refactor(proxy): Optimize hop-by-hop header handling and routing logic

- Simplify hop-by-hop headers initialization using map literal
- Create a local copy of hop headers to improve header filtering
- Enhance routing logic with context-based timeout for alternative target checks
- Improve error handling and logging in file size and routing detection
- Reduce unnecessary goroutine complexity in target URL selection

internal/handler/proxy.go

@@ -28,23 +28,20 @@ const (
 )
 
 // 添加 hop-by-hop 头部映射
-var hopHeadersMap = make(map[string]bool)
+var hopHeadersBase = map[string]bool{
+	"Connection":          true,
+	"Keep-Alive":          true,
+	"Proxy-Authenticate":  true,
+	"Proxy-Authorization": true,
+	"Proxy-Connection":    true,
+	"Te":                  true,
+	"Trailer":             true,
+	"Transfer-Encoding":   true,
+	"Upgrade":             true,
+}
 
 func init() {
-	headers := []string{
-		"Connection",
-		"Keep-Alive",
-		"Proxy-Authenticate",
-		"Proxy-Authorization",
-		"Proxy-Connection",
-		"Te",
-		"Trailer",
-		"Transfer-Encoding",
-		"Upgrade",
-	}
-	for _, h := range headers {
-		hopHeadersMap[h] = true
-	}
+	// 移除旧的初始化代码，因为我们直接在 map 字面量中定义了所有值
 }
 
 // ErrorHandler 定义错误处理函数类型
@@ -337,16 +334,22 @@ func (h *ProxyHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 }
 
 func copyHeader(dst, src http.Header) {
+	// 创建一个新的局部 map，复制基础 hop headers
+	hopHeaders := make(map[string]bool, len(hopHeadersBase))
+	for k, v := range hopHeadersBase {
+		hopHeaders[k] = v
+	}
+
 	// 处理 Connection 头部指定的其他 hop-by-hop 头部
 	if connection := src.Get("Connection"); connection != "" {
 		for _, h := range strings.Split(connection, ",") {
-			hopHeadersMap[strings.TrimSpace(h)] = true
+			hopHeaders[strings.TrimSpace(h)] = true
 		}
 	}
 
-	// 使用 map 快速查找，跳过 hop-by-hop 头部
+	// 使用局部 map 快速查找，跳过 hop-by-hop 头部
 	for k, vv := range src {
-		if !hopHeadersMap[k] {
+		if !hopHeaders[k] {
 			for _, v := range vv {
 				dst.Add(k, v)
 			}

internal/utils/utils.go

@@ -187,6 +187,20 @@ func GetTargetURL(client *http.Client, r *http.Request, pathConfig config.PathCo
 	// 默认使用默认目标
 	targetBase := pathConfig.DefaultTarget
 
+	// 如果配置了扩展名映射
+	if pathConfig.ExtensionMap != nil {
+		ext := strings.ToLower(filepath.Ext(path))
+		if ext != "" {
+			ext = ext[1:] // 移除开头的点
+			// 检查是否在扩展名映射中
+			if altTarget, exists := pathConfig.GetExtensionTarget(ext); exists {
+				// 检查文件大小
+				contentLength, err := GetFileSize(client, targetBase+path)
+				if err != nil {
+					log.Printf("[Route] %s -> %s (error getting size: %v)", path, targetBase, err)
+					return targetBase
+				}
+
 				// 如果没有设置最小阈值，使用默认值 500KB
 				minThreshold := pathConfig.SizeThreshold
 				if minThreshold <= 0 {
@@ -199,76 +213,59 @@ func GetTargetURL(client *http.Client, r *http.Request, pathConfig config.PathCo
 					maxThreshold = 10 * 1024 * 1024
 				}
 
-	// 检查文件扩展名
-	if pathConfig.ExtensionMap != nil {
-		ext := strings.ToLower(filepath.Ext(path))
-		if ext != "" {
-			ext = ext[1:] // 移除开头的点
-			// 先检查是否在扩展名映射中
-			if altTarget, exists := pathConfig.GetExtensionTarget(ext); exists {
-				// 使用 channel 来并发获取文件大小和检查可访问性
-				type result struct {
-					size       int64
+				if contentLength > minThreshold && contentLength <= maxThreshold {
+					// 创建一个带超时的 context
+					ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+					defer cancel()
+
+					// 使用 channel 来接收备用源检查结果
+					altChan := make(chan struct {
 						accessible bool
 						err        error
-				}
-				defaultChan := make(chan result, 1)
-				altChan := make(chan result, 1)
+					}, 1)
 
-				// 并发检查默认源和备用源
-				go func() {
-					size, err := GetFileSize(client, targetBase+path)
-					defaultChan <- result{size: size, err: err}
-				}()
+					// 在 goroutine 中检查备用源可访问性
 					go func() {
 						accessible := isTargetAccessible(client, altTarget+path)
-					altChan <- result{accessible: accessible}
+						select {
+						case altChan <- struct {
+							accessible bool
+							err        error
+						}{accessible: accessible}:
+						case <-ctx.Done():
+							// context 已取消，不需要发送结果
+						}
 					}()
 
-				// 获取默认源结果
-				defaultResult := <-defaultChan
-				if defaultResult.err != nil {
-					log.Printf("[FileSize] Failed to get size from default source for %s: %v", path, defaultResult.err)
-					return targetBase
-				}
-				contentLength := defaultResult.size
-				log.Printf("[FileSize] Path: %s, Size: %s (from default source)",
-					path, FormatBytes(contentLength))
-
-				// 检查文件大小是否在阈值范围内
-				if contentLength > minThreshold && contentLength <= maxThreshold {
-					// 获取备用源检查结果
-					altResult := <-altChan
-					if altResult.accessible {
+					// 等待结果或超时
+					select {
+					case result := <-altChan:
+						if result.accessible {
 							log.Printf("[Route] %s -> %s (size: %s > %s and <= %s)",
 								path, altTarget, FormatBytes(contentLength),
 								FormatBytes(minThreshold), FormatBytes(maxThreshold))
 							return altTarget
-					} else {
+						}
 						log.Printf("[Route] %s -> %s (fallback: alternative target not accessible)",
 							path, targetBase)
+					case <-ctx.Done():
+						log.Printf("[Route] %s -> %s (fallback: alternative target check timeout)",
+							path, targetBase)
 					}
 				} else if contentLength <= minThreshold {
-					// 如果文件大小不合适，直接丢弃备用源检查结果
-					go func() { <-altChan }()
 					log.Printf("[Route] %s -> %s (size: %s <= %s)",
 						path, targetBase, FormatBytes(contentLength), FormatBytes(minThreshold))
 				} else {
-					// 如果文件大小不合适，直接丢弃备用源检查结果
-					go func() { <-altChan }()
 					log.Printf("[Route] %s -> %s (size: %s > %s)",
 						path, targetBase, FormatBytes(contentLength), FormatBytes(maxThreshold))
 				}
 			} else {
-				// 记录没有匹配扩展名映射的情况
 				log.Printf("[Route] %s -> %s (no extension mapping)", path, targetBase)
 			}
 		} else {
-			// 记录没有扩展名的情况
 			log.Printf("[Route] %s -> %s (no extension)", path, targetBase)
 		}
 	} else {
-		// 记录没有扩展名映射配置的情况
 		log.Printf("[Route] %s -> %s (no extension map)", path, targetBase)
 	}