/*
    * Copyright 2015 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.channel;
  
  import io.netty5.buffer.api.Buffer;
  import io.netty5.buffer.api.BufferAllocator;
  
  import java.util.function.Predicate;
  
  import static io.netty5.util.internal.ObjectUtil.checkPositive;
  
  /**
   * Default implementation of {@link MaxMessagesRecvBufferAllocator} which respects {@link ChannelOption#AUTO_READ}
   * and also prevents overflow.
   */
  public abstract class DefaultMaxMessagesRecvBufferAllocator implements MaxMessagesRecvBufferAllocator {
      private final boolean ignoreBytesRead;
      private volatile int maxMessagesPerRead;
      private volatile boolean respectMaybeMoreData = true;
  
      protected DefaultMaxMessagesRecvBufferAllocator() {
          this(1);
      }
  
      protected DefaultMaxMessagesRecvBufferAllocator(int maxMessagesPerRead) {
          this(maxMessagesPerRead, false);
      }
  
      DefaultMaxMessagesRecvBufferAllocator(int maxMessagesPerRead, boolean ignoreBytesRead) {
          this.ignoreBytesRead = ignoreBytesRead;
          maxMessagesPerRead(maxMessagesPerRead);
      }
  
      @Override
      public int maxMessagesPerRead() {
          return maxMessagesPerRead;
      }
  
      @Override
      public MaxMessagesRecvBufferAllocator maxMessagesPerRead(int maxMessagesPerRead) {
          checkPositive(maxMessagesPerRead, "maxMessagesPerRead");
          this.maxMessagesPerRead = maxMessagesPerRead;
          return this;
      }
  
      /**
       * Focuses on enforcing the maximum messages per read condition for {@link #continueReading(boolean)}.
       */
      public abstract class MaxMessageHandle implements Handle {
          private int maxMessagePerRead;
          private int totalMessages;
          private int totalBytesRead;
          private int attemptedBytesRead;
          private int lastBytesRead;
  
          private final Predicate<Handle> defaultMaybeMoreSupplier = h -> attemptedBytesRead == lastBytesRead;
  
          /**
           * Only {@link ChannelOption#MAX_MESSAGES_PER_READ} is used.
           */
          @Override
          public void reset() {
              maxMessagePerRead = maxMessagesPerRead();
              totalMessages = totalBytesRead = 0;
          }
  
          @Override
          public Buffer allocate(BufferAllocator alloc) {
              return alloc.allocate(guess());
          }
  
          @Override
          public final void incMessagesRead(int amt) {
              totalMessages += amt;
          }
  
          @Override
          public void lastBytesRead(int bytes) {
              lastBytesRead = bytes;
              if (bytes > 0) {
                  totalBytesRead += bytes;
              }
          }
  
          @Override
          public final int lastBytesRead() {
             return lastBytesRead;
         }
 
         @Override
         public boolean continueReading(boolean autoRead) {
             return continueReading(autoRead, defaultMaybeMoreSupplier);
         }
 
         @Override
         public boolean continueReading(boolean autoRead, Predicate<Handle> maybeMoreDataSupplier) {
             return autoRead && maybeMoreDataSupplier.test(this) &&
                    totalMessages < maxMessagePerRead && (ignoreBytesRead || totalBytesRead > 0);
         }
 
         @Override
         public void readComplete() {
         }
 
         @Override
         public int attemptedBytesRead() {
             return attemptedBytesRead;
         }
 
         @Override
         public void attemptedBytesRead(int bytes) {
             attemptedBytesRead = bytes;
         }
 
         protected final int totalBytesRead() {
             return totalBytesRead < 0 ? Integer.MAX_VALUE : totalBytesRead;
         }
     }
 }