import java.util.LinkedHashMap

class LRUCache<K : Any, V : Any>(
    val capacity: Int,
    val onRemove: (key: K, value: V) -> Unit = { _, _ -> }
) {
    private val map: LinkedHashMap<K, V> = LinkedHashMap(capacity+1, 1f, true)

    operator fun get(key: K): V? {
        return map[key]
    }

    operator fun set(key: K, value: V) {
        map[key] = value

        if (map.size > capacity) {
            val removedKey = map.keys.iterator().next()
            val removedValue = requireNotNull(map.remove(removedKey))
            onRemove(removedKey, removedValue)
        }
    }
}