From 7ae31d0ec96ef3d5cfdfffdcd7f2e480a59b5408 Mon Sep 17 00:00:00 2001
From: Juliusz Chroboczek <jch@irif.fr>
Date: Mon, 13 Jan 2025 15:11:44 +0100
Subject: [PATCH 1/2] Make Registry.Build take extra interceptors

Make Registry.Build take an optional list of extra interceptors
that are added before the ones specified by the registry.
---
 registry.go | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/registry.go b/registry.go
index e36ef6bf..e9451961 100644
--- a/registry.go
+++ b/registry.go
@@ -14,12 +14,17 @@ func (r *Registry) Add(f Factory) {
 }
 
 // Build constructs a single Interceptor from a InterceptorRegistry
-func (r *Registry) Build(id string) (Interceptor, error) {
+// The extra interceptors are added to the chain before the ones specified
+// by the registry.
+func (r *Registry) Build(id string, extra... Interceptor) (Interceptor, error) {
 	if len(r.factories) == 0 {
 		return &NoOp{}, nil
 	}
 
 	interceptors := []Interceptor{}
+
+	interceptors = append(interceptors, extra...)
+
 	for _, f := range r.factories {
 		i, err := f.NewInterceptor(id)
 		if err != nil {

From 888fadd4e4cbaac42663b392f6f9e9b8d50da67e Mon Sep 17 00:00:00 2001
From: Juliusz Chroboczek <jch@irif.fr>
Date: Mon, 13 Jan 2025 16:18:41 +0100
Subject: [PATCH 2/2] Implement cc.NewSingleInterceptor

Creates a single interceptor without going through a factory.
---
 pkg/cc/interceptor.go | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/pkg/cc/interceptor.go b/pkg/cc/interceptor.go
index 252ab29f..5d8da82d 100644
--- a/pkg/cc/interceptor.go
+++ b/pkg/cc/interceptor.go
@@ -61,11 +61,25 @@ func (f *InterceptorFactory) OnNewPeerConnection(cb NewPeerConnectionCallback) {
 }
 
 // NewInterceptor returns a new CC interceptor
+// Don't call this, call [NewSingleInterceptor] instead.
 func (f *InterceptorFactory) NewInterceptor(id string) (interceptor.Interceptor, error) {
 	bwe, err := f.bweFactory()
 	if err != nil {
 		return nil, err
 	}
+	i, err := NewSingleInterceptor(bwe, f.opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	if f.addPeerConnection != nil {
+		f.addPeerConnection(id, i.estimator)
+	}
+	return i, nil
+}
+
+// NewSingleInterceptor returns a new CC interceptor
+func NewSingleInterceptor(bwe BandwidthEstimator, options ...Option) (*Interceptor, error) {
 	i := &Interceptor{
 		NoOp:      interceptor.NoOp{},
 		estimator: bwe,
@@ -73,15 +87,11 @@ func (f *InterceptorFactory) NewInterceptor(id string) (interceptor.Interceptor,
 		close:     make(chan struct{}),
 	}
 
-	for _, opt := range f.opts {
+	for _, opt := range options {
 		if err := opt(i); err != nil {
 			return nil, err
 		}
 	}
-
-	if f.addPeerConnection != nil {
-		f.addPeerConnection(id, i.estimator)
-	}
 	return i, nil
 }