refactor(core): canonicalize pty service (#32182)

packages/core/src/pty/protocol.ts

@@ -0,0 +1,37 @@
+export * as PtyProtocol from "./protocol"
+
+// Wire protocol for PTY websocket transports. The PTY domain service is transport-free; server
+// routes adapt Pty.attach to websockets with these helpers so every surface speaks one protocol.
+//
+// Outbound frames are raw UTF-8 terminal chunks. One control frame — a 0x00 byte followed by
+// UTF-8 JSON — carries the absolute output cursor after replay so clients can resume later.
+
+const encoder = new TextEncoder()
+const decoder = new TextDecoder("utf-8", { fatal: true })
+
+// Replay can be megabytes; send it in bounded frames.
+export const REPLAY_CHUNK = 64 * 1024
+
+export function metaFrame(cursor: number) {
+  const bytes = encoder.encode(JSON.stringify({ cursor }))
+  const out = new Uint8Array(bytes.length + 1)
+  out[0] = 0
+  out.set(bytes, 1)
+  return out
+}
+
+export function chunks(data: string) {
+  const out: string[] = []
+  for (let i = 0; i < data.length; i += REPLAY_CHUNK) out.push(data.slice(i, i + REPLAY_CHUNK))
+  return out
+}
+
+// Inbound client frames are UTF-8 text or binary; invalid UTF-8 input is dropped.
+export function decodeInput(message: string | Uint8Array | ArrayBuffer) {
+  if (typeof message === "string") return message
+  try {
+    return decoder.decode(message instanceof ArrayBuffer ? new Uint8Array(message) : message)
+  } catch {
+    return undefined
+  }
+}