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   /*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project licenses this file to you 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:
    *
    *   https://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 io.netty.handler.codec.http;
  
  import io.netty.util.AsciiString;
  
  import static io.netty.util.internal.MathUtil.findNextPositivePowerOfTwo;
  import static io.netty.util.internal.ObjectUtil.checkNonEmptyAfterTrim;
  
  /**
   * The request method of HTTP or its derived protocols, such as
   * <a href="https://en.wikipedia.org/wiki/Real_Time_Streaming_Protocol">RTSP</a> and
   * <a href="https://en.wikipedia.org/wiki/Internet_Content_Adaptation_Protocol">ICAP</a>.
   */
  public class HttpMethod implements Comparable<HttpMethod> {
      /**
       * The OPTIONS method represents a request for information about the communication options
       * available on the request/response chain identified by the Request-URI. This method allows
       * the client to determine the options and/or requirements associated with a resource, or the
       * capabilities of a server, without implying a resource action or initiating a resource
       * retrieval.
       */
      public static final HttpMethod OPTIONS = new HttpMethod("OPTIONS");
  
      /**
       * The GET method means retrieve whatever information (in the form of an entity) is identified
       * by the Request-URI.  If the Request-URI refers to a data-producing process, it is the
       * produced data which shall be returned as the entity in the response and not the source text
       * of the process, unless that text happens to be the output of the process.
       */
      public static final HttpMethod GET = new HttpMethod("GET");
  
      /**
       * The HEAD method is identical to GET except that the server MUST NOT return a message-body
       * in the response.
       */
      public static final HttpMethod HEAD = new HttpMethod("HEAD");
  
      /**
       * The POST method is used to request that the origin server accept the entity enclosed in the
       * request as a new subordinate of the resource identified by the Request-URI in the
       * Request-Line.
       */
      public static final HttpMethod POST = new HttpMethod("POST");
  
      /**
       * The PUT method requests that the enclosed entity be stored under the supplied Request-URI.
       */
      public static final HttpMethod PUT = new HttpMethod("PUT");
  
      /**
       * The PATCH method requests that a set of changes described in the
       * request entity be applied to the resource identified by the Request-URI.
       */
      public static final HttpMethod PATCH = new HttpMethod("PATCH");
  
      /**
       * The DELETE method requests that the origin server delete the resource identified by the
       * Request-URI.
       */
      public static final HttpMethod DELETE = new HttpMethod("DELETE");
  
      /**
       * The TRACE method is used to invoke a remote, application-layer loop- back of the request
       * message.
       */
      public static final HttpMethod TRACE = new HttpMethod("TRACE");
  
      /**
       * This specification reserves the method name CONNECT for use with a proxy that can dynamically
       * switch to being a tunnel
       */
      public static final HttpMethod CONNECT = new HttpMethod("CONNECT");
  
      private static final EnumNameMap<HttpMethod> methodMap;
  
      static {
          methodMap = new EnumNameMap<HttpMethod>(
                  new EnumNameMap.Node<HttpMethod>(OPTIONS.toString(), OPTIONS),
                  new EnumNameMap.Node<HttpMethod>(GET.toString(), GET),
                  new EnumNameMap.Node<HttpMethod>(HEAD.toString(), HEAD),
                  new EnumNameMap.Node<HttpMethod>(POST.toString(), POST),
                  new EnumNameMap.Node<HttpMethod>(PUT.toString(), PUT),
                  new EnumNameMap.Node<HttpMethod>(PATCH.toString(), PATCH),
                  new EnumNameMap.Node<HttpMethod>(DELETE.toString(), DELETE),
                  new EnumNameMap.Node<HttpMethod>(TRACE.toString(), TRACE),
                 new EnumNameMap.Node<HttpMethod>(CONNECT.toString(), CONNECT));
     }
 
     /**
      * Returns the {@link HttpMethod} represented by the specified name.
      * If the specified name is a standard HTTP method name, a cached instance
      * will be returned.  Otherwise, a new instance will be returned.
      */
     public static HttpMethod valueOf(String name) {
         // fast-path
         if (name == HttpMethod.GET.name()) {
             return HttpMethod.GET;
         }
         if (name == HttpMethod.POST.name()) {
             return HttpMethod.POST;
         }
         // "slow"-path
         HttpMethod result = methodMap.get(name);
         return result != null ? result : new HttpMethod(name);
     }
 
     private final AsciiString name;
 
     /**
      * Creates a new HTTP method with the specified name.  You will not need to
      * create a new method unless you are implementing a protocol derived from
      * HTTP, such as
      * <a href="https://en.wikipedia.org/wiki/Real_Time_Streaming_Protocol">RTSP</a> and
      * <a href="https://en.wikipedia.org/wiki/Internet_Content_Adaptation_Protocol">ICAP</a>
      */
     public HttpMethod(String name) {
         name = checkNonEmptyAfterTrim(name, "name");
 
         for (int i = 0; i < name.length(); i ++) {
             char c = name.charAt(i);
             if (Character.isISOControl(c) || Character.isWhitespace(c)) {
                 throw new IllegalArgumentException("invalid character in name");
             }
         }
 
         this.name = AsciiString.cached(name);
     }
 
     /**
      * Returns the name of this method.
      */
     public String name() {
         return name.toString();
     }
 
     /**
      * Returns the name of this method.
      */
     public AsciiString asciiName() {
         return name;
     }
 
     @Override
     public int hashCode() {
         return name().hashCode();
     }
 
     @Override
     public boolean equals(Object o) {
         if (this == o) {
             return true;
         }
         if (!(o instanceof HttpMethod)) {
             return false;
         }
 
         HttpMethod that = (HttpMethod) o;
         return name().equals(that.name());
     }
 
     @Override
     public String toString() {
         return name.toString();
     }
 
     @Override
     public int compareTo(HttpMethod o) {
         if (o == this) {
             return 0;
         }
         return name().compareTo(o.name());
     }
 
     private static final class EnumNameMap<T> {
         private final EnumNameMap.Node<T>[] values;
         private final int valuesMask;
 
         EnumNameMap(EnumNameMap.Node<T>... nodes) {
             values = (EnumNameMap.Node<T>[]) new EnumNameMap.Node[findNextPositivePowerOfTwo(nodes.length)];
             valuesMask = values.length - 1;
             for (EnumNameMap.Node<T> node : nodes) {
                 int i = hashCode(node.key) & valuesMask;
                 if (values[i] != null) {
                     throw new IllegalArgumentException("index " + i + " collision between values: [" +
                             values[i].key + ", " + node.key + ']');
                 }
                 values[i] = node;
             }
         }
 
         T get(String name) {
             EnumNameMap.Node<T> node = values[hashCode(name) & valuesMask];
             return node == null || !node.key.equals(name) ? null : node.value;
         }
 
         private static int hashCode(String name) {
             // This hash code needs to produce a unique index in the "values" array for each HttpMethod. If new
             // HttpMethods are added this algorithm will need to be adjusted. The constructor will "fail fast" if there
             // are duplicates detected.
             // For example with the current set of HttpMethods it just so happens that the String hash code value
             // shifted right by 6 bits modulo 16 is unique relative to all other HttpMethod values.
             return name.hashCode() >>> 6;
         }
 
         private static final class Node<T> {
             final String key;
             final T value;
 
             Node(String key, T value) {
                 this.key = key;
                 this.value = value;
             }
         }
     }
 }