export type RNG = (max?: number, min?: number) => number
export function random(max: number, min: number = 0, rng?: RNG): number {
    if (rng) return rng(max, min)
    return Math.floor(Math.random() * (max - min + 1)) + min
}
export function pick<T>(items: T[], rng?: RNG) {
    if (items.length === 0) return null
    return items[random(items.length - 1, 0, rng)] ?? null
}
export type WeightItem<T> = [T, number]
export function pickWeight<T>(items: WeightItem<T>[], rng?: RNG) {
    if (items.length === 0) return null
    const totalWeight = items.reduce((sum, [, weight]) => sum + weight, 0)
    let mark = random(totalWeight - 1, 0, rng)
    for (const [item, weight] of items) {
        if (mark < weight) return item
        mark -= weight
    }
    return null
}

export function sum(arr: number[]) {
    return arr.reduce((sum, v) => sum + v, 0)
}