/*
 * 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;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using com.google.zxing.common; 

namespace com.google.zxing.datamatrix.decoder
{
    /**
     * <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)
     */
    public sealed class DecodedBitStreamParser
    {
           /**
           * See ISO 16022:2006, Annex C Table C.1
           * The C40 Basic Character Set (*'s used for placeholders for the shift values)
           */
          private static  char[] C40_BASIC_SET_CHARS = {
              '*', '*', '*', ' ', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
              'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
              'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'
          };
          
          private static  char[] C40_SHIFT2_SET_CHARS = {
            '!', '"', '#', '$', '%', '&', '\'', '(', ')', '*', '+', ',', '-', '.',
            '/', ':', ';', '<', '=', '>', '?', '@', '[', '\\', ']', '^', '_'
	        };
          
          /**
           * See ISO 16022:2006, Annex C Table C.2
           * The Text Basic Character Set (*'s used for placeholders for the shift values)
           */
          private static  char[] TEXT_BASIC_SET_CHARS = {
            '*', '*', '*', ' ', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
            'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
            'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'
          };
          
          private static  char[] TEXT_SHIFT3_SET_CHARS = {
            '\'', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
            'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '{', '|', '}', '~', (char) 127
          };
          
          private const  int PAD_ENCODE = 0;  // Not really an encoding
          private const int ASCII_ENCODE = 1;
          private const int C40_ENCODE = 2;
          private const int TEXT_ENCODE = 3;
          private const int ANSIX12_ENCODE = 4;
          private const int EDIFACT_ENCODE = 5;
          private const int BASE256_ENCODE = 6;

          private DecodedBitStreamParser() {
          }

          public static DecoderResult decode(sbyte[] bytes) {
            BitSource bits = new BitSource(bytes);
            StringBuilder result = new StringBuilder();
            StringBuilder resultTrailer = new StringBuilder(0);
            System.Collections.ArrayList byteSegments = new System.Collections.ArrayList(1);
            int mode = ASCII_ENCODE;
            do {
              if (mode == ASCII_ENCODE) {
                mode = decodeAsciiSegment(bits, result, resultTrailer);
              } else {
                switch (mode) {
                  case C40_ENCODE:
                    decodeC40Segment(bits, result);
                    break;
                  case TEXT_ENCODE:
                    decodeTextSegment(bits, result);
                    break;
                  case ANSIX12_ENCODE:
                    decodeAnsiX12Segment(bits, result);
                    break;
                  case EDIFACT_ENCODE:
                    decodeEdifactSegment(bits, result);
                    break;
                  case BASE256_ENCODE:
                    decodeBase256Segment(bits, result, byteSegments);
                    break;
                  default:
                    throw new ReaderException();
                }
                mode = ASCII_ENCODE;
              }
            } while (mode != PAD_ENCODE && bits.available() > 0);
            if (resultTrailer.Length > 0) {
              result.Append(resultTrailer);
            }
            return new DecoderResult(bytes, result.ToString(), int.Equals(byteSegments.Count,0) ? null : byteSegments);
          }
          
          /**
           * See ISO 16022:2006, 5.2.3 and Annex C, Table C.2
           */
          private static int decodeAsciiSegment(BitSource bits, StringBuilder result, StringBuilder resultTrailer)
              {
            bool upperShift = false;
            do {
              int oneByte = bits.readBits(8);
              if (oneByte == 0) {
	    	        throw new ReaderException();
	            } else if (oneByte <= 128) {  // ASCII data (ASCII value + 1)
	    	        oneByte = upperShift ? (oneByte + 128) : oneByte;
	    	        upperShift = false;
	    	        result.Append((char) (oneByte - 1));
	    	        return ASCII_ENCODE;
	            } else if (oneByte == 129) {  // Pad
	    	        return PAD_ENCODE;
	            } else if (oneByte <= 229) {  // 2-digit data 00-99 (Numeric Value + 130)
	              int value = oneByte - 130;
	              if (value < 10) { // padd with '0' for single digit values
	                result.Append('0');
	              }
	    	        result.Append(value);
	            } else if (oneByte == 230) {  // Latch to C40 encodation
	    	        return C40_ENCODE;
	            } else if (oneByte == 231) {  // Latch to Base 256 encodation
	    	        return BASE256_ENCODE;
	            } else if (oneByte == 232) {  // FNC1
	    	        throw new ReaderException();
	            } else if (oneByte == 233) {  // Structured Append
	    	        throw new ReaderException();
	            } else if (oneByte == 234) {  // Reader Programming
	    	        throw new ReaderException();
	            } else if (oneByte == 235) {  // Upper Shift (shift to Extended ASCII)
	    	        upperShift = true;
	            } else if (oneByte == 236) {  // 05 Macro
                result.Append("[)>\u001E05\u001D");
                resultTrailer.Insert(0, "\u001E\u0004");
              } else if (oneByte == 237) {  // 06 Macro
	    	        result.Append("[)>\u001E06\u001D");
                resultTrailer.Insert(0, "\u001E\u0004");
	            } else if (oneByte == 238) {  // Latch to ANSI X12 encodation
	    	        return ANSIX12_ENCODE;
	            } else if (oneByte == 239) {  // Latch to Text encodation
	    	        return TEXT_ENCODE;
	            } else if (oneByte == 240) {  // Latch to EDIFACT encodation
	    	        return EDIFACT_ENCODE;
	            } else if (oneByte == 241) {  // ECI Character
	    	        // TODO(bbrown): I think we need to support ECI
	    	        throw new ReaderException();
	            } else if (oneByte >= 242) {  // Not to be used in ASCII encodation
	    	        throw new ReaderException();
	            }
            } while (bits.available() > 0);
            return ASCII_ENCODE;
          }

