// 沙箱调用(docs/adr/ADR-005-sandbox.md):每次一个子进程,权限全部撤销;超时 SIGKILL,子进程实际内存(RSS)超限 SIGKILL。
// 起子进程方式同 fsproxy:deno CLI → `deno run worker.ts`(开发 / 测试);编译二进制 → `<自身> --role sandbox`。
// 起不来(权限 / 运行时不支持)时退回进程内执行并记日志:仍有超时,但卡死的同步代码无法收回(只在本机调试时出现)。
import { basename } from "node:path";
import { fileURLToPath } from "node:url";
import { prepareJobs, SANDBOX_JOBS, type SandboxInput, type SandboxJobName, type SandboxOutput } from "./jobs.ts";

export type SandboxErrorKind = "timeout" | "memory" | "crash" | "job" | "spawn";

export class SandboxError extends Error {
  constructor(
    readonly kind: SandboxErrorKind,
    message: string,
  ) {
    super(message);
    this.name = "SandboxError";
  }
}

export interface SandboxOptions {
  /** 缺省 20 s */
  timeoutMs?: number;
  /** 子进程内存上限,缺省 512 MB */
  memoryMb?: number;
  signal?: AbortSignal;
}

const WORKER_PATH = fileURLToPath(new URL("./worker.ts", import.meta.url));
let inProcessReason: string | null = null;
const stats = { spawned: 0, timeouts: 0, memoryKills: 0, crashes: 0 };

export function sandboxStats() {
  return { ...stats, inProcessReason };
}

function command(memoryMb: number): { cmd: string; args: string[] } {
  const exe = Deno.execPath();
  if (/^deno(\.exe)?$/.test(basename(exe)))
    return {
      cmd: exe,
      args: [
        "run",
        "-A",
        "--quiet",
        "--no-prompt", // V8 堆上限只作兜底(设为两倍):主要靠下面的 RSS 看门狗,编译产物不认 V8 参数,两种模式一致
        `--v8-flags=--max-old-space-size=${memoryMb * 2}`,
        WORKER_PATH,
      ],
    };
  return { cmd: exe, args: ["--role", "sandbox"] };
}

/** 子进程实际内存(KB);读不到返回 null */
async function rssKb(pid: number): Promise<number | null> {
  try {
    const s = await Deno.readTextFile(`/proc/${pid}/status`);
    const m = /VmRSS:\s+(\d+)\s+kB/.exec(s);
    return m ? Number(m[1]) : null;
  } catch {
    return null;
  }
}

export async function runSandbox<J extends SandboxJobName>(
  job: J,
  input: SandboxInput<J>,
  opts: SandboxOptions = {},
): Promise<SandboxOutput<J>> {
  const timeoutMs = opts.timeoutMs ?? 20_000;
  const memoryMb = opts.memoryMb ?? 512;
  opts.signal?.throwIfAborted();
  if (inProcessReason) return runInProcess(job, input, timeoutMs) as Promise<SandboxOutput<J>>;
  const { cmd, args } = command(memoryMb);
  let child: Deno.ChildProcess;
  try {
    child = new Deno.Command(cmd, {
      args,
      stdin: "piped",
      stdout: "piped",
      stderr: "piped",
      env: {},
      clearEnv: true,
    }).spawn();
  } catch (e) {
    inProcessReason = (e as Error).message;
    console.warn(`[sandbox] 起不来子进程，退回进程内执行：${inProcessReason}`);
    return runInProcess(job, input, timeoutMs) as Promise<SandboxOutput<J>>;
  }
  stats.spawned += 1;
  let killedFor: SandboxErrorKind | null = null;
  const kill = (why: SandboxErrorKind) => {
    if (killedFor) return;
    killedFor = why;
    try {
      child.kill("SIGKILL");
    } catch {
      // 已退出
    }
  };
  const timer = setTimeout(() => kill("timeout"), timeoutMs);
  const watch = setInterval(async () => {
    const kb = await rssKb(child.pid);
    if (kb !== null && kb > memoryMb * 1024) kill("memory");
  }, 100);
  const onAbort = () => kill("crash");
  opts.signal?.addEventListener("abort", onAbort, { once: true });
  try {
    const w = child.stdin.getWriter();
    await w.write(new TextEncoder().encode(JSON.stringify({ job, input }))).catch(() => undefined);
    await w.close().catch(() => undefined);
    const [status, stdout, stderr] = await Promise.all([
      child.status,
      new Response(child.stdout).text(),
      new Response(child.stderr).text(),
    ]);
    if (killedFor === "timeout") {
      stats.timeouts += 1;
      throw new SandboxError("timeout", `沙箱任务 ${job} 超过 ${timeoutMs} ms 未完成，已强制结束`);
    }
    if (killedFor === "memory" || /out of memory|heap limit/i.test(stderr)) {
      stats.memoryKills += 1;
      throw new SandboxError("memory", `沙箱任务 ${job} 内存超过 ${memoryMb} MB，已强制结束`);
    }
    opts.signal?.throwIfAborted();
    const line = stdout.trim().split("\n").pop() ?? "";
    let msg: { ok: boolean; result?: unknown; error?: string };
    try {
      msg = JSON.parse(line);
    } catch {
      stats.crashes += 1;
      throw new SandboxError("crash", `沙箱任务 ${job} 异常退出（code ${status.code}）：${stderr.trim().slice(-300)}`);
    }
    if (!msg.ok) throw new SandboxError("job", msg.error ?? "沙箱任务失败");
    return msg.result as SandboxOutput<J>;
  } finally {
    clearTimeout(timer);
    clearInterval(watch);
    opts.signal?.removeEventListener("abort", onAbort);
  }
}

async function runInProcess<J extends SandboxJobName>(
  job: J,
  input: SandboxInput<J>,
  timeoutMs: number,
): Promise<unknown> {
  await prepareJobs();
  const fn = SANDBOX_JOBS[job] as (i: SandboxInput<J>) => unknown;
  let timer: ReturnType<typeof setTimeout> | undefined;
  try {
    return await Promise.race([
      Promise.resolve().then(() => fn(input)),
      new Promise<never>((_, reject) => {
        timer = setTimeout(() => reject(new SandboxError("timeout", `沙箱任务 ${job} 超时（进程内）`)), timeoutMs);
      }),
    ]);
  } catch (e) {
    if (e instanceof SandboxError) throw e;
    throw new SandboxError("job", `${(e as Error).name}: ${(e as Error).message}`);
  } finally {
    clearTimeout(timer);
  }
}