import { spawn } from "node:child_process";

const FFMPEG = process.env.FFMPEG_PATH ?? "ffmpeg";
const FFPROBE = process.env.FFPROBE_PATH ?? "ffprobe";

/** Run ffmpeg with the given args; rejects with the tail of stderr on non-zero exit. */
export function runFfmpeg(args: string[]): Promise<void> {
  return new Promise((resolve, reject) => {
    const proc = spawn(FFMPEG, args, { stdio: ["ignore", "ignore", "pipe"] });
    let stderr = "";
    proc.stderr.on("data", (d) => {
      stderr += d.toString();
    });
    proc.on("error", (err) =>
      reject(new Error(`Failed to spawn ffmpeg (${FFMPEG}): ${err.message}`))
    );
    proc.on("close", (code) =>
      code === 0 ? resolve() : reject(new Error(`ffmpeg exited ${code}: ${stderr.slice(-600)}`))
    );
  });
}

/** Probe an audio file's duration in whole seconds, or null if ffprobe is unavailable. */
export function ffprobeDuration(file: string): Promise<number | null> {
  return new Promise((resolve) => {
    const proc = spawn(FFPROBE, [
      "-v",
      "error",
      "-show_entries",
      "format=duration",
      "-of",
      "default=noprint_wrappers=1:nokey=1",
      file,
    ]);
    let out = "";
    proc.stdout.on("data", (d) => {
      out += d.toString();
    });
    proc.on("error", () => resolve(null));
    proc.on("close", () => {
      const n = parseFloat(out.trim());
      resolve(Number.isFinite(n) ? Math.round(n) : null);
    });
  });
}