// fsproxy 执行子进程:从 stdin 读一条 JSON 请求,执行单个文件操作,stdout 逐行 JSON 上报
// {t:"hb",phase,bytes,total}(按 progressIntervalMs 节流,阶段切换与阶段完成立即报)/ {t:"ok",result} / {t:"err",code,message}。
// SIGTERM → 中止当前操作(copy 会清掉自己的 partial)后退出;挂死在系统调用里时由父进程 SIGKILL 回收。
// 只依赖 node 内置模块,`deno run --no-config` 毫秒级启动。编译二进制可在入口按 --role fsworker 调 fsWorkerMain()。
import { toFsError } from "./errors.ts";
import { type FsOpRequest, type FsProgress, runFsOp } from "./fsops.ts";

const enc = new TextEncoder();

function send(obj: unknown): void {
  try {
    Deno.stdout.writeSync(enc.encode(`${JSON.stringify(obj)}\n`));
  } catch {
    // 父进程已退出:无处可报
  }
}

/** 阻塞 JS 线程(测试用,模拟卡死的系统调用:信号监听器也不会运行) */
function blockForever(): never {
  const a = new Int32Array(new SharedArrayBuffer(4));
  for (;;) Atomics.wait(a, 0, 0);
}

export async function fsWorkerMain(progressIntervalMs = Number(Deno.env.get("UMT_FS_PROGRESS_INTERVAL_MS") ?? 1000)) {
  const req = JSON.parse(await new Response(Deno.stdin.readable).text()) as FsOpRequest;
  const ac = new AbortController();
  Deno.addSignalListener("SIGTERM", () => {
    if (req._test?.ignoreTerm) return;
    ac.abort();
    // 操作卡在系统调用里时 abort 解不开:给清理一点时间后直接退出
    setTimeout(() => Deno.exit(143), 500);
  });
  let lastAt = 0;
  let lastPhase = "";
  const progress = (p: FsProgress) => {
    const hang = req._test?.hangAfterBytes;
    const now = Date.now();
    // 阶段切换、阶段完成(bytes 到 total)立即报,其余按间隔节流——否则最后一跳可能被节流吞掉
    const phaseDone = p.total > 0 && p.bytes >= p.total;
    if (
      p.phase !== lastPhase ||
      phaseDone ||
      now - lastAt >= progressIntervalMs ||
      (hang !== undefined && p.bytes >= hang)
    ) {
      lastAt = now;
      lastPhase = p.phase;
      send({ t: "hb", ...p });
    }
    if (hang !== undefined && p.bytes >= hang) blockForever();
  };
  if (req._test?.hangAfterBytes === 0) {
    send({ t: "hb", phase: "start", bytes: 0, total: 0 });
    blockForever();
  }
  try {
    const result = await runFsOp(req, { signal: ac.signal, progress });
    send({ t: "ok", result });
  } catch (e) {
    const fe = toFsError(e);
    send({
      t: "err",
      code: ac.signal.aborted ? "ABORTED" : fe.code,
      message: fe.message,
      ...(fe.detail.path ? { path: fe.detail.path } : {}),
      ...(fe.detail.syscall ? { syscall: fe.detail.syscall } : {}),
    });
  }
  Deno.exit(0);
}

if (import.meta.main) await fsWorkerMain();