Releases only provided number of tokens per provided timeunit, otherwise forces the caller to wait until the next set of tokens available

RateLimiter.kt

class RateLimiter(val time: Long, val timeUnit: TimeUnit, val noOfTokensPerSlot: Int)
{
	private val timeInMillis = timeUnit.toMillis(time)

	private var tokensReleasedTime = (System.currentTimeMillis() / 1000) * 1000
	private var availableTokens = noOfTokensPerSlot

	init
	{
		require(time > 0, { "time[$time] should be positive" })
		require(noOfTokensPerSlot > 0, { "noOfTokens[$noOfTokensPerSlot] should be positive" })
	}

	fun acquireSome(noOfTokensRequired: Int = 1): Int = acquire(noOfTokensRequired, false)

	fun acquireAll(noOfTokensRequired: Int = 1) = acquire(noOfTokensRequired, true)

	private fun acquire(noOfTokens: Int, acquireAll: Boolean): Int
	{
		require(noOfTokens in 0..noOfTokensPerSlot)

		val nextTokensReleaseTime = tokensReleasedTime + timeInMillis;
		val currentTime = System.currentTimeMillis()

		if (nextTokensReleaseTime <= currentTime)
		{
			tokensReleasedTime += ((currentTime - tokensReleasedTime) / timeInMillis) * timeInMillis
			availableTokens = noOfTokensPerSlot - noOfTokens
		} else if (noOfTokens <= availableTokens)
		{
			availableTokens -= noOfTokens
		} else if (acquireAll || availableTokens == 0)
		{
			Thread.sleep(nextTokensReleaseTime - currentTime);
			tokensReleasedTime = nextTokensReleaseTime
			availableTokens = noOfTokensPerSlot - noOfTokens
		} else
		{
			val fewAvailableTokens = availableTokens
			availableTokens = 0
			return fewAvailableTokens
		}
		return noOfTokens
	}
}