import * as plugins from './classes.plugins.js';

export class BackpressuredArray<T> {
  public data: T[];
  private highWaterMark: number;
  public hasSpace = new plugins.smartrx.rxjs.Subject<'hasSpace'>();
  private itemsAvailable = new plugins.smartrx.rxjs.Subject<'itemsAvailable'>();

  constructor(highWaterMark: number = 16) {
    this.data = [];
    this.highWaterMark = highWaterMark;
  }

  push(item: T): boolean {
    this.data.push(item);
    this.itemsAvailable.next('itemsAvailable');
    
    const spaceAvailable = this.checkSpaceAvailable();
    if (spaceAvailable) {
      this.hasSpace.next('hasSpace');
    }
    return spaceAvailable;
  }

  shift(): T | undefined {
    const item = this.data.shift();
    if (this.checkSpaceAvailable()) {
      this.hasSpace.next('hasSpace');
    }
    return item;
  }

  checkSpaceAvailable(): boolean {
    return this.data.length < this.highWaterMark;
  }

  waitForSpace(): Promise<void> {
    return new Promise<void>((resolve) => {
      if (this.checkSpaceAvailable()) {
        resolve();
      } else {
        const subscription = this.hasSpace.subscribe(() => {
          subscription.unsubscribe();
          resolve();
        });
      }
    });
  }

  waitForItems(): Promise<void> {
    return new Promise<void>((resolve) => {
      if (this.data.length > 0) {
        resolve();
      } else {
        const subscription = this.itemsAvailable.subscribe(() => {
          subscription.unsubscribe();
          resolve();
        });
      }
    });
  }
}