import { execa } from "execa";
import {
  classifyFfmpegProbe,
  type StreamVerdict,
} from "./ffmpegStreamClassify";

export type ProbeAudioStreamOptions = {
  ffmpegBin: string;
  file: string;
  signal: AbortSignal;
  onLog?: (s: string) => void;
  // Target audio codec for the probe transcode. We mirror the channel's
  // output codec so the probe exercises the same encode path the final
  // transcode will use. Defaults to libmp3lame.
  codecArg?: string;
};

export type ProbeAudioStreamResult = {
  verdict: StreamVerdict;
  stderr: string;
  exitCode: number | null;
};

// Probe by performing a real audio transcode to /dev/null. The exit code is
// the authoritative signal:
//   - 0     → clean (or partial-but-decodable; either is fine for our flow)
//   - != 0  → malformed (a real codec error tripped ffmpeg)
// ffmpeg treats a truncated container as a recoverable warning ("partial
// file" stderr line, exit 0). Only true mid-stream corruption — e.g. AAC's
// "Sample rate index in program config element does not match" — produces a
// non-zero exit. -xerror with -f null underreports because the null muxer
// swallows decoder errors during write.
export async function probeAudioStream(
  opts: ProbeAudioStreamOptions,
): Promise<ProbeAudioStreamResult> {
  const codecArg = opts.codecArg ?? "libmp3lame";
  const args = [
    "-y",
    "-v",
    "error",
    "-nostdin",
    "-i",
    opts.file,
    "-vn",
    "-c:a",
    codecArg,
    "-f",
    "mp3",
    "/dev/null",
  ];
  opts.onLog?.(`$ ${opts.ffmpegBin} ${args.join(" ")}\n`);
  const child = execa(opts.ffmpegBin, args, {
    cancelSignal: opts.signal,
    all: false,
    buffer: false,
    reject: false,
  });
  let stderr = "";
  child.stderr?.on("data", (c: Buffer) => {
    const chunk = c.toString("utf8");
    stderr += chunk;
    opts.onLog?.(chunk);
  });
  child.stdout?.on("data", () => {});
  const result = await child;
  const exitCode = result.exitCode ?? null;
  return {
    verdict: classifyFfmpegProbe(exitCode, stderr),
    stderr,
    exitCode,
  };
}