    if !rate_limiter.check_rate_limit(&rate_limit_key, 1) {
        warn!(
            target = "udmin",
            client_ip = %client_ip,
            "IP rate limit exceeded"
        );
        
        return Err(AppError::TooManyRequests(
            "请求过于频繁，请稍后再试".to_string(),
        ));
    }

    info!(
        target = "udmin",
        client_ip = %client_ip,
        "IP rate limit check passed"
    );

    Ok(next.run(request).await)
}

/// 用户限流中间件
pub async fn user_rate_limit_middleware(
    State(rate_limiter): State<Arc<RateLimiter>>,
    request: Request,
    next: Next,
) -> Result<Response, AppError> {
    // 获取用户认证信息
    if let Some(auth_context) = request.extensions().get::<AuthContext>() {
        let rate_limit_key = format!("user:{}", auth_context.user_id);
        
        // 检查用户级别限流
        if !rate_limiter.check_rate_limit(&rate_limit_key, 1) {
            warn!(
                target = "udmin",
                user_id = %auth_context.user_id,
                "User rate limit exceeded"
            );
            
            return Err(AppError::TooManyRequests(
                "用户请求过于频繁，请稍后再试".to_string(),
            ));
        }

        info!(
            target = "udmin",
            user_id = %auth_context.user_id,
            "User rate limit check passed"
        );
    }

    Ok(next.run(request).await)
}

/// 创建限流中间件
pub fn create_rate_limit_middleware(
    config: RateLimitConfig,
) -> Arc<RateLimiter> {
    let rate_limiter = Arc::new(RateLimiter::new(
        config.burst_capacity,
        config.requests_per_second,
    ));

    // 启动清理任务
    let cleanup_limiter = rate_limiter.clone();
    tokio::spawn(async move {
        let mut interval = tokio::time::interval(Duration::from_secs(300)); // 5分钟清理一次
        
        loop {
            interval.tick().await;
            cleanup_limiter.cleanup_expired_buckets(Duration::from_secs(3600)); // 清理1小时未使用的桶
        }
    });

    info!(target = "udmin", "Rate limiter initialized");
    rate_limiter
}
```

## WebSocket 中间件 (ws.rs)

### 功能特性

- WebSocket 连接管理
- 实时消息推送
- 连接认证
- 心跳检测
- 广播支持

### 实现代码

```rust
use axum::{
    extract::{ws::WebSocket, Query, State, WebSocketUpgrade},
    response::Response,
};
use futures_util::{sink::SinkExt, stream::StreamExt};
use serde::{Deserialize, Serialize};
use std::{
    collections::HashMap,
    sync::{Arc, RwLock},
    time::{Duration, Instant},
};
use tokio::sync::mpsc;
use tracing::{error, info, warn};
use uuid::Uuid;

use crate::{
    error::AppError,
    services::user_service,
    AppState,
};

/// WebSocket 连接信息
#[derive(Debug, Clone)]
pub struct ConnectionInfo {
    pub id: String,
    pub user_id: Option<String>,
    pub connected_at: Instant,
    pub last_ping: Instant,
    pub sender: mpsc::UnboundedSender<WebSocketMessage>,
}

/// WebSocket 消息类型
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type", content = "data")]
pub enum WebSocketMessage {
    /// 认证消息
    Auth { token: String },
    /// 认证成功
    AuthSuccess { user_id: String },
    /// 认证失败
    AuthError { message: String },
    /// 心跳包
    Ping,
    /// 心跳响应
    Pong,
    /// 流程执行状态更新
    FlowExecutionUpdate {
        execution_id: String,
        status: String,
        progress: Option<f64>,
        message: Option<String>,
    },
    /// 任务执行状态更新
    JobExecutionUpdate {
        job_id: String,
        execution_id: String,
        status: String,
        message: Option<String>,
    },
    /// 系统通知
    SystemNotification {
        title: String,
        message: String,
        level: String,
    },
    /// 用户通知
    UserNotification {
        id: String,
        title: String,
        message: String,
        created_at: String,
    },
    /// 错误消息
    Error { message: String },
}

