feat: support arbitrary URL proxy via single token

Allow proxying to any URL through the single-token auth path:
- /TOKEN/https://target.com/path
- /TOKEN/https:/target.com/path (browser-normalized)
- /TOKEN/target.com/path (auto-prefixed with https:// for known domains)

Also fix single-mode path handling that previously dropped
parts[2] when SplitN produced 3 parts.

via [HAPI](https://hapi.run)

Co-Authored-By: HAPI <[email protected]>

cmd/main.go

@@ -16,6 +16,80 @@ import (
 	"mirror-proxy/internal/proxy"
 )
 
+import (
+	"net/url"
+)
+
+// extractTargetURL 从请求路径中提取目标 URL
+// 支持格式: /https://target.com/path 或 /http://target.com/path 或 /target.com/path
+// 如果匹配，修改 r.URL.Path 为目标路径并返回目标 URL
+func extractTargetURL(r *http.Request) (string, bool) {
+	path := strings.TrimPrefix(r.URL.Path, "/")
+
+	// 完整 URL 格式: https://... 或 http://...
+	if strings.HasPrefix(path, "https://") {
+		u, err := url.Parse(path)
+		if err == nil {
+			r.URL.Path = u.Path
+			if u.RawQuery != "" {
+				r.URL.RawQuery = u.RawQuery
+			}
+			return path, true
+		}
+	}
+	if strings.HasPrefix(path, "http://") {
+		u, err := url.Parse(path)
+		if err == nil {
+			r.URL.Path = u.Path
+			if u.RawQuery != "" {
+				r.URL.RawQuery = u.RawQuery
+			}
+			return path, true
+		}
+	}
+
+	// 浏览器规范化后的格式: https:/... 或 http:/...
+	if strings.HasPrefix(path, "https:/") {
+		targetURL := "https://" + strings.TrimPrefix(path, "https:/")
+		u, err := url.Parse(targetURL)
+		if err == nil {
+			r.URL.Path = u.Path
+			if u.RawQuery != "" {
+				r.URL.RawQuery = u.RawQuery
+			}
+			return targetURL, true
+		}
+	}
+	if strings.HasPrefix(path, "http:/") {
+		targetURL := "http://" + strings.TrimPrefix(path, "http:/")
+		u, err := url.Parse(targetURL)
+		if err == nil {
+			r.URL.Path = u.Path
+			if u.RawQuery != "" {
+				r.URL.RawQuery = u.RawQuery
+			}
+			return targetURL, true
+		}
+	}
+
+	// 无协议前缀的域名
+	if strings.HasPrefix(path, "github.com/") ||
+		strings.HasPrefix(path, "raw.githubusercontent.com/") ||
+		strings.HasPrefix(path, "api.github.com/") {
+		targetURL := "https://" + path
+		u, err := url.Parse(targetURL)
+		if err == nil {
+			r.URL.Path = u.Path
+			if u.RawQuery != "" {
+				r.URL.RawQuery = u.RawQuery
+			}
+			return targetURL, true
+		}
+	}
+
+	return "", false
+}
+
 func buildHandler(cfg *config.Config) (*admin.Handler, http.Handler) {
 	rl := auth.NewRateLimiter()
 	adminHandler := admin.NewHandler(cfg)
@@ -78,6 +152,12 @@ func buildHandler(cfg *config.Config) (*admin.Handler, http.Handler) {
 			return
 		}
 
+		// URL 代理模式: /https://target.com/path 或 /target.com/path
+		if targetURL, isURL := extractTargetURL(r); isURL {
+			proxy.DynamicProxy(targetURL).ServeHTTP(w, r)
+			return
+		}
+
 		switch link.Type {
 		case "docker":
 			dockerProxy.ServeHTTP(w, r)