import { mapApplyMaxSize } from "./map-apply-max-size.js"

/**
 * A memoization wrapper with ttl expiration for cache hits.
 *
 * @param function
 * the function to be memoized
 *
 * @param ttl
 * time to live for the cache in milliseconds
 *
 * @returns
 * last response from a function if called again with same props
 * before ttl interval has passed.
 *
 * If you only need basic debounce, see @slimio/util/debounce
 */
export const memoize: Memoize = <F extends Fnc>(
	/** the function to be memoized */
	fn: F,
	/** time to live for the cache in milliseconds */
	ttl = 1000,
) => {
	const throttled = (...props: any) => {
		const cacheKey = JSON.stringify({
			signature: `${fn.name}::${fn.toString().slice(0, 10)}`,
			props,
		})
		let { expires = 0, returnValue } = memoize.cache.get(cacheKey) || {
			expires: 0,
			returnValue: null,
		}
		const now = Date.now()
		if (now > expires) {
			expires = now + ttl
			returnValue = fn(...props)
			memoize.cache.set(cacheKey, { expires, returnValue })
		}
		return returnValue
	}
	return throttled as F
}
memoize.cache = new Map<string, { expires: number; returnValue: any }>()
mapApplyMaxSize(memoize.cache, 200)

type Fnc = (...args: any) => any
type Memoize = {
	// eslint-disable-next-line @typescript-eslint/ban-types
	<F extends Fnc>(fn: F, ttl: number): F
	cache: Map<string, { returnValue: any; expires: number }>
}