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/*
 * Copyright (C) 2016 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package okhttp3.internal.http

import okhttp3.Interceptor
import okhttp3.OkHttpClient
import okhttp3.Request
import okhttp3.Response
import okhttp3.Route
import okhttp3.internal.closeQuietly
import okhttp3.internal.connection.RouteException
import okhttp3.internal.connection.Transmitter
import okhttp3.internal.http.StatusLine.Companion.HTTP_PERM_REDIRECT
import okhttp3.internal.http.StatusLine.Companion.HTTP_TEMP_REDIRECT
import okhttp3.internal.http2.ConnectionShutdownException
import okhttp3.internal.canReuseConnectionFor
import java.io.FileNotFoundException
import java.io.IOException
import java.io.InterruptedIOException
import java.net.HttpURLConnection.HTTP_CLIENT_TIMEOUT
import java.net.HttpURLConnection.HTTP_MOVED_PERM
import java.net.HttpURLConnection.HTTP_MOVED_TEMP
import java.net.HttpURLConnection.HTTP_MULT_CHOICE
import java.net.HttpURLConnection.HTTP_PROXY_AUTH
import java.net.HttpURLConnection.HTTP_SEE_OTHER
import java.net.HttpURLConnection.HTTP_UNAUTHORIZED
import java.net.HttpURLConnection.HTTP_UNAVAILABLE
import java.net.ProtocolException
import java.net.Proxy
import java.net.SocketTimeoutException
import java.security.cert.CertificateException
import javax.net.ssl.SSLHandshakeException
import javax.net.ssl.SSLPeerUnverifiedException

/**
 * This interceptor recovers from failures and follows redirects as necessary. It may throw an
 * [IOException] if the call was canceled.
 */
class RetryAndFollowUpInterceptor(private val client: OkHttpClient) : Interceptor {

  @Throws(IOException::class)
  override fun intercept(chain: Interceptor.Chain): Response {
    var request = chain.request()
    val realChain = chain as RealInterceptorChain
    val transmitter = realChain.transmitter()
    var followUpCount = 0
    var priorResponse: Response? = null
    while (true) {
      transmitter.prepareToConnect(request)

      if (transmitter.isCanceled) {
        throw IOException("Canceled")
      }

      var response: Response
      var success = false
      try {
        response = realChain.proceed(request, transmitter, null)
        success = true
      } catch (e: RouteException) {
        // The attempt to connect via a route failed. The request will not have been sent.
        if (!recover(e.lastConnectException, transmitter, false, request)) {
          throw e.firstConnectException
        }
        continue
      } catch (e: IOException) {
        // An attempt to communicate with a server failed. The request may have been sent.
        val requestSendStarted = e !is ConnectionShutdownException
        if (!recover(e, transmitter, requestSendStarted, request)) throw e
        continue
      } finally {
        // The network call threw an exception. Release any resources.
        if (!success) {
          transmitter.exchangeDoneDueToException()
        }
      }

      // Attach the prior response if it exists. Such responses never have a body.
      if (priorResponse != null) {
        response = response.newBuilder()
            .priorResponse(priorResponse.newBuilder()
                .body(null)
                .build())
            .build()
      }

      val exchange = response.exchange
      val route = exchange?.connection()?.route()
      val followUp = followUpRequest(response, route)

      if (followUp == null) {
        if (exchange != null && exchange.isDuplex) {
          transmitter.timeoutEarlyExit()
        }
        return response
      }

      val followUpBody = followUp.body
      if (followUpBody != null && followUpBody.isOneShot()) {
        return response
      }

      response.body?.closeQuietly()
      if (transmitter.hasExchange()) {
        exchange?.detachWithViolence()
      }

      if (++followUpCount > MAX_FOLLOW_UPS) {
        throw ProtocolException("Too many follow-up requests: $followUpCount")
      }

      request = followUp
      priorResponse = response
    }
  }

  /**
   * Report and attempt to recover from a failure to communicate with a server. Returns true if
   * `e` is recoverable, or false if the failure is permanent. Requests with a body can only
   * be recovered if the body is buffered or if the failure occurred before the request has been
   * sent.
   */
  private fun recover(
    e: IOException,
    transmitter: Transmitter,
    requestSendStarted: Boolean,
    userRequest: Request
  ): Boolean {
    // The application layer has forbidden retries.
    if (!client.retryOnConnectionFailure) return false

    // We can't send the request body again.
    if (requestSendStarted && requestIsOneShot(e, userRequest)) return false

    // This exception is fatal.
    if (!isRecoverable(e, requestSendStarted)) return false

    // No more routes to attempt.
    if (!transmitter.canRetry()) return false
    // For failure recovery, use the same route selector with a new connection.
    return true
  }

  private fun requestIsOneShot(e: IOException, userRequest: Request): Boolean {
    val requestBody = userRequest.body
    return (requestBody != null && requestBody.isOneShot()) ||
        e is FileNotFoundException
  }

  private fun isRecoverable(e: IOException, requestSendStarted: Boolean): Boolean {
    // If there was a protocol problem, don't recover.
    if (e is ProtocolException) {
      return false
    }

    // If there was an interruption don't recover, but if there was a timeout connecting to a route
    // we should try the next route (if there is one).
    if (e is InterruptedIOException) {
      return e is SocketTimeoutException && !requestSendStarted
    }

