import { existsSync } from "node:fs";
import { readFile } from "node:fs/promises";

async function sleep(ms: number) {
  await new Promise((resolve) => setTimeout(resolve, ms));
}

export async function monitorRun(input: {
  eventsPath: string;
  resultPath: string;
  onEvent?: (event: any) => void;
  pollMs?: number;
}) {
  const pollMs = input.pollMs ?? 50;
  let offset = 0;

  while (true) {
    if (existsSync(input.eventsPath)) {
      const text = await readFile(input.eventsPath, "utf8");
      const next = text.slice(offset);
      offset = text.length;

      for (const line of next.split("\n").filter(Boolean)) {
        input.onEvent?.(JSON.parse(line));
      }
    }

    if (existsSync(input.resultPath)) {
      return JSON.parse(await readFile(input.resultPath, "utf8"));
    }

    await sleep(pollMs);
  }
}