import type { ChildProcess } from "node:child_process";

/**
 * Ensures that all data from a child process's stdout and stderr pipes
 * has been fully drained before resolving. This prevents a common race
 * condition where the process exits but the OS hasn't finished flushing
 * the last few buffers to the parent.
 *
 * NOTE: This is forward-looking scaffolding for when the codebase spawns
 * async child processes. Currently all child process use is synchronous
 * (execFileSync), which has no stdio pipes to drain.
 */
export async function waitForProcessDrain(child: ChildProcess): Promise<void> {
  const pipes: Promise<void>[] = [];

  if (child.stdout) {
    pipes.push(new Promise<void>((resolve) => {
      child.stdout?.on("end", resolve);
      // Ensure we don't hang if stdout was already closed
      if (child.stdout?.destroyed) resolve();
    }));
  }

  if (child.stderr) {
    pipes.push(new Promise<void>((resolve) => {
      child.stderr?.on("end", resolve);
      // Ensure we don't hang if stderr was already closed
      if (child.stderr?.destroyed) resolve();
    }));
  }

  await Promise.all(pipes);
}