/*
    * Copyright 2014 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.netty5.handler.codec.http2;
  
  import io.netty5.util.internal.UnstableApi;
  
  /**
   * Provides utility methods for accessing specific flags as defined by the HTTP/2 spec.
   */
  @UnstableApi
  public final class Http2Flags {
      public static final short END_STREAM = 0x1;
      public static final short END_HEADERS = 0x4;
      public static final short ACK = 0x1;
      public static final short PADDED = 0x8;
      public static final short PRIORITY = 0x20;
  
      private short value;
  
      public Http2Flags() {
      }
  
      public Http2Flags(short value) {
          this.value = value;
      }
  
      /**
       * Gets the underlying flags value.
       */
      public short value() {
          return value;
      }
  
      /**
       * Determines whether the {@link #END_STREAM} flag is set. Only applies to DATA and HEADERS
       * frames.
       */
      public boolean endOfStream() {
          return isFlagSet(END_STREAM);
      }
  
      /**
       * Determines whether the {@link #END_HEADERS} flag is set. Only applies for HEADERS,
       * PUSH_PROMISE, and CONTINUATION frames.
       */
      public boolean endOfHeaders() {
          return isFlagSet(END_HEADERS);
      }
  
      /**
       * Determines whether the flag is set indicating the presence of the exclusive, stream
       * dependency, and weight fields in a HEADERS frame.
       */
      public boolean priorityPresent() {
          return isFlagSet(PRIORITY);
      }
  
      /**
       * Determines whether the flag is set indicating that this frame is an ACK. Only applies for
       * SETTINGS and PING frames.
       */
      public boolean ack() {
          return isFlagSet(ACK);
      }
  
      /**
       * For frames that include padding, indicates if the {@link #PADDED} field is present. Only
       * applies to DATA, HEADERS, PUSH_PROMISE and CONTINUATION frames.
       */
      public boolean paddingPresent() {
          return isFlagSet(PADDED);
      }
  
      /**
       * Gets the number of bytes expected for the priority fields of the payload. This is determined
       * by the {@link #priorityPresent()} flag.
       */
      public int getNumPriorityBytes() {
          return priorityPresent() ? 5 : 0;
      }
  
      /**
       * Gets the length in bytes of the padding presence field expected in the payload. This is
       * determined by the {@link #paddingPresent()} flag.
       */
      public int getPaddingPresenceFieldLength() {
          return paddingPresent() ? 1 : 0;
     }
 
     /**
      * Sets the {@link #END_STREAM} flag.
      */
     public Http2Flags endOfStream(boolean endOfStream) {
         return setFlag(endOfStream, END_STREAM);
     }
 
     /**
      * Sets the {@link #END_HEADERS} flag.
      */
     public Http2Flags endOfHeaders(boolean endOfHeaders) {
         return setFlag(endOfHeaders, END_HEADERS);
     }
 
     /**
      * Sets the {@link #PRIORITY} flag.
      */
     public Http2Flags priorityPresent(boolean priorityPresent) {
         return setFlag(priorityPresent, PRIORITY);
     }
 
     /**
      * Sets the {@link #PADDED} flag.
      */
     public Http2Flags paddingPresent(boolean paddingPresent) {
         return setFlag(paddingPresent, PADDED);
     }
 
     /**
      * Sets the {@link #ACK} flag.
      */
     public Http2Flags ack(boolean ack) {
         return setFlag(ack, ACK);
     }
 
     /**
      * Generic method to set any flag.
      * @param on if the flag should be enabled or disabled.
      * @param mask the mask that identifies the bit for the flag.
      * @return this instance.
      */
     public Http2Flags setFlag(boolean on, short mask) {
         if (on) {
             value |= mask;
         } else {
             value &= ~mask;
         }
         return this;
     }
 
     /**
      * Indicates whether or not a particular flag is set.
      * @param mask the mask identifying the bit for the particular flag being tested
      * @return {@code true} if the flag is set
      */
     public boolean isFlagSet(short mask) {
         return (value & mask) != 0;
     }
 
     @Override
     public int hashCode() {
         final int prime = 31;
         int result = 1;
         result = prime * result + value;
         return result;
     }
 
     @Override
     public boolean equals(Object obj) {
         if (this == obj) {
             return true;
         }
         if (obj == null) {
             return false;
         }
         if (getClass() != obj.getClass()) {
             return false;
         }
 
         return value == ((Http2Flags) obj).value;
     }
 
     @Override
     public String toString() {
         StringBuilder builder = new StringBuilder();
         builder.append("value = ").append(value).append(" (");
         if (ack()) {
             builder.append("ACK,");
         }
         if (endOfHeaders()) {
             builder.append("END_OF_HEADERS,");
         }
         if (endOfStream()) {
             builder.append("END_OF_STREAM,");
         }
         if (priorityPresent()) {
             builder.append("PRIORITY_PRESENT,");
         }
         if (paddingPresent()) {
             builder.append("PADDING_PRESENT,");
         }
         builder.append(')');
         return builder.toString();
     }
 }