/// WebSocket 连接管理器
#[derive(Debug)]
pub struct WebSocketManager {
    connections: Arc<RwLock<HashMap<String, ConnectionInfo>>>,
    user_connections: Arc<RwLock<HashMap<String, Vec<String>>>>, // user_id -> connection_ids
}

impl WebSocketManager {
    pub fn new() -> Self {
        Self {
            connections: Arc::new(RwLock::new(HashMap::new())),
            user_connections: Arc::new(RwLock::new(HashMap::new())),
        }
    }

    /// 添加连接
    pub fn add_connection(&self, connection_info: ConnectionInfo) {
        let connection_id = connection_info.id.clone();
        let user_id = connection_info.user_id.clone();
        
        // 添加到连接列表
        self.connections.write().unwrap().insert(connection_id.clone(), connection_info);
        
        // 如果有用户ID，添加到用户连接映射
        if let Some(user_id) = user_id {
            self.user_connections
                .write()
                .unwrap()
                .entry(user_id)
                .or_insert_with(Vec::new)
                .push(connection_id.clone());
        }
        
        info!(
            target = "udmin",
            connection_id = %connection_id,
            "WebSocket connection added"
        );
    }

    /// 移除连接
    pub fn remove_connection(&self, connection_id: &str) {
        let mut connections = self.connections.write().unwrap();
        
        if let Some(connection_info) = connections.remove(connection_id) {
            // 从用户连接映射中移除
            if let Some(user_id) = &connection_info.user_id {
                let mut user_connections = self.user_connections.write().unwrap();
                if let Some(user_conn_list) = user_connections.get_mut(user_id) {
                    user_conn_list.retain(|id| id != connection_id);
                    if user_conn_list.is_empty() {
                        user_connections.remove(user_id);
                    }
                }
            }
            
            info!(
                target = "udmin",
                connection_id = %connection_id,
                user_id = ?connection_info.user_id,
                "WebSocket connection removed"
            );
        }
    }

    /// 向指定连接发送消息
    pub fn send_to_connection(&self, connection_id: &str, message: WebSocketMessage) -> bool {
        let connections = self.connections.read().unwrap();
        
        if let Some(connection_info) = connections.get(connection_id) {
            match connection_info.sender.send(message) {
                Ok(_) => true,
                Err(e) => {
                    warn!(
                        target = "udmin",
                        connection_id = %connection_id,
                        error = %e,
                        "Failed to send message to connection"
                    );
                    false
                }
            }
        } else {
            false
        }
    }

    /// 向指定用户的所有连接发送消息
    pub fn send_to_user(&self, user_id: &str, message: WebSocketMessage) -> usize {
        let user_connections = self.user_connections.read().unwrap();
        let mut sent_count = 0;
        
        if let Some(connection_ids) = user_connections.get(user_id) {
            for connection_id in connection_ids {
                if self.send_to_connection(connection_id, message.clone()) {
                    sent_count += 1;
                }
            }
        }
        
        info!(
            target = "udmin",
            user_id = %user_id,
            sent_count = %sent_count,
            "Message sent to user connections"
        );
        
        sent_count
    }

    /// 广播消息给所有连接
    pub fn broadcast(&self, message: WebSocketMessage) -> usize {
        let connections = self.connections.read().unwrap();
        let mut sent_count = 0;
        
        for (connection_id, connection_info) in connections.iter() {
            match connection_info.sender.send(message.clone()) {
                Ok(_) => sent_count += 1,
                Err(e) => {
                    warn!(
                        target = "udmin",
                        connection_id = %connection_id,
                        error = %e,
                        "Failed to broadcast message"
                    );
                }
            }
        }
        
        info!(
            target = "udmin",
            sent_count = %sent_count,
            total_connections = %connections.len(),
            "Message broadcasted"
        );
        
        sent_count
    }

    /// 获取连接统计信息
    pub fn get_stats(&self) -> WebSocketStats {
        let connections = self.connections.read().unwrap();
        let user_connections = self.user_connections.read().unwrap();
        
        WebSocketStats {
            total_connections: connections.len(),
            authenticated_connections: connections.values().filter(|c| c.user_id.is_some()).count(),
            unique_users: user_connections.len(),
        }
    }

