private fun computeCandidate(): CacheStrategy {
      // No cached response.
      if (cacheResponse == null) {
        return CacheStrategy(request, null)
      }

      // Drop the cached response if it's missing a required handshake.
      if (request.isHttps && cacheResponse.handshake == null) {
        return CacheStrategy(request, null)
      }

  )
  fun directory(): File = cache.directory.toFile()

  @Synchronized internal fun trackResponse(cacheStrategy: CacheStrategy) {
    requestCount++

    if (cacheStrategy.networkRequest != null) {
      // If this is a conditional request, we'll increment hitCount if/when it hits.
      networkCount++
    } else if (cacheStrategy.cacheResponse != null) {
      // This response uses the cache and not the network. That's a cache hit.

    val call = chain.call()
    val cacheCandidate = cache?.get(chain.request().requestForCache())

    val now = System.currentTimeMillis()

    val strategy = CacheStrategy.Factory(now, chain.request(), cacheCandidate).compute()
    val networkRequest = strategy.networkRequest
    val cacheResponse = strategy.cacheResponse

    cache?.trackResponse(strategy)