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

backend/internal/service/gateway_request_pricing.go

@@ -0,0 +1,55 @@
+package service
+
+import (
+	"context"
+	"time"
+
+	"github.com/Wei-Shaw/sub2api/internal/pkg/ctxkey"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/timezone"
+)
+
+type gatewayTokenRequestPricingAtCtxKey struct{}
+type gatewayTokenRequestBillingGroupCtxKey struct{}
+
+// WithGatewayTokenRequestPricing marks a shared-gateway request as token billed
+// and freezes the downstream pricing instant for its whole lifetime. Media and
+// metadata-only handlers deliberately do not call this helper.
+func WithGatewayTokenRequestPricing(ctx context.Context) (context.Context, time.Time) {
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	pricingAt := timezone.Now()
+	ctx = context.WithValue(ctx, gatewayTokenRequestPricingAtCtxKey{}, pricingAt)
+	// 调度过程中可能因 fallback/composite 路由覆盖 ctxkey.Group；计费 D 仍必须
+	// 使用认证时刻的父分组，和最终 RecordUsage 的计费归属保持一致。
+	if group, ok := ctx.Value(ctxkey.Group).(*Group); ok && IsGroupContextValid(group) {
+		ctx = context.WithValue(ctx, gatewayTokenRequestBillingGroupCtxKey{}, group)
+	}
+	return ctx, pricingAt
+}
+
+func gatewayTokenRequestPricingAtFromContext(ctx context.Context) (time.Time, bool) {
+	if ctx == nil {
+		return time.Time{}, false
+	}
+	pricingAt, ok := ctx.Value(gatewayTokenRequestPricingAtCtxKey{}).(time.Time)
+	return pricingAt, ok && !pricingAt.IsZero()
+}
+
+// GatewayTokenRequestPricingAtFromContext exposes the frozen instant to
+// handlers before they detach asynchronous usage-recording work.
+func GatewayTokenRequestPricingAtFromContext(ctx context.Context) time.Time {
+	pricingAt, _ := gatewayTokenRequestPricingAtFromContext(ctx)
+	return pricingAt
+}
+
+func gatewayTokenRequestBillingGroupFromContext(ctx context.Context) *Group {
+	if ctx == nil {
+		return nil
+	}
+	group, _ := ctx.Value(gatewayTokenRequestBillingGroupCtxKey{}).(*Group)
+	if IsGroupContextValid(group) {
+		return group
+	}
+	return nil
+}