/** CommandCode streams NDJSON; tolerate SSE-style `data:` prefixes and `[DONE]` sentinels. */
import { debugWhen, isDebugEnabled } from "./log.js";

export async function* iterateEvents(
  body: ReadableStream<Uint8Array>,
  dbg: boolean = isDebugEnabled(),
): AsyncGenerator<Record<string, any>> {
  const reader = body.getReader();
  const decoder = new TextDecoder();
  let buffer = "";

  try {
    while (true) {
      const { done, value } = await reader.read();
      if (done) break;
      buffer += decoder.decode(value, { stream: true });

      let newline: number;
      while ((newline = buffer.indexOf("\n")) >= 0) {
        const raw = buffer.slice(0, newline);
        buffer = buffer.slice(newline + 1);
        const event = parseLine(raw, dbg);
        if (event) yield event;
      }
    }

    // flush any trailing line without a newline
    buffer += decoder.decode();
    if (buffer.trim()) {
      const event = parseLine(buffer, dbg);
      if (event) yield event;
    }
  } finally {
    reader.releaseLock();
  }
}

function parseLine(raw: string, dbg: boolean): Record<string, any> | null {
  let line = raw.trim();
  if (!line || line.startsWith(":") || line.startsWith("event:")) return null;
  if (line.startsWith("data:")) line = line.slice(5).trim();
  if (!line || line === "[DONE]") return null;
  try {
    const parsed = JSON.parse(line);
    return parsed && typeof parsed === "object" ? parsed : null;
  } catch {
    debugWhen(dbg, "events", "parse-skip", `line=${line.slice(0, 512)}`);
    return null;
  }
}