    /// 清理过期连接
    pub fn cleanup_stale_connections(&self, timeout: Duration) {
        let now = Instant::now();
        let connections = self.connections.read().unwrap();
        let stale_connections: Vec<String> = connections
            .iter()
            .filter(|(_, info)| now.duration_since(info.last_ping) > timeout)
            .map(|(id, _)| id.clone())
            .collect();
        
        drop(connections);
        
        for connection_id in stale_connections {
            self.remove_connection(&connection_id);
            warn!(
                target = "udmin",
                connection_id = %connection_id,
                "Removed stale WebSocket connection"
            );
        }
    }
}

/// WebSocket 统计信息
#[derive(Debug, Serialize)]
pub struct WebSocketStats {
    pub total_connections: usize,
    pub authenticated_connections: usize,
    pub unique_users: usize,
}

/// WebSocket 查询参数
#[derive(Debug, Deserialize)]
pub struct WebSocketQuery {
    pub token: Option<String>,
}

/// WebSocket 升级处理器
pub async fn websocket_handler(
    ws: WebSocketUpgrade,
    Query(params): Query<WebSocketQuery>,
    State(state): State<AppState>,
) -> Response {
    ws.on_upgrade(move |socket| handle_websocket(socket, params.token, state))
}

/// 处理 WebSocket 连接
async fn handle_websocket(
    socket: WebSocket,
    token: Option<String>,
    state: AppState,
) {
    let connection_id = Uuid::new_v4().to_string();
    let (mut sender, mut receiver) = socket.split();
    let (tx, mut rx) = mpsc::unbounded_channel::<WebSocketMessage>();
    
    info!(
        target = "udmin",
        connection_id = %connection_id,
        "WebSocket connection established"
    );

    // 创建连接信息
    let connection_info = ConnectionInfo {
        id: connection_id.clone(),
        user_id: None,
        connected_at: Instant::now(),
        last_ping: Instant::now(),
        sender: tx,
    };
    
    // 添加到连接管理器
    state.ws_manager.add_connection(connection_info);
    
    // 如果提供了token，尝试认证
    let mut authenticated_user_id = None;
    if let Some(token) = token {
        match authenticate_websocket_token(&token, &state).await {
            Ok(user_id) => {
                authenticated_user_id = Some(user_id.clone());
                
                // 更新连接信息
                if let Some(mut connection_info) = state.connections.write().unwrap().get_mut(&connection_id) {
                    connection_info.user_id = Some(user_id.clone());
                }
                
                // 发送认证成功消息
                let _ = sender.send(axum::extract::ws::Message::Text(
                    serde_json::to_string(&WebSocketMessage::AuthSuccess { user_id }).unwrap()
                )).await;
                
                info!(
                    target = "udmin",
                    connection_id = %connection_id,
                    user_id = %authenticated_user_id.as_ref().unwrap(),
                    "WebSocket connection authenticated"
                );
            }
            Err(e) => {
                warn!(
                    target = "udmin",
                    connection_id = %connection_id,
                    error = %e,
                    "WebSocket authentication failed"
                );
                
                let _ = sender.send(axum::extract::ws::Message::Text(
                    serde_json::to_string(&WebSocketMessage::AuthError {
                        message: "认证失败".to_string()
                    }).unwrap()
                )).await;
            }
        }
    }
    
    // 启动消息发送任务
    let connection_id_clone = connection_id.clone();
    let ws_manager_clone = state.ws_manager.clone();
    let send_task = tokio::spawn(async move {
        while let Some(message) = rx.recv().await {
            let text = match serde_json::to_string(&message) {
                Ok(text) => text,
                Err(e) => {
                    error!(
                        target = "udmin",
                        connection_id = %connection_id_clone,
                        error = %e,
                        "Failed to serialize WebSocket message"
                    );
                    continue;
                }
            };
            
            if sender.send(axum::extract::ws::Message::Text(text)).await.is_err() {
                break;
            }
        }
        
        // 移除连接
        ws_manager_clone.remove_connection(&connection_id_clone);
    });
    
    // 启动心跳任务
    let connection_id_clone = connection_id.clone();
    let ws_manager_clone = state.ws_manager.clone();
    let heartbeat_task = tokio::spawn(async move {
        let mut interval = tokio::time::interval(Duration::from_secs(30));
        
        loop {
            interval.tick().await;
            
            if !ws_manager_clone.send_to_connection(
                &connection_id_clone,
                WebSocketMessage::Ping,
            ) {
                break;
            }
        }
    });
    
