/*
    * ====================================================================
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF 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
   *
   *   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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.hc.core5.http2.hpack;
  
  import org.apache.hc.core5.http.Header;
  import org.apache.hc.core5.util.Args;
  import org.apache.hc.core5.util.Asserts;
  
  final class InboundDynamicTable {
  
      private final StaticTable staticTable;
      private final FifoBuffer headers;
  
      private int maxSize;
      private int currentSize;
  
      InboundDynamicTable(final StaticTable staticTable) {
          this.staticTable = staticTable;
          this.headers = new FifoBuffer(256);
          this.maxSize = Integer.MAX_VALUE;
          this.currentSize = 0;
      }
  
      InboundDynamicTable() {
          this(StaticTable.INSTANCE);
      }
  
      public int getMaxSize() {
          return maxSize;
      }
  
      public void setMaxSize(final int maxSize) {
          this.maxSize = maxSize;
          evict();
      }
  
      public int getCurrentSize() {
          return currentSize;
      }
  
      int staticLength() {
          return staticTable.length();
      }
  
      int dynamicLength() {
          return headers.size();
      }
  
      Header getDynamicEntry(final int index) {
          return headers.get(index);
      }
  
      public int length() {
          return staticTable.length() + headers.size();
      }
  
      public HPackHeader getHeader(final int index) {
          final int length = length();
          Args.check(index >= 1, "index %s cannot be less than 1", index);
          Args.check(index <= length, "length %s cannot be greater than index %s", length, index);
          return index <= staticTable.length()
                          ? staticTable.get(index)
                          : headers.get(index - staticTable.length() - 1);
      }
  
      public void add(final HPackHeader header) {
          final int entrySize = header.getTotalSize();
          if (entrySize > this.maxSize) {
              clear();
              return;
          }
          headers.addFirst(header);
          currentSize += entrySize;
          evict();
     }
 
     private void clear() {
         currentSize = 0;
         headers.clear();
     }
 
     private void evict() {
         while (currentSize > maxSize) {
             final HPackHeader header = headers.removeLast();
             if (header != null) {
                 currentSize -= header.getTotalSize();
             } else {
                 Asserts.check(currentSize == 0, "Current table size must be zero");
                 break;
             }
         }
     }
 
 }