/*
Copyright 2014 Google Inc. All Rights Reserved.

Licensed 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.

Author: eustas.ru@gmail.com (Eugene Klyuchnikov)
*/

package io.kroki.server.decode.transcoder.zopfli;

class LongestMatchCache {

  private final static int CACHE_LENGTH = 8;

  public final char[] length;
  public final char[] dist;
  private final char[] subLenPos;
  private final byte[] subLenLen;

  LongestMatchCache(int maxBlockSize) {
    length = new char[maxBlockSize];
    dist = new char[maxBlockSize];
    subLenPos = new char[CACHE_LENGTH * maxBlockSize];
    subLenLen = new byte[CACHE_LENGTH * maxBlockSize];
  }

  void init(int blockSize) {
    Cookie.fill0(dist, blockSize);
    int n = blockSize << 3; // * CACHE_LENGTH
    char[] subLenPos = this.subLenPos;
    byte[] subLenLen = this.subLenLen;
    char[] length = this.length;

    char[] charZeroes = Cookie.charZeroes;
    byte[] byteZeroes = Cookie.byteZeroes;
    char[] charOnes = Cookie.charOnes;

    int i = 0;
    while (i < n) {
      int j = i + 65536;
      if (j > n) {
        j = n;
      }
      int l = j - i;
      System.arraycopy(byteZeroes, 0, subLenLen, i, l);
      System.arraycopy(charZeroes, 0, subLenPos, i, l);
      i = j;
    }

    i = 0;
    while (i < blockSize) {
      int j = i + 65536;
      if (j > blockSize) {
        j = blockSize;
      }
      int l = j - i;
      System.arraycopy(charOnes, 0, length, i, l);
      System.arraycopy(charZeroes, 0, subLenPos, i, l);
      i = j;
    }
  }

  void subLenToCache(char[] input, int pos, int len) {
    if (len < 3) {
      return;
    }

    int bestLength = 0;
    int j = pos * CACHE_LENGTH;
    int last = j + CACHE_LENGTH - 1;
    for (int i = 3; i <= len; ++i) {
      if (i == len || input[i] != input[i + 1]) {
        subLenPos[j] = input[i];
        subLenLen[j] = (byte) (i - 3);
        bestLength = i;
        j++;
        if (j > last) {
          break;
        }
      }
    }
    if (j <= last) {
      subLenLen[last] = (byte) (bestLength - 3);
    }
  }

  void cacheToSubLen(int pos, int len, char[] output) {
    if (len < 3) {
      return;
    }

    int maxLength = maxCachedSubLen(pos);
    int prevLength = 0;
    int j = CACHE_LENGTH * pos;
    int last = j + CACHE_LENGTH;
    for (; j < last; ++j) {
      int cLen = (subLenLen[j] & 0xFF) + 3;
      char dist = subLenPos[j];
      for (int i = prevLength; i <= cLen; ++i) {
        output[i] = dist;
      }
      if (cLen == maxLength) {
        break;
      }
      prevLength = cLen + 1;
    }
  }

  int maxCachedSubLen(int pos) {
    pos = pos * CACHE_LENGTH;
    if (subLenPos[pos] == 0) {
      return 0;
    }
    return (subLenLen[pos + CACHE_LENGTH - 1] & 0xFF) + 3;
  }
}
