import { ChildProcessWithoutNullStreams } from 'child_process';

export class TranscodeThrottler {
  private timer?: NodeJS.Timeout;
  private encoderPosition = 0;
  private playheadPosition = 0;
  private userPaused = false;
  private ffmpegPaused = false;

  constructor(private readonly process: ChildProcessWithoutNullStreams) {}

  start(): void {
    this.timer = setInterval(() => this.tick(), 1000);
    this.timer.unref();
  }

  stop(): void {
    if (this.timer) {
      clearInterval(this.timer);
      this.timer = undefined;
    }
  }

  updateProgress(stderrLine: string): void {
    const match = stderrLine.match(/time=(\d{2}):(\d{2}):(\d{2}(?:\.\d+)?)/);
    if (!match) return;
    const hours = Number(match[1]);
    const minutes = Number(match[2]);
    const seconds = Number(match[3]);
    this.encoderPosition = hours * 3600 + minutes * 60 + seconds;
  }

  updateClient(position: number, isPaused: boolean): void {
    this.playheadPosition = Math.max(0, position);
    this.userPaused = isPaused;
  }

  private tick(): void {
    const gap = this.encoderPosition - this.playheadPosition;
    if (!this.ffmpegPaused && !this.userPaused && gap > 60) {
      this.process.stdin.write('p\n');
      this.ffmpegPaused = true;
      return;
    }

    if (this.ffmpegPaused && (!this.userPaused || gap < 30)) {
      this.process.stdin.write('u\n');
      this.ffmpegPaused = false;
    }
  }
}