    // 处理接收到的消息
    while let Some(msg) = receiver.next().await {
        match msg {
            Ok(axum::extract::ws::Message::Text(text)) => {
                match serde_json::from_str::<WebSocketMessage>(&text) {
                    Ok(WebSocketMessage::Auth { token }) => {
                        // 处理认证消息
                        match authenticate_websocket_token(&token, &state).await {
                            Ok(user_id) => {
                                authenticated_user_id = Some(user_id.clone());
                                
                                let _ = state.ws_manager.send_to_connection(
                                    &connection_id,
                                    WebSocketMessage::AuthSuccess { user_id },
                                );
                            }
                            Err(_) => {
                                let _ = state.ws_manager.send_to_connection(
                                    &connection_id,
                                    WebSocketMessage::AuthError {
                                        message: "认证失败".to_string(),
                                    },
                                );
                            }
                        }
                    }
                    Ok(WebSocketMessage::Pong) => {
                        // 更新最后ping时间
                        // 这里可以更新连接的last_ping时间
                    }
                    Ok(_) => {
                        // 处理其他消息类型
                    }
                    Err(e) => {
                        warn!(
                            target = "udmin",
                            connection_id = %connection_id,
                            error = %e,
                            "Failed to parse WebSocket message"
                        );
                    }
                }
            }
            Ok(axum::extract::ws::Message::Close(_)) => {
                info!(
                    target = "udmin",
                    connection_id = %connection_id,
                    "WebSocket connection closed by client"
                );
                break;
            }
            Err(e) => {
                error!(
                    target = "udmin",
                    connection_id = %connection_id,
                    error = %e,
                    "WebSocket error"
                );
                break;
            }
            _ => {}
        }
    }
    
    // 清理任务
    send_task.abort();
    heartbeat_task.abort();
    state.ws_manager.remove_connection(&connection_id);
    
    info!(
        target = "udmin",
        connection_id = %connection_id,
        "WebSocket connection closed"
    );
}

/// 认证 WebSocket Token
async fn authenticate_websocket_token(
    token: &str,
    state: &AppState,
) -> Result<String, AppError> {
    use jsonwebtoken::{decode, DecodingKey, Validation};
    use crate::middlewares::auth::Claims;
    
    // 验证 JWT Token
    let claims = decode::<Claims>(
        token,
        &DecodingKey::from_secret(state.config.jwt_secret.as_ref()),
        &Validation::default(),
    )
    .map_err(|_| AppError::Unauthorized("无效的认证令牌".to_string()))?
    .claims;
    
    // 检查用户是否存在且活跃
    let user = user_service::find_by_id(&state.db, &claims.sub)
        .await
        .map_err(|_| AppError::Unauthorized("用户不存在".to_string()))?;
    
    if user.status != crate::models::user::UserStatus::Active {
        return Err(AppError::Unauthorized("用户账户已被禁用".to_string()));
    }
    
    Ok(claims.sub)
}

/// 启动 WebSocket 管理器清理任务
pub fn start_websocket_cleanup_task(ws_manager: Arc<WebSocketManager>) {
    tokio::spawn(async move {
        let mut interval = tokio::time::interval(Duration::from_secs(60));
        
        loop {
            interval.tick().await;
            ws_manager.cleanup_stale_connections(Duration::from_secs(300)); // 5分钟超时
        }
    });
}
```

## SSE 中间件 (sse.rs)

### 功能特性

- Server-Sent Events 支持
- 实时事件推送
- 连接管理
- 事件过滤
- 重连支持

### 实现代码

```rust
use axum::{
    extract::{Query, State},
    http::{header, HeaderValue, StatusCode},
    response::{sse::Event, Response, Sse},
};
use futures_util::stream::{self, Stream};
use serde::{Deserialize, Serialize};
use std::{
    collections::HashMap,
    convert::Infallible,
    sync::{Arc, RwLock},
    time::{Duration, SystemTime, UNIX_EPOCH},
};
use tokio::sync::mpsc;
use tokio_stream::wrappers::UnboundedReceiverStream;
use tracing::{error, info, warn};
use uuid::Uuid;

use crate::{
    error::AppError,
    middlewares::auth::AuthContext,
    AppState,
};

