import type { Message } from './message.gen';
import type { RawMessage } from './raw.gen';
import { MType } from './raw.gen';

interface RawMessageReaderI {
  readMessage(): RawMessage | null;
}

export default class MStreamReader {
  constructor(
    private readonly r: RawMessageReaderI,
    private startTs: number = 0,
  ) {}

  private t: number = 0;

  private idx: number = 0;

  currentTab = 'back-compatability';

  readNext(): (Message & { _index: number; tabId: string }) | null {
    const msg = this.r.readMessage();
    if (msg === null) {
      return null;
    }
    if (msg.tp === MType.Timestamp) {
      this.startTs = this.startTs || msg.timestamp;
      const newT = msg.timestamp - this.startTs;
      if (newT > this.t) {
        this.t = newT;
      }
      return this.readNext();
    }
    if (msg.tp === MType.TabData) {
      this.currentTab = msg.tabId;
      return this.readNext();
    }

    return Object.assign(msg, {
      time: this.t,
      _index: this.idx++,
      tabId: this.currentTab,
    });
  }
}