    // Look for known client-side or negotiation errors that are unlikely to be fixed by trying
    // again with a different route.
    if (e is SSLHandshakeException) {
      // If the problem was a CertificateException from the X509TrustManager,
      // do not retry.
      if (e.cause is CertificateException) {
        return false
      }
    }
    if (e is SSLPeerUnverifiedException) {
      // e.g. a certificate pinning error.
      return false
    }
    // An example of one we might want to retry with a different route is a problem connecting to a
    // proxy and would manifest as a standard IOException. Unless it is one we know we should not
    // retry, we return true and try a new route.
    return true
  }

  /**
   * Figures out the HTTP request to make in response to receiving [userResponse]. This will
   * either add authentication headers, follow redirects or handle a client request timeout. If a
   * follow-up is either unnecessary or not applicable, this returns null.
   */
  @Throws(IOException::class)
  private fun followUpRequest(userResponse: Response, route: Route?): Request? {
    val responseCode = userResponse.code

    val method = userResponse.request.method
    when (responseCode) {
      HTTP_PROXY_AUTH -> {
        val selectedProxy = route!!.proxy
        if (selectedProxy.type() != Proxy.Type.HTTP) {
          throw ProtocolException("Received HTTP_PROXY_AUTH (407) code while not using proxy")
        }
        return client.proxyAuthenticator.authenticate(route, userResponse)
      }

      HTTP_UNAUTHORIZED -> return client.authenticator.authenticate(route, userResponse)

      HTTP_PERM_REDIRECT, HTTP_TEMP_REDIRECT -> {
        // "If the 307 or 308 status code is received in response to a request other than GET
        // or HEAD, the user agent MUST NOT automatically redirect the request"
        if (method != "GET" && method != "HEAD") {
          return null
        }
        return buildRedirectRequest(userResponse, method)
      }

      HTTP_MULT_CHOICE, HTTP_MOVED_PERM, HTTP_MOVED_TEMP, HTTP_SEE_OTHER -> {
        return buildRedirectRequest(userResponse, method)
      }

      HTTP_CLIENT_TIMEOUT -> {
        // 408's are rare in practice, but some servers like HAProxy use this response code. The
        // spec says that we may repeat the request without modifications. Modern browsers also
        // repeat the request (even non-idempotent ones.)
        if (!client.retryOnConnectionFailure) {
          // The application layer has directed us not to retry the request.
          return null
        }

        val requestBody = userResponse.request.body
        if (requestBody != null && requestBody.isOneShot()) {
          return null
        }
        val priorResponse = userResponse.priorResponse
        if (priorResponse != null && priorResponse.code == HTTP_CLIENT_TIMEOUT) {
          // We attempted to retry and got another timeout. Give up.
          return null
        }

        if (retryAfter(userResponse, 0) > 0) {
          return null
        }

        return userResponse.request
      }

      HTTP_UNAVAILABLE -> {
        val priorResponse = userResponse.priorResponse
        if (priorResponse != null && priorResponse.code == HTTP_UNAVAILABLE) {
          // We attempted to retry and got another timeout. Give up.
          return null
        }

        if (retryAfter(userResponse, Integer.MAX_VALUE) == 0) {
          // specifically received an instruction to retry without delay
          return userResponse.request
        }

        return null
      }
      else -> return null
    }
  }

  private fun buildRedirectRequest(userResponse: Response, method: String): Request? {
    // Does the client allow redirects?
    if (!client.followRedirects) return null

    val location = userResponse.header("Location") ?: return null
    // Don't follow redirects to unsupported protocols.
    val url = userResponse.request.url.resolve(location) ?: return null

    // If configured, don't follow redirects between SSL and non-SSL.
    val sameScheme = url.scheme == userResponse.request.url.scheme
    if (!sameScheme && !client.followSslRedirects) return null

    // Most redirects don't include a request body.
    val requestBuilder = userResponse.request.newBuilder()
    if (HttpMethod.permitsRequestBody(method)) {
      val maintainBody = HttpMethod.redirectsWithBody(method)
      if (HttpMethod.redirectsToGet(method)) {
        requestBuilder.method("GET", null)
      } else {
        val requestBody = if (maintainBody) userResponse.request.body else null
        requestBuilder.method(method, requestBody)
      }
      if (!maintainBody) {
        requestBuilder.removeHeader("Transfer-Encoding")
        requestBuilder.removeHeader("Content-Length")
        requestBuilder.removeHeader("Content-Type")
      }
    }

    // When redirecting across hosts, drop all authentication headers. This
    // is potentially annoying to the application layer since they have no
    // way to retain them.
    if (!userResponse.request.url.canReuseConnectionFor(url)) {
      requestBuilder.removeHeader("Authorization")
    }

    return requestBuilder.url(url).build()
  }

  private fun retryAfter(userResponse: Response, defaultDelay: Int): Int {
    val header = userResponse.header("Retry-After") ?: return defaultDelay

    // https://tools.ietf.org/html/rfc7231#section-7.1.3
    // currently ignores a HTTP-date, and assumes any non int 0 is a delay
    if (header.matches("\\d+".toRegex())) {
      return Integer.valueOf(header)
    }
    return Integer.MAX_VALUE
  }

  companion object {
    /**
     * How many redirects and auth challenges should we attempt? Chrome follows 21 redirects; Firefox,
     * curl, and wget follow 20; Safari follows 16; and HTTP/1.0 recommends 5.
     */
    private const val MAX_FOLLOW_UPS = 20
  }
}




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