/// SSE 事件类型
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type", content = "data")]
pub enum SseEvent {
    /// 流程执行状态更新
    FlowExecutionUpdate {
        execution_id: String,
        flow_id: String,
        status: String,
        progress: Option<f64>,
        message: Option<String>,
        timestamp: u64,
    },
    /// 任务执行状态更新
    JobExecutionUpdate {
        job_id: String,
        execution_id: String,
        status: String,
        message: Option<String>,
        timestamp: u64,
    },
    /// 系统通知
    SystemNotification {
        id: String,
        title: String,
        message: String,
        level: String,
        timestamp: u64,
    },
    /// 用户通知
    UserNotification {
        id: String,
        title: String,
        message: String,
        timestamp: u64,
    },
    /// 系统状态更新
    SystemStatus {
        cpu_usage: f64,
        memory_usage: f64,
        disk_usage: f64,
        active_connections: usize,
        timestamp: u64,
    },
    /// 心跳事件
    Heartbeat {
        timestamp: u64,
    },
}

/// SSE 连接信息
#[derive(Debug)]
struct SseConnection {
    id: String,
    user_id: Option<String>,
    sender: mpsc::UnboundedSender<Result<Event, Infallible>>,
    filters: Vec<String>,
    created_at: SystemTime,
}

/// SSE 连接管理器
#[derive(Debug)]
pub struct SseManager {
    connections: Arc<RwLock<HashMap<String, SseConnection>>>,
    user_connections: Arc<RwLock<HashMap<String, Vec<String>>>>,
}

impl SseManager {
    pub fn new() -> Self {
        Self {
            connections: Arc::new(RwLock::new(HashMap::new())),
            user_connections: Arc<RwLock::new(HashMap::new())),
        }
    }

    /// 添加 SSE 连接
    pub fn add_connection(
        &self,
        connection_id: String,
        user_id: Option<String>,
        sender: mpsc::UnboundedSender<Result<Event, Infallible>>,
        filters: Vec<String>,
    ) {
        let connection = SseConnection {
            id: connection_id.clone(),
            user_id: user_id.clone(),
            sender,
            filters,
            created_at: SystemTime::now(),
        };
        
        // 添加到连接列表
        self.connections.write().unwrap().insert(connection_id.clone(), connection);
        
        // 如果有用户ID，添加到用户连接映射
        if let Some(user_id) = user_id {
            self.user_connections
                .write()
                .unwrap()
                .entry(user_id)
                .or_insert_with(Vec::new)
                .push(connection_id.clone());
        }
        
        info!(
            target = "udmin",
            connection_id = %connection_id,
            "SSE connection added"
        );
    }

    /// 移除 SSE 连接
    pub fn remove_connection(&self, connection_id: &str) {
        let mut connections = self.connections.write().unwrap();
        
        if let Some(connection) = connections.remove(connection_id) {
            // 从用户连接映射中移除
            if let Some(user_id) = &connection.user_id {
                let mut user_connections = self.user_connections.write().unwrap();
                if let Some(user_conn_list) = user_connections.get_mut(user_id) {
                    user_conn_list.retain(|id| id != connection_id);
                    if user_conn_list.is_empty() {
                        user_connections.remove(user_id);
                    }
                }
            }
            
            info!(
                target = "udmin",
                connection_id = %connection_id,
                user_id = ?connection.user_id,
                "SSE connection removed"
            );
        }
    }

    /// 发送事件到指定连接
    pub fn send_to_connection(&self, connection_id: &str, event: SseEvent) -> bool {
        let connections = self.connections.read().unwrap();
        
        if let Some(connection) = connections.get(connection_id) {
            // 检查事件过滤器
            if !connection.filters.is_empty() {
                let event_type = match &event {
                    SseEvent::FlowExecutionUpdate { .. } => "flow_execution",
                    SseEvent::JobExecutionUpdate { .. } => "job_execution",
                    SseEvent::SystemNotification { .. } => "system_notification",
                    SseEvent::UserNotification { .. } => "user_notification",
                    SseEvent::SystemStatus { .. } => "system_status",
                    SseEvent::Heartbeat { .. } => "heartbeat",
                };
                