          /**
           * See ISO 16022:2006, 5.2.5 and Annex C, Table C.1
           */
          private static void decodeC40Segment(BitSource bits, StringBuilder result) {
            // Three C40 values are encoded in a 16-bit value as
            // (1600 * C1) + (40 * C2) + C3 + 1
            // TODO(bbrown): The Upper Shift with C40 doesn't work in the 4 value scenario all the time
            bool upperShift = false;

            int[] cValues = new int[3];
            do {
              // If there is only one byte left then it will be encoded as ASCII
              if (bits.available() == 8) {
                return;
              }
              int firstByte = bits.readBits(8);
              if (firstByte == 254) {  // Unlatch codeword
                return;
              }

              parseTwoBytes(firstByte, bits.readBits(8), cValues);

              int shift = 0;
              for (int i = 0; i < 3; i++) {
                int cValue = cValues[i];
                switch (shift) {
                  case 0:
                    if (cValue < 3) {
                      shift = cValue + 1;
                    } else {
                      if (upperShift) {
                        result.Append((char) (C40_BASIC_SET_CHARS[cValue] + 128));
                        upperShift = false;
                      } else {
                        result.Append(C40_BASIC_SET_CHARS[cValue]);
                      }
                    }
                    break;
                  case 1:
                    if (upperShift) {
                      result.Append((char) (cValue + 128));
                      upperShift = false;
                    } else {
                      result.Append(cValue);
                    }
                    shift = 0;
                    break;
                  case 2:
                    if (cValue < 27) {
                      if (upperShift) {
                        result.Append((char) (C40_SHIFT2_SET_CHARS[cValue] + 128));
                        upperShift = false;
                      } else {
                        result.Append(C40_SHIFT2_SET_CHARS[cValue]);
                      }
                    } else if (cValue == 27) {  // FNC1
                      throw new ReaderException();
                    } else if (cValue == 30) {  // Upper Shift
                      upperShift = true;
                    } else {
                      throw new ReaderException();
                    }
                    shift = 0;
                    break;
                  case 3:
                    if (upperShift) {
                      result.Append((char) (cValue + 224));
                      upperShift = false;
                    } else {
                      result.Append((char) (cValue + 96));
                    }
                    shift = 0;
                    break;
                  default:
                    throw new ReaderException();
                }
              }
            } while (bits.available() > 0);
          }
          
          /**
           * See ISO 16022:2006, 5.2.6 and Annex C, Table C.2
           */
          private static void decodeTextSegment(BitSource bits, StringBuilder result) {
            // Three Text values are encoded in a 16-bit value as
            // (1600 * C1) + (40 * C2) + C3 + 1
            // TODO(bbrown): The Upper Shift with Text doesn't work in the 4 value scenario all the time
            bool upperShift = false;

            int[] cValues = new int[3];
            do {
              // If there is only one byte left then it will be encoded as ASCII
              if (bits.available() == 8) {
                return;
              }
              int firstByte = bits.readBits(8);
              if (firstByte == 254) {  // Unlatch codeword
                return;
              }

              parseTwoBytes(firstByte, bits.readBits(8), cValues);

