/**
 * Copyright 2012-2020 The Feign Authors
 *
 * 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 feign;

/**
 * Zero or more {@code RequestInterceptors} may be configured for purposes such as adding headers to
 * all requests. No guarantees are give with regards to the order that interceptors are applied.
 * Once interceptors are applied, {@link Target#apply(RequestTemplate)} is called to create the
 * immutable http request sent via {@link Client#execute(Request, feign.Request.Options)}. <br>
 * <br>
 * For example: <br>
 * 
 * <pre>
 * public void apply(RequestTemplate input) {
 *   input.header(&quot;X-Auth&quot;, currentToken);
 * }
 * </pre>
 * 
 * <br>
 * <br>
 * <b>Configuration</b><br>
 * <br>
 * {@code RequestInterceptors} are configured via {@link Feign.Builder#requestInterceptors}. <br>
 * <br>
 * <b>Implementation notes</b><br>
 * <br>
 * Do not add parameters, such as {@code /path/{foo}/bar } in your implementation of
 * {@link #apply(RequestTemplate)}. <br>
 * Interceptors are applied after the template's parameters are
 * {@link RequestTemplate#resolve(java.util.Map) resolved}. This is to ensure that you can implement
 * signatures are interceptors. <br>
 * <br>
 * <br>
 * <b>Relationship to Retrofit 1.x</b><br>
 * <br>
 * This class is similar to {@code RequestInterceptor.intercept()}, except that the implementation
 * can read, remove, or otherwise mutate any part of the request template.
 */
public interface RequestInterceptor {

  /**
   * Called for every request. Add data using methods on the supplied {@link RequestTemplate}.
   */
  void apply(RequestTemplate template);
}