/**
 * Bounded in-memory ring buffer for Jetstream cursor replay.
 */
import type { JetstreamMessage } from "~/lib/jetstream-envelope";

export class JetstreamRingBuffer {
  private frames: JetstreamMessage[] = [];

  constructor(private readonly maxSize: number) {}

  append(frame: JetstreamMessage): void {
    this.frames.push(frame);
    if (this.frames.length > this.maxSize) {
      this.frames.shift();
    }
  }

  /** Frames with time_us strictly greater than cursor, in insertion order. */
  replayAfter(cursor: number | null): JetstreamMessage[] {
    if (cursor == null) return [];
    return this.frames.filter((frame) => frame.time_us > cursor);
  }

  size(): number {
    return this.frames.length;
  }
}