feat(proxy): add error mapper for HTTP status code mapping

- Add error_mapper.rs module to map ProxyError to HTTP status codes
- Implement map_proxy_error_to_status() for error classification
- Implement get_error_message() for user-friendly error messages
- Support all error types: upstream, timeout, connection, provider failures
- Include comprehensive unit tests for all mappings

src-tauri/src/proxy/error_mapper.rs

@@ -0,0 +1,110 @@
+//! 错误类型到 HTTP 状态码的映射
+//!
+//! 将 ProxyError 映射到合适的 HTTP 状态码，用于日志记录
+
+use super::ProxyError;
+
+/// 将 ProxyError 映射到 HTTP 状态码
+///
+/// 映射规则：
+/// - 上游错误：直接使用上游返回的状态码
+/// - 超时：504 Gateway Timeout
+/// - 连接失败：502 Bad Gateway
+/// - 无可用 Provider：503 Service Unavailable
+/// - 重试耗尽：503 Service Unavailable
+/// - 其他错误：500 Internal Server Error
+pub fn map_proxy_error_to_status(error: &ProxyError) -> u16 {
+    match error {
+        // 上游错误：使用实际状态码
+        ProxyError::UpstreamError { status, .. } => *status,
+
+        // 超时错误：504 Gateway Timeout
+        ProxyError::Timeout(_) => 504,
+
+        // 转发失败/连接失败：502 Bad Gateway
+        ProxyError::ForwardFailed(_) => 502,
+
+        // 无可用 Provider：503 Service Unavailable
+        ProxyError::NoAvailableProvider => 503,
+
+        // 重试耗尽：503 Service Unavailable
+        ProxyError::MaxRetriesExceeded => 503,
+
+        // Provider 不健康：503 Service Unavailable
+        ProxyError::ProviderUnhealthy(_) => 503,
+
+        // 数据库错误：500 Internal Server Error
+        ProxyError::DatabaseError(_) => 500,
+
+        // 转换错误：500 Internal Server Error
+        ProxyError::TransformError(_) => 500,
+
+        // 其他未知错误：500 Internal Server Error
+        _ => 500,
+    }
+}
+
+/// 将 ProxyError 转换为用户友好的错误消息
+pub fn get_error_message(error: &ProxyError) -> String {
+    match error {
+        ProxyError::UpstreamError { status, body } => {
+            if let Some(body) = body {
+                format!("上游错误 ({status}): {body}")
+            } else {
+                format!("上游错误 ({status})")
+            }
+        }
+        ProxyError::Timeout(msg) => format!("请求超时: {msg}"),
+        ProxyError::ForwardFailed(msg) => format!("转发失败: {msg}"),
+        ProxyError::NoAvailableProvider => "无可用 Provider".to_string(),
+        ProxyError::MaxRetriesExceeded => "所有 Provider 都失败，重试耗尽".to_string(),
+        ProxyError::ProviderUnhealthy(msg) => format!("Provider 不健康: {msg}"),
+        ProxyError::DatabaseError(msg) => format!("数据库错误: {msg}"),
+        ProxyError::TransformError(msg) => format!("请求/响应转换错误: {msg}"),
+        _ => error.to_string(),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_map_upstream_error() {
+        let error = ProxyError::UpstreamError {
+            status: 401,
+            body: Some("Unauthorized".to_string()),
+        };
+        assert_eq!(map_proxy_error_to_status(&error), 401);
+    }
+
+    #[test]
+    fn test_map_timeout_error() {
+        let error = ProxyError::Timeout("Request timeout".to_string());
+        assert_eq!(map_proxy_error_to_status(&error), 504);
+    }
+
+    #[test]
+    fn test_map_connection_error() {
+        let error = ProxyError::ForwardFailed("Connection refused".to_string());
+        assert_eq!(map_proxy_error_to_status(&error), 502);
+    }
+
+    #[test]
+    fn test_map_no_provider_error() {
+        let error = ProxyError::NoAvailableProvider;
+        assert_eq!(map_proxy_error_to_status(&error), 503);
+    }
+
+    #[test]
+    fn test_get_error_message() {
+        let error = ProxyError::UpstreamError {
+            status: 500,
+            body: Some("Internal Server Error".to_string()),
+        };
+        let msg = get_error_message(&error);
+        assert!(msg.contains("上游错误"));
+        assert!(msg.contains("500"));
+        assert!(msg.contains("Internal Server Error"));
+    }
+}

src-tauri/src/proxy/mod.rs

@@ -4,6 +4,7 @@
 
 pub mod circuit_breaker;
 pub mod error;
+pub mod error_mapper;
 mod forwarder;
 mod handlers;
 mod health;