import fsSync from "node:fs";

/**
 * Check if a process is a zombie on Linux by reading /proc/<pid>/status.
 * Returns false on non-Linux platforms or if the proc file can't be read.
 */
function isZombieProcess(pid: number): boolean {
  if (process.platform !== "linux") {
    return false;
  }
  try {
    const status = fsSync.readFileSync(`/proc/${pid}/status`, "utf8");
    const stateMatch = status.match(/^State:\s+(\S)/m);
    return stateMatch?.[1] === "Z";
  } catch {
    return false;
  }
}

export function isPidAlive(pid: number): boolean {
  if (!Number.isFinite(pid) || pid <= 0) {
    return false;
  }
  try {
    process.kill(pid, 0);
  } catch {
    return false;
  }
  if (isZombieProcess(pid)) {
    return false;
  }
  return true;
}