                if !connection.filters.contains(&event_type.to_string()) {
                    return true; // 过滤掉，但不算失败
                }
            }
            
            let sse_event = match create_sse_event(&event) {
                Ok(event) => event,
                Err(e) => {
                    error!(
                        target = "udmin",
                        connection_id = %connection_id,
                        error = %e,
                        "Failed to create SSE event"
                    );
                    return false;
                }
            };
            
            match connection.sender.send(Ok(sse_event)) {
                Ok(_) => true,
                Err(e) => {
                    warn!(
                        target = "udmin",
                        connection_id = %connection_id,
                        error = %e,
                        "Failed to send SSE event"
                    );
                    false
                }
            }
        } else {
            false
        }
    }

    /// 发送事件到指定用户的所有连接
    pub fn send_to_user(&self, user_id: &str, event: SseEvent) -> usize {
        let user_connections = self.user_connections.read().unwrap();
        let mut sent_count = 0;
        
        if let Some(connection_ids) = user_connections.get(user_id) {
            for connection_id in connection_ids {
                if self.send_to_connection(connection_id, event.clone()) {
                    sent_count += 1;
                }
            }
        }
        
        info!(
            target = "udmin",
            user_id = %user_id,
            sent_count = %sent_count,
            "SSE event sent to user connections"
        );
        
        sent_count
    }

    /// 广播事件到所有连接
    pub fn broadcast(&self, event: SseEvent) -> usize {
        let connections = self.connections.read().unwrap();
        let mut sent_count = 0;
        
        for (connection_id, _) in connections.iter() {
            if self.send_to_connection(connection_id, event.clone()) {
                sent_count += 1;
            }
        }
        
        info!(
            target = "udmin",
            sent_count = %sent_count,
            total_connections = %connections.len(),
            "SSE event broadcasted"
        );
        
        sent_count
    }

    /// 获取连接统计信息
    pub fn get_stats(&self) -> SseStats {
        let connections = self.connections.read().unwrap();
        let user_connections = self.user_connections.read().unwrap();
        
        SseStats {
            total_connections: connections.len(),
            authenticated_connections: connections.values().filter(|c| c.user_id.is_some()).count(),
            unique_users: user_connections.len(),
        }
    }
}

/// SSE 统计信息
#[derive(Debug, Serialize)]
pub struct SseStats {
    pub total_connections: usize,
    pub authenticated_connections: usize,
    pub unique_users: usize,
}

/// SSE 查询参数
#[derive(Debug, Deserialize)]
pub struct SseQuery {
    pub filters: Option<String>, // 逗号分隔的事件类型过滤器
    pub last_event_id: Option<String>,
}

/// SSE 处理器
pub async fn sse_handler(
    Query(params): Query<SseQuery>,
    State(state): State<AppState>,
    auth_context: Option<AuthContext>,
) -> Result<Response, AppError> {
    let connection_id = Uuid::new_v4().to_string();
    let (tx, rx) = mpsc::unbounded_channel();
    
    // 解析过滤器
    let filters = params
        .filters
        .map(|f| f.split(',').map(|s| s.trim().to_string()).collect())
        .unwrap_or_default();
    
    // 添加连接到管理器
    state.sse_manager.add_connection(
        connection_id.clone(),
        auth_context.as_ref().map(|ctx| ctx.user_id.clone()),
        tx,
        filters,
    );
    
    info!(
        target = "udmin",
        connection_id = %connection_id,
        user_id = ?auth_context.as_ref().map(|ctx| &ctx.user_id),
        "SSE connection established"
    );
    
    // 发送初始心跳
    let initial_heartbeat = SseEvent::Heartbeat {
        timestamp: SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .unwrap()
            .as_secs(),
    };
    
    state.sse_manager.send_to_connection(&connection_id, initial_heartbeat);
    
    // 创建事件流
    let stream = UnboundedReceiverStream::new(rx);
    
    // 启动心跳任务
    let connection_id_clone = connection_id.clone();
    let sse_manager_clone = state.sse_manager.clone();
    tokio::spawn(async move {
        let mut interval = tokio::time::interval(Duration::from_secs(30));
        
        loop {
            interval.tick().await;
            
            let heartbeat = SseEvent::Heartbeat {
                timestamp: SystemTime::now()
                    .duration_since(UNIX_EPOCH)
                    .unwrap()
                    .as_secs(),
            };
            
            if !sse_manager_clone.send_to_connection(&connection_id_clone, heartbeat) {
                break;
            }
        }
        
