ExpiringCache.kt

import android.os.SystemClock

/**
 * @param expireTime Cache expire time(ms).
 */
class ExpiringCache<V: Any>(private val expireTime: Long) {
    private var cache: V? = null
    private var expirationTime: Long = 0

    fun get(): V? {
        synchronized(this) {
            val value = cache
            if (value != null && elapsedRealtime() >= expirationTime) {
                remove()
                return null
            } else {
                return value
            }
        }
    }

    fun set(value: V): V? {
        synchronized(this) {
            val previousValue = cache
            cache = value
            expirationTime = elapsedRealtime() + expireTime
            return previousValue
        }
    }

    fun elapsedRealtime(): Long {
        return SystemClock.elapsedRealtime()
    }

    fun getExpiryTime(): Long {
        return expirationTime
    }

    fun removeExpiryTime() {
        expirationTime = 0
    }

    fun remove(): V? {
        synchronized(this) {
            val previousValue = cache
            cache = null
            expirationTime = 0
            return previousValue
        }
    }
}