nope/lib/observables/nopeObservable.ts

import { BehaviorSubject, CompletionObserver, ErrorObserver, NextObserver, Subscription } from 'rxjs';

export interface nopeObserver {
  active: boolean;
}

export declare type NopePartialObserver<T> = NextObserver<T> & nopeObserver | ErrorObserver<T> & nopeObserver | CompletionObserver<T> & nopeObserver;

/**
 * RsJX based Observable.
 * 
 * Contains additional Functionalities like:
 *  - property with the current value
 *  - function to publish values. (wrapper for next)
 *  - enables performing a subscription with synced call or a immediate call.
 */
export class nopeObservable<T> extends BehaviorSubject<T> {

  protected _currentValue: T;

  /**
   * Getter for the Current Value.
   */
  public get currentValue(): T {
    return this._currentValue;
  }

  /**
   * Setter for the Current value.
   */
  public set currentValue(value: T) {
    this.next(value);
  }

  /**
   * Creates a custom Observable.
   * @param initialValue 
   */
  constructor(initialValue: T) {
    super(initialValue);

    const _this = this;
    this.subscribe((data) => {
      _this._currentValue = data;
    });
  }

  /**
   * Function to Publish a Value to the stream.
   * @param value The Value.
   */
  publish(value: T) {
    this.next(value);
  }

  subscribe(observer?: NopePartialObserver<T>, cbMode?: 'sync' | 'immediate'): Subscription;
  /** @deprecated Use an observer instead of a complete callback */
  subscribe(next: null | undefined, error: null | undefined, complete: () => void, cbMode?: 'sync' | 'immediate'): Subscription;
  /** @deprecated Use an observer instead of an error callback */
  subscribe(next: null | undefined, error: (error: any) => void, complete?: () => void, cbMode?: 'sync' | 'immediate'): Subscription;
  /** @deprecated Use an observer instead of a complete callback */
  subscribe(next: (value: T) => void, error: null | undefined, complete: () => void, cbMode?: 'sync' | 'immediate'): Subscription;
  subscribe(next?: (value: T) => void, error?: (error: any) => void, complete?: () => void, cbMode?: 'sync' | 'immediate'): Subscription;

  // Underlying implementation
  subscribe(observerOrNext?, errorOrcbMode?, complete?: () => void, cbMode?: 'sync' | 'immediate'): Subscription {
    // The first argument could be an Observer or Callback (Depricated) and the callbacks for complete and error  
    let _cbMode = cbMode;
    let _error = errorOrcbMode;
    let _complete = complete;
    let _observerOrNext = observerOrNext;

    // If the first argument is an Observer => the second argument must be the cbMode
    if (typeof observerOrNext === 'object') {
      // Adapt the Callback
      _cbMode = errorOrcbMode || 'sync';
      // The error function must be undefined
      _error = undefined;
    }

    // Test the cbMode
    if (_cbMode === 'immediate') {
      switch (typeof observerOrNext) {
        case 'object':
          if ((observerOrNext as NopePartialObserver<T>).next) {
            const orgFunc = observerOrNext.next;
            observerOrNext.next = (v: T) => setImmediate(() => {
              if ((observerOrNext as NopePartialObserver<T>).active) {
                orgFunc.call(observerOrNext, v);
              }
            });
          }
          if ((observerOrNext as NopePartialObserver<T>).error) {
            const orgFunc = observerOrNext.next;
            observerOrNext.next = (v: T) => setImmediate(() => {
              if ((observerOrNext as NopePartialObserver<T>).active) {
                orgFunc.call(observerOrNext, v);
              }
            });
          } if ((observerOrNext as NopePartialObserver<T>).complete) {
            const orgFunc = observerOrNext.next;
            observerOrNext.next = (v: T) => setImmediate(() => {
              if ((observerOrNext as NopePartialObserver<T>).active) {
                orgFunc.call(observerOrNext, v);
              }
            });
          }
          break;
        case 'function':
          _observerOrNext = typeof observerOrNext === 'function' ? (_value: T) => setImmediate(observerOrNext, _value) : observerOrNext;
          break;
        default:
          break;
      }

      _error = typeof errorOrcbMode === 'function' ? (_errorValue: any) => setImmediate(errorOrcbMode, _errorValue) : undefined;
      _complete = typeof complete === 'function' ? () => setImmediate(complete) : undefined;
    }

    return super.subscribe(_observerOrNext, _error, _complete);
  }
}