import { Buffer } from "node:buffer";

/** Bounded newline frames, including a final frame without a newline. */
export async function* lines(reader: ReadableStreamDefaultReader<Uint8Array>) {
  const limit = 16 * 1024 * 1024;
  let buffered = "";
  const decoder = new TextDecoder("utf-8");
  while (true) {
    const { done, value } = await reader.read();
    if (done) break;
    buffered += decoder.decode(value, { stream: true });
    let newline: number;
    while ((newline = buffered.indexOf("\n")) >= 0) {
      const line = buffered.slice(0, newline);
      if (Buffer.byteLength(line) > limit) throw new Error("MCP frame exceeds 16 MiB");
      buffered = buffered.slice(newline + 1);
      if (line.trim()) yield line;
    }
    if (Buffer.byteLength(buffered) > limit) throw new Error("MCP frame exceeds 16 MiB");
  }
  buffered += decoder.decode();
  if (buffered.trim()) yield buffered;
}