/*
 * Copyright 2006 Jeremias Maerki.
 *
 * 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.
 */

package com.google.zxing.datamatrix.encoder;

/**
 * Error Correction Code for ECC200.
 */
public final class ErrorCorrection {

  /**
   * Lookup table which factors to use for which number of error correction codewords.
   * See FACTORS.
   */
  private static final int[] FACTOR_SETS
      = {5, 7, 10, 11, 12, 14, 18, 20, 24, 28, 36, 42, 48, 56, 62, 68};

  /**
   * Precomputed polynomial factors for ECC 200.
   */
  private static final int[][] FACTORS = {
      {228, 48, 15, 111, 62},
      {23, 68, 144, 134, 240, 92, 254},
      {28, 24, 185, 166, 223, 248, 116, 255, 110, 61},
      {175, 138, 205, 12, 194, 168, 39, 245, 60, 97, 120},
      {41, 153, 158, 91, 61, 42, 142, 213, 97, 178, 100, 242},
      {156, 97, 192, 252, 95, 9, 157, 119, 138, 45, 18, 186, 83, 185},
      {83, 195, 100, 39, 188, 75, 66, 61, 241, 213, 109, 129, 94, 254, 225, 48, 90, 188},
      {15, 195, 244, 9, 233, 71, 168, 2, 188, 160, 153, 145, 253, 79, 108, 82, 27, 174, 186, 172},
      {52, 190, 88, 205, 109, 39, 176, 21, 155, 197, 251, 223, 155, 21, 5, 172,
          254, 124, 12, 181, 184, 96, 50, 193},
      {211, 231, 43, 97, 71, 96, 103, 174, 37, 151, 170, 53, 75, 34, 249, 121,
          17, 138, 110, 213, 141, 136, 120, 151, 233, 168, 93, 255},
      {245, 127, 242, 218, 130, 250, 162, 181, 102, 120, 84, 179, 220, 251, 80, 182,
          229, 18, 2, 4, 68, 33, 101, 137, 95, 119, 115, 44, 175, 184, 59, 25,
          225, 98, 81, 112},
      {77, 193, 137, 31, 19, 38, 22, 153, 247, 105, 122, 2, 245, 133, 242, 8,
          175, 95, 100, 9, 167, 105, 214, 111, 57, 121, 21, 1, 253, 57, 54, 101,
          248, 202, 69, 50, 150, 177, 226, 5, 9, 5},
      {245, 132, 172, 223, 96, 32, 117, 22, 238, 133, 238, 231, 205, 188, 237, 87,
          191, 106, 16, 147, 118, 23, 37, 90, 170, 205, 131, 88, 120, 100, 66, 138,
          186, 240, 82, 44, 176, 87, 187, 147, 160, 175, 69, 213, 92, 253, 225, 19},
      {175, 9, 223, 238, 12, 17, 220, 208, 100, 29, 175, 170, 230, 192, 215, 235,
          150, 159, 36, 223, 38, 200, 132, 54, 228, 146, 218, 234, 117, 203, 29, 232,
          144, 238, 22, 150, 201, 117, 62, 207, 164, 13, 137, 245, 127, 67, 247, 28,
          155, 43, 203, 107, 233, 53, 143, 46},
      {242, 93, 169, 50, 144, 210, 39, 118, 202, 188, 201, 189, 143, 108, 196, 37,
          185, 112, 134, 230, 245, 63, 197, 190, 250, 106, 185, 221, 175, 64, 114, 71,
          161, 44, 147, 6, 27, 218, 51, 63, 87, 10, 40, 130, 188, 17, 163, 31,
          176, 170, 4, 107, 232, 7, 94, 166, 224, 124, 86, 47, 11, 204},
      {220, 228, 173, 89, 251, 149, 159, 56, 89, 33, 147, 244, 154, 36, 73, 127,
          213, 136, 248, 180, 234, 197, 158, 177, 68, 122, 93, 213, 15, 160, 227, 236,
          66, 139, 153, 185, 202, 167, 179, 25, 220, 232, 96, 210, 231, 136, 223, 239,
          181, 241, 59, 52, 172, 25, 49, 232, 211, 189, 64, 54, 108, 153, 132, 63,
          96, 103, 82, 186}};

