import { PassThrough } from "stream";

interface StreamEntry {
  stream: PassThrough;
  createdAt: number;
}

class StreamRegistry {
  private readonly streams = new Map<string, StreamEntry>();
  private readonly TTL_MS = 5 * 60 * 1000;

  register(jobId: string): PassThrough {
    const existing = this.streams.get(jobId);
    if (existing) {
      existing.stream.destroy();
    }
    const stream = new PassThrough();
    this.streams.set(jobId, { stream, createdAt: Date.now() });

    stream.on("close", () => {
      this.streams.delete(jobId);
    });

    this.evictExpired();
    return stream;
  }

  get(jobId: string): PassThrough | null {
    return this.streams.get(jobId)?.stream ?? null;
  }

  write(jobId: string, chunk: string): void {
    this.streams.get(jobId)?.stream.write(chunk);
  }

  end(jobId: string): void {
    const entry = this.streams.get(jobId);
    if (entry) {
      entry.stream.end();
      this.streams.delete(jobId);
    }
  }

  private evictExpired(): void {
    const now = Date.now();
    for (const [id, entry] of this.streams.entries()) {
      if (now - entry.createdAt > this.TTL_MS) {
        entry.stream.destroy();
        this.streams.delete(id);
      }
    }
  }
}

export const streamRegistry = new StreamRegistry();