        // 清理连接
        sse_manager_clone.remove_connection(&connection_id_clone);
    });
    
    let sse = Sse::new(stream).keep_alive(
        axum::response::sse::KeepAlive::new()
            .interval(Duration::from_secs(15))
            .text("keep-alive-text"),
    );
    
    Ok(sse.into_response())
}

/// 创建 SSE 事件
fn create_sse_event(event: &SseEvent) -> Result<Event, serde_json::Error> {
    let event_type = match event {
        SseEvent::FlowExecutionUpdate { .. } => "flow_execution_update",
        SseEvent::JobExecutionUpdate { .. } => "job_execution_update",
        SseEvent::SystemNotification { .. } => "system_notification",
        SseEvent::UserNotification { .. } => "user_notification",
        SseEvent::SystemStatus { .. } => "system_status",
        SseEvent::Heartbeat { .. } => "heartbeat",
    };
    
    let data = serde_json::to_string(event)?;
    
    Ok(Event::default()
        .event(event_type)
        .data(data))
}

/// 启动 SSE 管理器清理任务
pub fn start_sse_cleanup_task(sse_manager: Arc<SseManager>) {
    tokio::spawn(async move {
        let mut interval = tokio::time::interval(Duration::from_secs(300)); // 5分钟清理一次
        
        loop {
            interval.tick().await;
            
            // 这里可以添加清理逻辑，比如移除长时间未活动的连接
            let stats = sse_manager.get_stats();
            info!(
                target = "udmin",
                total_connections = %stats.total_connections,
                authenticated_connections = %stats.authenticated_connections,
                unique_users = %stats.unique_users,
                "SSE connection stats"
            );
        }
    });
}
```

## 中间件组合和配置

### 中间件栈配置

```rust
use axum::{
    middleware,
    Router,
};
use std::sync::Arc;
use tower::ServiceBuilder;
use tower_http::{
    compression::CompressionLayer,
    timeout::TimeoutLayer,
    trace::TraceLayer,
};

use crate::{
    middlewares::{
        auth::{jwt_auth_middleware, optional_auth_middleware},
        cors::create_cors_layer,
        logging::{request_logging_middleware, performance_monitoring_middleware},
        rate_limit::{create_rate_limit_middleware, ip_rate_limit_middleware, user_rate_limit_middleware},
    },
    AppState,
};

/// 创建中间件栈
pub fn create_middleware_stack(state: AppState) -> ServiceBuilder<
    impl tower::Layer<
        axum::routing::Router,
        Service = impl tower::Service<
            http::Request<axum::body::Body>,
            Response = axum::response::Response,
            Error = std::convert::Infallible,
        > + Clone + Send + 'static,
    > + Clone,
> {
    // 创建限流器
    let rate_limiter = create_rate_limit_middleware(Default::default());
    
    ServiceBuilder::new()
        // 请求追踪
        .layer(TraceLayer::new_for_http())
        // 请求超时
        .layer(TimeoutLayer::new(std::time::Duration::from_secs(30)))
        // 响应压缩
        .layer(CompressionLayer::new())
        // CORS
        .layer(create_cors_layer(Default::default()))
        // 请求日志
        .layer(middleware::from_fn(request_logging_middleware))
        // 性能监控
        .layer(middleware::from_fn(performance_monitoring_middleware))
        // IP 限流
        .layer(middleware::from_fn_with_state(
            Arc::clone(&rate_limiter),
            ip_rate_limit_middleware,
        ))
        // 用户限流（需要在认证之后）
        .layer(middleware::from_fn_with_state(
            Arc::clone(&rate_limiter),
            user_rate_limit_middleware,
        ))
}

/// 为需要认证的路由创建中间件栈
pub fn create_auth_middleware_stack(state: AppState) -> ServiceBuilder<
    impl tower::Layer<
        axum::routing::Router,
        Service = impl tower::Service<
            http::Request<axum::body::Body>,
            Response = axum::response::Response,
            Error = std::convert::Infallible,
        > + Clone + Send + 'static,
    > + Clone,
> {
    ServiceBuilder::new()
        .layer(middleware::from_fn_with_state(
            state.clone(),
            jwt_auth_middleware,
        ))
}

