From 3a17e543c5ed7f4b3d10c41c77909126a860f1ee Mon Sep 17 00:00:00 2001
From: Zac Gaetano <zgaetano@wilddragon.net>
Date: Fri, 17 Apr 2026 08:44:59 -0400
Subject: [PATCH] feat(webrtc): add thread-safe Registry for stream_id ->
 SourceHandle

---
 core/webrtc/registry.go      | 51 +++++++++++++++++++++++++
 core/webrtc/registry_test.go | 74 ++++++++++++++++++++++++++++++++++++
 2 files changed, 125 insertions(+)
 create mode 100644 core/webrtc/registry.go
 create mode 100644 core/webrtc/registry_test.go

diff --git a/core/webrtc/registry.go b/core/webrtc/registry.go
new file mode 100644
index 0000000..fd924b2
--- /dev/null
+++ b/core/webrtc/registry.go
@@ -0,0 +1,51 @@
+package webrtc
+
+import (
+	"fmt"
+	"sync"
+)
+
+// SourceHandle is the minimal interface the Registry stores per stream_id.
+// The concrete type is *Source, defined in source.go.
+type SourceHandle interface {
+	ID() string
+}
+
+// Registry is a thread-safe map from stream_id to active SourceHandle.
+type Registry struct {
+	mu      sync.RWMutex
+	streams map[string]SourceHandle
+}
+
+// NewRegistry returns an empty Registry.
+func NewRegistry() *Registry {
+	return &Registry{streams: make(map[string]SourceHandle)}
+}
+
+// Register associates src with streamID. Returns an error if streamID is
+// already registered.
+func (r *Registry) Register(streamID string, src SourceHandle) error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if _, exists := r.streams[streamID]; exists {
+		return fmt.Errorf("webrtc: stream %q already registered", streamID)
+	}
+	r.streams[streamID] = src
+	return nil
+}
+
+// Lookup returns the handle for streamID. The second return value is false
+// if no source is registered.
+func (r *Registry) Lookup(streamID string) (SourceHandle, bool) {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	src, ok := r.streams[streamID]
+	return src, ok
+}
+
+// Deregister removes streamID. No-op if not present.
+func (r *Registry) Deregister(streamID string) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	delete(r.streams, streamID)
+}
diff --git a/core/webrtc/registry_test.go b/core/webrtc/registry_test.go
new file mode 100644
index 0000000..543777e
--- /dev/null
+++ b/core/webrtc/registry_test.go
@@ -0,0 +1,74 @@
+package webrtc
+
+import (
+	"sync"
+	"testing"
+)
+
+// mockSource implements the minimum Source-like shape needed by the registry.
+// The real Source type is defined in Task 5; the registry only needs a
+// stable type to store and retrieve.
+type mockSource struct {
+	id string
+}
+
+func (m *mockSource) ID() string { return m.id }
+
+func TestRegistry_RegisterAndLookup(t *testing.T) {
+	r := NewRegistry()
+	src := &mockSource{id: "streamA"}
+
+	if err := r.Register("streamA", src); err != nil {
+		t.Fatalf("Register returned error: %v", err)
+	}
+
+	got, ok := r.Lookup("streamA")
+	if !ok {
+		t.Fatal("Lookup(streamA) returned ok=false, want true")
+	}
+	if got != src {
+		t.Errorf("Lookup returned %v, want %v", got, src)
+	}
+}
+
+func TestRegistry_LookupMissing(t *testing.T) {
+	r := NewRegistry()
+	_, ok := r.Lookup("nope")
+	if ok {
+		t.Error("Lookup on empty registry returned ok=true, want false")
+	}
+}
+
+func TestRegistry_DuplicateRegister(t *testing.T) {
+	r := NewRegistry()
+	_ = r.Register("streamA", &mockSource{id: "streamA"})
+
+	if err := r.Register("streamA", &mockSource{id: "streamA"}); err == nil {
+		t.Error("duplicate Register should return error, got nil")
+	}
+}
+
+func TestRegistry_Deregister(t *testing.T) {
+	r := NewRegistry()
+	_ = r.Register("streamA", &mockSource{id: "streamA"})
+	r.Deregister("streamA")
+
+	if _, ok := r.Lookup("streamA"); ok {
+		t.Error("after Deregister, Lookup should return ok=false")
+	}
+}
+
+func TestRegistry_ConcurrentAccess(t *testing.T) {
+	r := NewRegistry()
+	var wg sync.WaitGroup
+
+	for i := 0; i < 100; i++ {
+		wg.Add(3)
+		id := string(rune('a' + (i % 26)))
+		go func() { defer wg.Done(); _ = r.Register(id, &mockSource{id: id}) }()
+		go func() { defer wg.Done(); _, _ = r.Lookup(id) }()
+		go func() { defer wg.Done(); r.Deregister(id) }()
+	}
+	wg.Wait()
+	// No assertion — test passes if -race doesn't flag anything.
+}