export class ConnectionStats {
  /** The duration of that stats window in milliseconds. */
  windowDuration: number;

  /** The window of most recently sent packets. */
  window: Array<{ timestamp: number; bytes: number }> = [];

  constructor(windowDuration: number = 5 * 1000) {
    this.windowDuration = windowDuration;
  }

  updateWindow() {
    const windowStart = performance.now() - this.windowDuration;
    while (this.window.length > 0) {
      if (this.window[0].timestamp < windowStart) this.window.shift();
      else break;
    }
  }

  onMessage(byteLength: number) {
    this.window.push({
      timestamp: performance.now(),
      bytes: byteLength,
    });
    this.updateWindow();
  }

  getPacketsPerSecond(): number {
    this.updateWindow();
    return (1000 * this.window.length) / this.windowDuration;
  }

  getAveragePacketSize() {
    this.updateWindow();
    const bytes = this.window.reduce((a, b) => a + b.bytes, 0);
    return bytes / this.window.length;
  }

  getBytesPerSecond() {
    this.updateWindow();
    const bytes = this.window.reduce((a, b) => a + b.bytes, 0);
    return (1000 * bytes) / this.windowDuration;
  }

  formatStats() {
    return `${this.getPacketsPerSecond().toFixed(
      2
    )} msgs/sec, ${this.getAveragePacketSize().toFixed(
      2
    )} bytes/msg, ${this.getBytesPerSecond()} bytes/sec`;
  }
}