  private static final int MODULO_VALUE = 0x12D;

  private static final int[] LOG;
  private static final int[] ALOG;

  static {
    //Create log and antilog table
    LOG = new int[256];
    ALOG = new int[255];

    int p = 1;
    for (int i = 0; i < 255; i++) {
      ALOG[i] = p;
      LOG[p] = i;
      p *= 2;
      if (p >= 256) {
        p ^= MODULO_VALUE;
      }
    }
  }

  private ErrorCorrection() {
  }

  /**
   * Creates the ECC200 error correction for an encoded message.
   *
   * @param codewords  the codewords
   * @param symbolInfo information about the symbol to be encoded
   * @return the codewords with interleaved error correction.
   */
  public static String encodeECC200(String codewords, SymbolInfo symbolInfo) {
    if (codewords.length() != symbolInfo.getDataCapacity()) {
      throw new IllegalArgumentException(
          "The number of codewords does not match the selected symbol");
    }
    StringBuilder sb = new StringBuilder(symbolInfo.getDataCapacity() + symbolInfo.getErrorCodewords());
    sb.append(codewords);
    int blockCount = symbolInfo.getInterleavedBlockCount();
    if (blockCount == 1) {
      String ecc = createECCBlock(codewords, symbolInfo.getErrorCodewords());
      sb.append(ecc);
    } else {
      sb.setLength(sb.capacity());
      int[] dataSizes = new int[blockCount];
      int[] errorSizes = new int[blockCount];
      int[] startPos = new int[blockCount];
      for (int i = 0; i < blockCount; i++) {
        dataSizes[i] = symbolInfo.getDataLengthForInterleavedBlock(i + 1);
        errorSizes[i] = symbolInfo.getErrorLengthForInterleavedBlock(i + 1);
        startPos[i] = 0;
        if (i > 0) {
          startPos[i] = startPos[i - 1] + dataSizes[i];
        }
      }
      for (int block = 0; block < blockCount; block++) {
        StringBuilder temp = new StringBuilder(dataSizes[block]);
        for (int d = block; d < symbolInfo.getDataCapacity(); d += blockCount) {
          temp.append(codewords.charAt(d));
        }
        String ecc = createECCBlock(temp.toString(), errorSizes[block]);
        int pos = 0;
        for (int e = block; e < errorSizes[block] * blockCount; e += blockCount) {
          sb.setCharAt(symbolInfo.getDataCapacity() + e, ecc.charAt(pos++));
        }
      }
    }
    return sb.toString();

  }

  private static String createECCBlock(CharSequence codewords, int numECWords) {
    return createECCBlock(codewords, 0, codewords.length(), numECWords);
  }

  private static String createECCBlock(CharSequence codewords, int start, int len, int numECWords) {
    int table = -1;
    for (int i = 0; i < FACTOR_SETS.length; i++) {
      if (FACTOR_SETS[i] == numECWords) {
        table = i;
        break;
      }
    }
    if (table < 0) {
      throw new IllegalArgumentException(
          "Illegal number of error correction codewords specified: " + numECWords);
    }
    int[] poly = FACTORS[table];
    char[] ecc = new char[numECWords];
    for (int i = 0; i < numECWords; i++) {
      ecc[i] = 0;
    }
    for (int i = start; i < start + len; i++) {
      int m = ecc[numECWords - 1] ^ codewords.charAt(i);
      for (int k = numECWords - 1; k > 0; k--) {
        if (m != 0 && poly[k] != 0) {
          ecc[k] = (char) (ecc[k - 1] ^ ALOG[(LOG[m] + LOG[poly[k]]) % 255]);
        } else {
          ecc[k] = ecc[k - 1];
        }
      }
      if (m != 0 && poly[0] != 0) {
        ecc[0] = (char) ALOG[(LOG[m] + LOG[poly[0]]) % 255];
      } else {
        ecc[0] = 0;
      }
    }
    char[] eccReversed = new char[numECWords];
    for (int i = 0; i < numECWords; i++) {
      eccReversed[i] = ecc[numECWords - i - 1];
    }
    return String.valueOf(eccReversed);
  }

}
