/**
 * Array or element of an array
 */
export type MaybeArray<T> = T | T[];

/**
 * convert to single value object
 */
export function objectOfMaybeArray<T = any>(
	o: Record<string, MaybeArray<T>>,
	keys: string[] | null = null,
	picker = firstOfMaybeArray,
): Record<string, T> {
	if (keys === null) {
		return Object.fromEntries(Object.entries(o).map(([k, v]) => [k, picker(v)]));
	}
	return Object.fromEntries(keys.map((v) => [v, picker(v)])) as any;
}

export function firstOfMaybeArray<T>(v: MaybeArray<T>): T {
	if (Array.isArray(v)) {
		return v[0];
	}
	return v;
}

export function lastOfMaybeArray<T>(v: MaybeArray<T>): T {
	if (Array.isArray(v)) {
		return v[v.length - 1];
	}
	return v;
}

export function arrayOfMaybeArray<T>(v: MaybeArray<T> | null | undefined): T[] {
	if (Array.isArray(v)) {
		return v;
	}
	if (v === null || v === undefined) {
		return [];
	}
	return [v];
}