Sub2API v1.0 - AI API 网关（二开初始版本，基于上游 Wei-Shaw/sub2api）

backend/internal/handler/concurrency_error_response.go

@@ -0,0 +1,33 @@
+package handler
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+)
+
+const statusClientClosedRequest = 499
+
+func concurrencyErrorResponse(err error, slotType string) (int, string, string) {
+	var waitQueueFullErr *WaitQueueFullError
+	if errors.As(err, &waitQueueFullErr) {
+		return http.StatusTooManyRequests, "rate_limit_error",
+			"Too many pending requests, please retry later"
+	}
+
+	var concurrencyErr *ConcurrencyError
+	if errors.As(err, &concurrencyErr) {
+		if concurrencyErr.SlotType != "" {
+			slotType = concurrencyErr.SlotType
+		}
+		return http.StatusTooManyRequests, "rate_limit_error",
+			fmt.Sprintf("Concurrency limit exceeded for %s, please retry later", slotType)
+	}
+
+	if errors.Is(err, context.Canceled) {
+		return statusClientClosedRequest, "api_error", "context canceled"
+	}
+
+	return http.StatusServiceUnavailable, "api_error", "Service temporarily unavailable, please retry later"
+}