import { MonoTypeOperatorFunction, defer, iif, retry, tap, throwError, timer } from 'rxjs';

export const retryBackoff =
    <T>(): MonoTypeOperatorFunction<T> =>
    (source) =>
        defer(() => {
            const attempts = 4;
            const interval = 1000;

            let index = 0;

            return source.pipe(
                retry({
                    delay: (error) => {
                        index += 1;

                        return iif(
                            () => index < attempts,
                            timer(interval * index ** 2),
                            throwError(() => error) // tslint:disable-line:rxjs-throw-error
                        );
                    }
                }),
                tap(() => (index = 0))
            );
        });