import { Injectable } from '@angular/core';
import { fromEvent, merge, Observable, Subject } from 'rxjs';
import { filter, map, startWith } from 'rxjs/operators';

export interface LocalStorageObject {
	name: string;
	value: string | null;
}

const deserializeValue = <T>(value: string): T => {
	try {
		return JSON.parse(value);
	} catch {
		return value as unknown as T;
	}
};

@Injectable({
	providedIn: 'root',
})
export class LocalStorageService {
	private _storage = window.localStorage;

	private _storageUpdateNotifier$ = new Subject<LocalStorageObject | null>();

	storageUpdates$ = this._storageUpdateNotifier$.asObservable();

	initLocalStorage(storageObjs: LocalStorageObject[]): void {
		if (this._isLocalStorageEnabled()) {
			storageObjs.forEach(({ name, value }) => {
				this._storage.setItem(name, value);
			});
		}
	}

	setItem(key: string, value: string): void {
		this._storage.setItem(key, value);
		this._storageUpdateNotifier$.next({ name: key, value });
	}

	getItem(key: string): any {
		const retrieved = this._storage.getItem(key);
		try {
			return deserializeValue(retrieved);
		} catch {
			return retrieved;
		}
	}

	removeItem(key: string): void {
		this._storage.removeItem(key);
		this._storageUpdateNotifier$.next({ name: key, value: null });
	}

	clear(): void {
		this._storage.clear();
		this._storageUpdateNotifier$.next(null);
	}

	getUpdatesForKey<T>(key: string): Observable<T> {
		return merge(
			fromEvent(window, 'storage').pipe(
				filter((event: StorageEvent) => event.key === key),
				map(data => deserializeValue(data.newValue))
			),
			this.storageUpdates$.pipe(
				filter(update => update.name === key),
				map(update => deserializeValue(update.value))
			)
		).pipe(startWith(this.getItem(key) || false));
	}

	private _isLocalStorageEnabled(): boolean {
		try {
			const key = `__storage__test`;
			this._storage.setItem(key, null);
			this._storage.removeItem(key);
			return true;
		} catch (e) {
			return false;
		}
	}
}