/// 为可选认证的路由创建中间件栈
pub fn create_optional_auth_middleware_stack(state: AppState) -> ServiceBuilder<
    impl tower::Layer<
        axum::routing::Router,
        Service = impl tower::Service<
            http::Request<axum::body::Body>,
            Response = axum::response::Response,
            Error = std::convert::Infallible,
        > + Clone + Send + 'static,
    > + Clone,
> {
    ServiceBuilder::new()
        .layer(middleware::from_fn_with_state(
            state.clone(),
            optional_auth_middleware,
        ))
}
```

## 测试支持

### 中间件测试

```rust
#[cfg(test)]
mod tests {
    use super::*;
    use axum::{
        body::Body,
        http::{Request, StatusCode},
    };
    use tower::ServiceExt;
    
    #[tokio::test]
    async fn test_cors_middleware() {
        let app = Router::new()
            .route("/test", axum::routing::get(|| async { "OK" }))
            .layer(create_cors_layer(Default::default()));
        
        let request = Request::builder()
            .method("OPTIONS")
            .uri("/test")
            .header("Origin", "http://localhost:3000")
            .body(Body::empty())
            .unwrap();
        
        let response = app.oneshot(request).await.unwrap();
        
        assert_eq!(response.status(), StatusCode::OK);
        assert!(response.headers().contains_key("access-control-allow-origin"));
    }
    
    #[tokio::test]
    async fn test_rate_limit_middleware() {
        let rate_limiter = Arc::new(RateLimiter::new(1, 1)); // 1 token, 1 per second
        
        let app = Router::new()
            .route("/test", axum::routing::get(|| async { "OK" }))
            .layer(middleware::from_fn_with_state(
                rate_limiter,
                ip_rate_limit_middleware,
            ));
        
        // 第一个请求应该成功
        let request1 = Request::builder()
            .uri("/test")
            .body(Body::empty())
            .unwrap();
        
        let response1 = app.clone().oneshot(request1).await.unwrap();
        assert_eq!(response1.status(), StatusCode::OK);
        
        // 第二个请求应该被限流
        let request2 = Request::builder()
            .uri("/test")
            .body(Body::empty())
            .unwrap();
        
        let response2 = app.oneshot(request2).await.unwrap();
        assert_eq!(response2.status(), StatusCode::TOO_MANY_REQUESTS);
    }
}
```

## 最佳实践

### 中间件设计

- **单一职责**: 每个中间件只负责一个特定功能
- **可组合性**: 中间件可以灵活组合使用
- **性能优化**: 最小化中间件的性能开销
- **错误处理**: 优雅地处理中间件中的错误
- **日志记录**: 记录关键操作和错误信息

### 安全考虑

- **认证验证**: 严格验证用户身份
- **权限检查**: 确保用户有足够的权限
- **输入验证**: 验证所有输入数据
- **限流保护**: 防止恶意请求和DDoS攻击
- **CORS配置**: 正确配置跨域资源共享

### 性能优化

- **缓存策略**: 缓存认证结果和权限信息
- **连接池**: 合理配置数据库连接池
- **异步处理**: 使用异步操作提高并发性能
- **资源清理**: 及时清理过期的连接和资源

## 总结

中间件层是 UdminAI 系统的重要组成部分，提供了认证授权、请求日志、错误处理、CORS、WebSocket、SSE、限流等核心功能。通过模块化设计和灵活的组合机制，中间件层为系统提供了强大的横切关注点支持，确保了系统的安全性、可靠性和性能。

主要特点：

- **模块化设计**: 每个中间件独立实现，职责单一
- **灵活组合**: 支持灵活的中间件组合和配置
- **高性能**: 优化的实现确保最小的性能开销
- **类型安全**: 利用 Rust 类型系统确保安全性
- **实时通信**: 支持 WebSocket 和 SSE 实时通信
- **安全防护**: 提供认证、授权、限流等安全机制

通过这套完整的中间件系统，UdminAI 能够提供安全、高效、可靠的 Web 服务，满足企业级应用的各种需求。
```