/**

  * Copyright (c) 2013-2017, jcabi.com

  * All rights reserved.

  *

  * Redistribution and use in source and binary forms, with or without

  * modification, are permitted provided that the following conditions

  * are met: 1) Redistributions of source code must retain the above

  * copyright notice, this list of conditions and the following

  * disclaimer. 2) Redistributions in binary form must reproduce the above

  * copyright notice, this list of conditions and the following

  * disclaimer in the documentation and/or other materials provided

  * with the distribution. 3) Neither the name of the jcabi.com nor

  * the names of its contributors may be used to endorse or promote

  * products derived from this software without specific prior written

  * permission.

  *

  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT

  * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND

  * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL

  * THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,

  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

  * OF THE POSSIBILITY OF SUCH DAMAGE.

  */

 package com.jcabi.github.wire;

 import com.jcabi.aspects.Immutable;

 import com.jcabi.http.Request;

 import com.jcabi.http.Response;

 import com.jcabi.http.Wire;

 import com.jcabi.log.Logger;

 import java.io.IOException;

 import java.io.InputStream;

 import java.util.Collection;

 import java.util.List;

 import java.util.Map;

 import java.util.concurrent.TimeUnit;

 import lombok.EqualsAndHashCode;

 import lombok.ToString;

 /**

  * Wire that waits if number of remaining request per hour is less than

  * a given threshold.

  *

  * <p>Github sets following headers in each response:

  * {@code X-RateLimit-Limit}, {@code X-RateLimit-Remaining}, and

  * {@code X-RateLimit-Reset}. If {@code X-RateLimit-Remaining} is

  * less than a given threshold, {@code CarefulWire} will sleep until a time

  * specified in the {@code X-RateLimit-Reset} header. For further information

  * about the Github rate limiting see

  * <a href="http://developer.github.com/v3/#rate-limiting">API

  * documentation</a>.

  *

  * <p>You can use {@code CarefulWire} with a {@link com.jcabi.github.Github}

  * object:

  * <pre>

  * {@code

  * Github github = new RtGithub(

  *     new RtGithub().entry().through(CarefulWire.class, 50)

  * );

  * }

  * </pre>

  *

  * @author Alexander Sinyagin (sinyagin.alexander@gmail.com)

  * @version $Id: f0c987f2ce8f15ef9e457ba81a917c13a1c896f2 $

  */

 @Immutable

 @ToString

 @EqualsAndHashCode(of = { "origin", "threshold" })

 @SuppressWarnings("PMD.AvoidDuplicateLiterals")

 public final class CarefulWire implements Wire {

     /**

      * Original wire.

      */

     private final transient Wire origin;

     /**

      * Threshold of number of remaining requests, below which requests are

      * blocked until reset.

      */

     private final transient int threshold;

     /**

      * Public ctor.

      *

      * @param wire Original wire

      * @param thrshld Threshold of number of remaining requests, below which

      *  requests are blocked until reset

      */

     public CarefulWire(final Wire wire, final int thrshld) {

         this.origin = wire;

         this.threshold = thrshld;

     }

     @Override

     // @checkstyle ParameterNumber (8 lines)

     public Response send(

         final Request req,

         final String home,

         final String method,

         final Collection<Map.Entry<String, String>> headers,

         final InputStream content,

         final int connect, final int read

     ) throws IOException {

         final Response resp = this.origin

             .send(req, home, method, headers, content, connect, read);

         final int remaining = this.remainingHeader(resp);

         if (remaining < this.threshold) {

             final long reset = this.resetHeader(resp);

             final long now = TimeUnit.MILLISECONDS

                 .toSeconds(System.currentTimeMillis());

             if (reset > now) {

                 final long length = reset - now;

                 Logger.info(

                     this,

                     // @checkstyle LineLength (1 line)

                     "Remaining number of requests per hour is less than %d. Waiting for %d seconds.",

                     this.threshold, length

                 );

                 try {

                     TimeUnit.SECONDS.sleep(length);

                 } catch (final InterruptedException ex) {

                     Thread.currentThread().interrupt();

                     throw new IllegalStateException(ex);

                 }

             }

         }

         return resp;

     }

     /**

      * Get the header with the given name from the response.

      * If there is no such header, returns null.

      * @param resp Response to get header from

      * @param headername Name of header to get

      * @return The value of the first header with the given name, or null.

      */

     private String headerOrNull(

         final Response resp,

         final String headername) {

         final List<String> values = resp.headers().get(headername);

         String value = null;

         if (values != null && !values.isEmpty()) {

             value = values.get(0);

         }

         return value;

     }

     /**

      * Returns the value of the X-RateLimit-Remaining header.

      * If there is no such header, returns Integer.MAX_VALUE (no rate limit).

      * @param resp Response to get header from

      * @return Number of requests remaining before the rate limit will be hit

      */

     private int remainingHeader(

         final Response resp) {

         final String remainingstr = this.headerOrNull(

             resp,

             "X-RateLimit-Remaining"

         );

         int remaining = Integer.MAX_VALUE;

         if (remainingstr != null) {

             remaining = Integer.parseInt(remainingstr);

         }

         return remaining;

     }

     /**

      * Returns the value of the X-RateLimit-Reset header.

      * If there is no such header, returns 0 (reset immediately).

      * @param resp Response to get header from

      * @return Timestamp (in seconds) at which the rate limit will reset

      */

     private long resetHeader(

         final Response resp) {

         final String resetstr = this.headerOrNull(resp, "X-RateLimit-Reset");

         long reset = 0;

         if (resetstr != null) {

             reset = Long.parseLong(resetstr);

         }

         return reset;

     }

 }