export type Rng = () => number;

/** Small deterministic generator, so a daily challenge is the same all day. */
export function seeded(seed: number | string): Rng {
	let h = typeof seed === 'number' ? seed >>> 0 : 2166136261;
	if (typeof seed === 'string') {
		for (let i = 0; i < seed.length; i++) h = Math.imul(h ^ seed.charCodeAt(i), 16777619);
	}
	return () => {
		h = (h + 0x6d2b79f5) >>> 0;
		let t = h;
		t = Math.imul(t ^ (t >>> 15), t | 1);
		t ^= t + Math.imul(t ^ (t >>> 7), t | 61);
		return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
	};
}

export const int = (rng: Rng, min: number, max: number) =>
	min + Math.floor(rng() * (max - min + 1));

export const pick = <T>(rng: Rng, list: readonly T[]): T => list[Math.floor(rng() * list.length)];

export function shuffle<T>(rng: Rng, list: readonly T[]): T[] {
	const copy = [...list];
	for (let i = copy.length - 1; i > 0; i--) {
		const j = Math.floor(rng() * (i + 1));
		[copy[i], copy[j]] = [copy[j], copy[i]];
	}
	return copy;
}

/** Up to `count` distinct values from `list` that differ from `exclude` once normalized. */
export function sample<T>(
	rng: Rng,
	list: readonly T[],
	count: number,
	key: (value: T) => string = String,
	exclude: string[] = []
): T[] {
	const seen = new Set(exclude.map((value) => value.toLowerCase()));
	const out: T[] = [];
	for (const value of shuffle(rng, list)) {
		if (out.length >= count) break;
		const k = key(value).toLowerCase();
		if (seen.has(k)) continue;
		seen.add(k);
		out.push(value);
	}
	return out;
}