/*
 * Copyright 2008 ZXing authors
 *
 * 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.
 */

using System;

namespace ZXing.Datamatrix.Internal
{
    /// <summary>
    /// <p>Encapsulates a block of data within a Data Matrix Code. Data Matrix Codes may split their data into
    /// multiple blocks, each of which is a unit of data and error-correction codewords. Each
    /// is represented by an instance of this class.</p>
    ///
    /// <author>bbrown@google.com (Brian Brown)</author>
    /// </summary>
    internal sealed class DataBlock
    {
        private readonly int numDataCodewords;
        private readonly byte[] codewords;

        private DataBlock(int numDataCodewords, byte[] codewords)
        {
            this.numDataCodewords = numDataCodewords;
            this.codewords = codewords;
        }

        /// <summary>
        /// <p>When Data Matrix Codes use multiple data blocks, they actually interleave the bytes of each of them.
        /// That is, the first byte of data block 1 to n is written, then the second bytes, and so on. This
        /// method will separate the data into original blocks.</p>
        ///
        /// <param name="rawCodewords">bytes as read directly from the Data Matrix Code</param>
        /// <param name="version">version of the Data Matrix Code</param>
        /// <returns>DataBlocks containing original bytes, "de-interleaved" from representation in the</returns>
        ///         Data Matrix Code
        /// </summary>
        internal static DataBlock[] getDataBlocks(byte[] rawCodewords,
                                                  Version version)
        {
            // Figure out the number and size of data blocks used by this version
            Version.ECBlocks ecBlocks = version.getECBlocks();

            // First count the total number of data blocks
            int totalBlocks = 0;
            Version.ECB[] ecBlockArray = ecBlocks.ECBlocksValue;
            foreach (Version.ECB ecBlock in ecBlockArray)
            {
                totalBlocks += ecBlock.Count;
            }

            // Now establish DataBlocks of the appropriate size and number of data codewords
            DataBlock[] result = new DataBlock[totalBlocks];
            int numResultBlocks = 0;
            foreach (Version.ECB ecBlock in ecBlockArray)
            {
                for (int i = 0; i < ecBlock.Count; i++)
                {
                    int numDataCodewords = ecBlock.DataCodewords;
                    int numBlockCodewords = ecBlocks.ECCodewords + numDataCodewords;
                    result[numResultBlocks++] = new DataBlock(numDataCodewords, new byte[numBlockCodewords]);
                }
            }

            // All blocks have the same amount of data, except that the last n
            // (where n may be 0) have 1 less byte. Figure out where these start.
            // TODO(bbrown): There is only one case where there is a difference for Data Matrix for size 144
            int longerBlocksTotalCodewords = result[0].codewords.Length;
            //int shorterBlocksTotalCodewords = longerBlocksTotalCodewords - 1;

            int longerBlocksNumDataCodewords = longerBlocksTotalCodewords - ecBlocks.ECCodewords;
            int shorterBlocksNumDataCodewords = longerBlocksNumDataCodewords - 1;
            // The last elements of result may be 1 element shorter for 144 matrix
            // first fill out as many elements as all of them have minus 1
            int rawCodewordsOffset = 0;
            for (int i = 0; i < shorterBlocksNumDataCodewords; i++)
            {
                for (int j = 0; j < numResultBlocks; j++)
                {
                    result[j].codewords[i] = rawCodewords[rawCodewordsOffset++];
                }
            }

            // Fill out the last data block in the longer ones
            bool specialVersion = version.getVersionNumber() == 24;
            int numLongerBlocks = specialVersion ? 8 : numResultBlocks;
            for (int j = 0; j < numLongerBlocks; j++)
            {
                result[j].codewords[longerBlocksNumDataCodewords - 1] = rawCodewords[rawCodewordsOffset++];
            }

            // Now add in error correction blocks
            int max = result[0].codewords.Length;
            for (int i = longerBlocksNumDataCodewords; i < max; i++)
            {
                for (int j = 0; j < numResultBlocks; j++)
                {
                    int jOffset = specialVersion ? (j + 8) % numResultBlocks : j;
                    int iOffset = specialVersion && jOffset > 7 ? i - 1 : i;
                    result[jOffset].codewords[iOffset] = rawCodewords[rawCodewordsOffset++];
                }
            }

            if (rawCodewordsOffset != rawCodewords.Length)
            {
                throw new ArgumentException();
            }

            return result;
        }

        internal int NumDataCodewords
        {
            get { return numDataCodewords; }
        }

        internal byte[] Codewords
        {
            get { return codewords; }
        }
    }
}
