// use this to more concisely define values with one or more fallbacks to use when they are null.

// If called with two args, the second one has to be non-null
// if called with three args, the third one has to be non-null
//
// in two-arg mode, if the first argument is not null, then it's returned and fallback is not used.
//                  if the first argument is null, then the second arg is returned
//
// in three-arg mode, the first value is never returned. If the first arg is not-null, then the second arg is returned (if it's not null). Otherwise the third arg is returned

export function withFallback<T1, T2 extends NonNullable<unknown>>(
	value1: T1,
	value2: T2
): NonNullable<T1> | T2;
export function withFallback<T1, T2, T3 extends NonNullable<unknown>>(
	value1: T1,
	value2: T2,
	value3?: T3
): NonNullable<T2> | T3;
export function withFallback<T1, T2, T3 extends NonNullable<unknown>>(
	value1: T1,
	value2: T2,
	value3?: T3
): NonNullable<T1> | NonNullable<T2> | T3 {
	if (value3 !== undefined) {
		// three arg mode
		if (
			value1 !== null &&
			value1 !== undefined &&
			value2 !== null &&
			value2 !== undefined
		) {
			return value2;
		} else {
			return value3;
		}
	} else {
		// two arg mode
		if (value1 !== null && value1 !== undefined) {
			return value1;
		} else if (value2 !== undefined && value2 !== null) {
			return value2;
		} else {
			throw new Error("No suitable fallback: ${arguments}");
		}
	}
}