/* Copyright 2015 Google Inc. All Rights Reserved.
   
      Distributed under MIT license.
      See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
   */
   
   package org.htmlunit.util.brotli;
   
   import java.nio.ByteBuffer;
  
  /**
   * Collection of static dictionary words.
   *
   * <p>Dictionary content is loaded from binary resource when {@link #getData()} is executed for the
   * first time. Consequently, it saves memory and CPU in case dictionary is not required.
   *
   * <p>One possible drawback is that multiple threads that need dictionary data may be blocked (only
   * once in each classworld). To avoid this, it is enough to call {@link #getData()} proactively.
   */
  public final class Dictionary {
    static final int MIN_DICTIONARY_WORD_LENGTH = 4;
    static final int MAX_DICTIONARY_WORD_LENGTH = 31;
  
    private static ByteBuffer data = ByteBuffer.allocateDirect(0);
    static final int[] offsets = new int[32];
    static final int[] sizeBits = new int[32];
  
    private static class DataLoader {
      static final boolean OK;
  
      static {
        boolean ok = true;
        try {
          Class.forName(Dictionary.class.getPackage().getName() + ".DictionaryData");
        } catch (Throwable ex) {
          ok = false;
        }
        OK = ok;
      }
    }
  
    private static final int DICTIONARY_DEBUG = Utils.isDebugMode();
  
    public static void setData(ByteBuffer newData, int[] newSizeBits) {
      if (DICTIONARY_DEBUG != 0) {
        if ((Utils.isDirect(newData) == 0) || (Utils.isReadOnly(newData) == 0)) {
          throw new BrotliRuntimeException("newData must be a direct read-only byte buffer");
        }
        // TODO: is that so?
        if (newSizeBits.length > MAX_DICTIONARY_WORD_LENGTH) {
          throw new BrotliRuntimeException(
              "sizeBits length must be at most " + String.valueOf(MAX_DICTIONARY_WORD_LENGTH));
        }
        for (int i = 0; i < MIN_DICTIONARY_WORD_LENGTH; ++i) {
          if (newSizeBits[i] != 0) {
            throw new BrotliRuntimeException(
                "first " + String.valueOf(MIN_DICTIONARY_WORD_LENGTH) + " must be 0");
          }
        }
      }
      final int[] dictionaryOffsets = Dictionary.offsets;
      final int[] dictionarySizeBits = Dictionary.sizeBits;
      for (int i = 0; i < newSizeBits.length; ++i) {
        dictionarySizeBits[i] = newSizeBits[i];
      }
      int pos = 0;
      for (int i = 0; i < newSizeBits.length; ++i) {
        dictionaryOffsets[i] = pos;
        final int bits = dictionarySizeBits[i];
        if (bits != 0) {
          pos += i << (bits & 31);
          if (DICTIONARY_DEBUG != 0) {
            if (bits >= 31) {
              throw new BrotliRuntimeException("newSizeBits values must be less than 31");
            }
            if (pos <= 0 || pos > newData.capacity()) {
              throw new BrotliRuntimeException("newSizeBits is inconsistent: overflow");
            }
          }
        }
      }
      for (int i = newSizeBits.length; i < 32; ++i) {
        dictionaryOffsets[i] = pos;
      }
      if (DICTIONARY_DEBUG != 0) {
        if (pos != newData.capacity()) {
          throw new BrotliRuntimeException("newSizeBits is inconsistent: underflow");
        }
      }
      Dictionary.data = newData;
    }
  
    public static ByteBuffer getData() {
      if (data.capacity() != 0) {
        return data;
      }
      if (!DataLoader.OK) {
        throw new BrotliRuntimeException("brotli dictionary is not set");
      }
     /* Might have been set when {@link DictionaryData} was loaded.*/
     return data;
   }
 }