[nfc] STW refactor and cleanup

src/workerd/io/trace-stream.h

@@ -55,51 +55,6 @@ class TailStreamCustomEventImpl final: public WorkerInterface::CustomEvent {
   uint16_t typeId;
 };
 
-// The TailStreamWriterState holds the current client-side state for a collection
-// of streaming tail workers that a worker is reporting events to.
-struct TailStreamWriterState {
-  // The initial state of our tail worker writer is that it is pending the first
-  // onset event. During this time we will only have a collection of WorkerInterface
-  // instances. When our first event is reported (the onset) we will arrange to acquire
-  // tailStream capabilities from each then use those to report the initial onset.
-  using Pending = kj::Array<kj::Own<WorkerInterface>>;
-
-  // Instances of Active are refcounted. The TailStreamWriterState itself
-  // holds the initial ref. Whenever events are being dispatched, an additional
-  // ref will be held by the outstanding pump promise in order to keep the
-  // client stub alive long enough for the rpc calls to complete. It is possible
-  // that the TailStreamWriterState will be dropped while pump promises are still
-  // pending.
-  struct Active: public kj::Refcounted {
-    // Reference to keep the worker interface instance alive.
-    kj::Maybe<rpc::TailStreamTarget::Client> capability;
-    bool pumping = false;
-    bool onsetSeen = false;
-    workerd::util::Queue<tracing::TailEvent> queue;
-
-    Active(rpc::TailStreamTarget::Client capability): capability(kj::mv(capability)) {}
-  };
-
-  struct Closed {};
-
-  // The closing flag will be set when the Outcome event has been reported.
-  // Once closing is true, no further events will be accepted and the state
-  // will transition to closed once the currently active pump completes.
-  bool closing = false;
-  kj::OneOf<Pending, kj::Array<kj::Own<Active>>, Closed> inner;
-  kj::TaskSet& waitUntilTasks;
-
-  TailStreamWriterState(Pending pending, kj::TaskSet& waitUntilTasks)
-      : inner(kj::mv(pending)),
-        waitUntilTasks(waitUntilTasks) {}
-  KJ_DISALLOW_COPY_AND_MOVE(TailStreamWriterState);
-
-  void reportImpl(tracing::TailEvent&& event);
-
-  // Delivers the queued tail events to a streaming tail worker.
-  kj::Promise<void> pump(kj::Own<Active> current);
-};
-
 kj::Maybe<kj::Own<tracing::TailStreamWriter>> initializeTailStreamWriter(
     kj::Array<kj::Own<WorkerInterface>> streamingTailWorkers, kj::TaskSet& waitUntilTasks);