feat: deduplicate proxy token creation

internal/playback/proxy_tokens_test.go

@@ -0,0 +1,68 @@
+package playback
+
+import (
+	"testing"
+	"time"
+)
+
+func TestProxyTokenStoreReusesUnexpiredTokenForSameTarget(t *testing.T) {
+	store := newProxyTokenStore()
+	now := time.Date(2026, 6, 16, 12, 0, 0, 0, time.UTC)
+
+	first, err := store.create("https://cdn.example.test/seg.ts", "https://referer.example.test", "stream", time.Hour, now)
+	if err != nil {
+		t.Fatalf("create first token: %v", err)
+	}
+	second, err := store.create("https://cdn.example.test/seg.ts", "https://referer.example.test", "stream", time.Hour, now.Add(time.Minute))
+	if err != nil {
+		t.Fatalf("create second token: %v", err)
+	}
+
+	if first != second {
+		t.Fatalf("tokens differ for same target: %q != %q", first, second)
+	}
+	if len(store.tokens) != 1 {
+		t.Fatalf("token count = %d, want 1", len(store.tokens))
+	}
+}
+
+func TestProxyTokenStoreCreatesNewTokenAfterExpiry(t *testing.T) {
+	store := newProxyTokenStore()
+	now := time.Date(2026, 6, 16, 12, 0, 0, 0, time.UTC)
+
+	first, err := store.create("https://cdn.example.test/seg.ts", "https://referer.example.test", "stream", time.Hour, now)
+	if err != nil {
+		t.Fatalf("create first token: %v", err)
+	}
+	second, err := store.create("https://cdn.example.test/seg.ts", "https://referer.example.test", "stream", time.Hour, now.Add(time.Hour))
+	if err != nil {
+		t.Fatalf("create second token: %v", err)
+	}
+
+	if first == second {
+		t.Fatalf("token was reused after expiry: %q", first)
+	}
+	if len(store.tokens) != 1 {
+		t.Fatalf("token count = %d, want 1", len(store.tokens))
+	}
+}
+
+func TestProxyTokenStoreCleansReverseIndexOnResolveExpiry(t *testing.T) {
+	store := newProxyTokenStore()
+	now := time.Date(2026, 6, 16, 12, 0, 0, 0, time.UTC)
+
+	token, err := store.create("https://cdn.example.test/seg.ts", "https://referer.example.test", "stream", time.Hour, now)
+	if err != nil {
+		t.Fatalf("create token: %v", err)
+	}
+	if _, err := store.resolve(token, now.Add(time.Hour)); err == nil {
+		t.Fatal("resolve expired token unexpectedly succeeded")
+	}
+
+	if len(store.tokens) != 0 {
+		t.Fatalf("token count = %d, want 0", len(store.tokens))
+	}
+	if len(store.byTarget) != 0 {
+		t.Fatalf("target index count = %d, want 0", len(store.byTarget))
+	}
+}