import { Injectable } from '@angular/core';
import { BehaviorSubject } from 'rxjs';

const MIN_LOADING_TIME = 300;

@Injectable({ providedIn: 'root' })
export class LoadingService {
    private readonly _loadingEvent$ = new BehaviorSubject(false);
    readonly isLoading$ = this._loadingEvent$.asObservable();
    private _loadingStarted = 0;

    start(): void {
        setTimeout(() => {
            this._loadingEvent$.next(true);
            this._loadingStarted = new Date().getTime();
        });
    }

    stop(): void {
        const timeSinceStarted = new Date().getTime() - this._loadingStarted;
        const remainingLoadingTime = MIN_LOADING_TIME - timeSinceStarted;

        return remainingLoadingTime > 0 ? this._stopAfter(remainingLoadingTime) : this._stop();
    }

    loadWhile(func: Promise<unknown>): void {
        this.start();

        func.then(
            () => this.stop(),
            () => this.stop(),
        );
    }

    private _stop(): void {
        setTimeout(() => this._loadingEvent$.next(false));
    }

    private _stopAfter(timeout: number): void {
        setTimeout(() => this._stop(), timeout);
    }
}