package net.sergecyh.diwan.tools

import kotlin.time.Clock
import kotlin.time.Duration
import kotlin.time.Instant

/**
 * Experimental.
 *
 * limit invocations rate of [invoke] to once per [minimalInterval] or less frequent.
 * Note that it is not a debouncing, it just ignores too frequent calls!
 */
@Suppress("unused")
class RateLimiter(val minimalInterval: Duration) {
    var lastExecutedAt = Instant.DISTANT_PAST
        private set

    /**
     * invoke [f] if the last invocation was earlier than now minus [minimalInterval], otherwise
     * do nothing.
     * @return the value returned by [f] if it was actually invoked this time, null otherwise
     */
    suspend operator fun <T> invoke(f: suspend () -> T): T? =
        if (Clock.System.now() - lastExecutedAt > minimalInterval) {
            f().also { lastExecutedAt = Clock.System.now() }
        } else null
}