ui/src/frontend/task_tracker.ts

interface PromiseInfo {
  startTimeMs: number;
  message: string;
}

export class TaskTracker {
  private promisesSeen: number;
  private promisesRejected: number;
  private promisesFulfilled: number;
  private promiseInfo: Map<Promise<unknown>, PromiseInfo>;

  constructor() {
    this.promisesSeen = 0;
    this.promisesRejected = 0;
    this.promisesFulfilled = 0;
    this.promiseInfo = new Map();
  }

  trackPromise(promise: Promise<unknown>, message: string): void {
    this.promiseInfo.set(promise, {
      startTimeMs: (new Date()).getMilliseconds(),
      message,
    });
    this.promisesSeen += 1;
    promise.then(() => {
      this.promisesFulfilled += 1;
    }).catch(() => {
      this.promisesRejected += 1;
    }).finally(() => {
      this.promiseInfo.delete(promise);
    });
  }

  hasPendingTasks(): boolean {
    return this.promisesSeen > (this.promisesFulfilled + this.promisesRejected);
  }

  progressMessage(): string|undefined {
    const {value} = this.promiseInfo.values().next();
    if (value === undefined) {
      return value;
    } else {
      const nowMs = (new Date()).getMilliseconds();
      const runtimeSeconds = Math.round((nowMs - value.startTimeMs) / 1000);
      return `${value.message} (${runtimeSeconds}s)`;
    }
  }
}

export const taskTracker = new TaskTracker();