              int shift = 0;
              for (int i = 0; i < 3; i++) {
                int cValue = cValues[i];
                switch (shift) {
                  case 0:
                    if (cValue < 3) {
                      shift = cValue + 1;
                    } else {
                      if (upperShift) {
                        result.Append((char) (TEXT_BASIC_SET_CHARS[cValue] + 128));
                        upperShift = false;
                      } else {
                        result.Append(TEXT_BASIC_SET_CHARS[cValue]);
                      }
                    }
                    break;
                  case 1:
                    if (upperShift) {
                      result.Append((char) (cValue + 128));
                      upperShift = false;
                    } else {
                      result.Append(cValue);
                    }
                    shift = 0;
                    break;
                  case 2:
                    // Shift 2 for Text is the same encoding as C40
                    if (cValue < 27) {
                      if (upperShift) {
                        result.Append((char) (C40_SHIFT2_SET_CHARS[cValue] + 128));
                        upperShift = false;
                      } else {
                        result.Append(C40_SHIFT2_SET_CHARS[cValue]);
                      }
                    } else if (cValue == 27) {  // FNC1
                      throw new ReaderException();
                    } else if (cValue == 30) {  // Upper Shift
                      upperShift = true;
                    } else {
                      throw new ReaderException();
                    }
                    shift = 0;
                    break;
                  case 3:
                    if (upperShift) {
                      result.Append((char) (TEXT_SHIFT3_SET_CHARS[cValue] + 128));
                      upperShift = false;
                    } else {
                      result.Append(TEXT_SHIFT3_SET_CHARS[cValue]);
                    }
                    shift = 0;
                    break;
                  default:
                    throw new ReaderException();
                }
              }
            } while (bits.available() > 0);
          }
          
          /**
           * See ISO 16022:2006, 5.2.7
           */
          private static void decodeAnsiX12Segment(BitSource bits, StringBuilder result) {
            // Three ANSI X12 values are encoded in a 16-bit value as
            // (1600 * C1) + (40 * C2) + C3 + 1

            int[] cValues = new int[3];
            do {
              // If there is only one byte left then it will be encoded as ASCII
              if (bits.available() == 8) {
                return;
              }
              int firstByte = bits.readBits(8);
              if (firstByte == 254) {  // Unlatch codeword
                return;
              }

              parseTwoBytes(firstByte, bits.readBits(8), cValues);

              for (int i = 0; i < 3; i++) {
                int cValue = cValues[i];
                if (cValue == 0) {  // X12 segment terminator <CR>
                  result.Append('\r');
                } else if (cValue == 1) {  // X12 segment separator *
                  result.Append('*');
                } else if (cValue == 2) {  // X12 sub-element separator >
                  result.Append('>');
                } else if (cValue == 3) {  // space
                  result.Append(' ');
                } else if (cValue < 14) {  // 0 - 9
                  result.Append((char) (cValue + 44));
                } else if (cValue < 40) {  // A - Z
                  result.Append((char) (cValue + 51));
                } else {
                  throw new ReaderException();
                }
              }
            } while (bits.available() > 0);
          }

          private static void parseTwoBytes(int firstByte, int secondByte, int[] result) {
            int fullBitValue = (firstByte << 8) + secondByte - 1;
            int temp = fullBitValue / 1600;
            result[0] = temp;
            fullBitValue -= temp * 1600;
            temp = fullBitValue / 40;
            result[1] = temp;
            result[2] = fullBitValue - temp * 40;
          }
          
          /**
           * See ISO 16022:2006, 5.2.8 and Annex C Table C.3
           */
          private static void decodeEdifactSegment(BitSource bits, StringBuilder result) {
            bool unlatch = false;
            do {
              // If there is only two or less bytes left then it will be encoded as ASCII
              if (bits.available() <= 16) {
                return;
              }

              for (int i = 0; i < 4; i++) {
                int edifactValue = bits.readBits(6);

                // Check for the unlatch character
                if (edifactValue == 0x2B67) {  // 011111
                  unlatch = true;
                  // If we encounter the unlatch code then continue reading because the Codeword triple
                  // is padded with 0's
                }
                
                if (!unlatch) {
                  if ((edifactValue & 32) == 0) {  // no 1 in the leading (6th) bit
                    edifactValue |= 64;  // Add a leading 01 to the 6 bit binary value
                  }
                  result.Append(edifactValue);
                }
              }
            } while (!unlatch && bits.available() > 0);
          }
          
          /**
           * See ISO 16022:2006, 5.2.9 and Annex B, B.2
           */
          private static void decodeBase256Segment(BitSource bits, StringBuilder result, System.Collections.ArrayList byteSegments) {
            // Figure out how long the Base 256 Segment is.
            int d1 = bits.readBits(8);
            int count;
            if (d1 == 0) {  // Read the remainder of the symbol
              count = bits.available() / 8;
            } else if (d1 < 250) {
              count = d1;
            } else {
              count = 250 * (d1 - 249) + bits.readBits(8);
            }
            byte[] bytes = new byte[count];
            for (int i = 0; i < count; i++) {
              bytes[i] = unrandomize255State(bits.readBits(8), i);
            }
            byteSegments.Add(bytes);
            try {
                result.Append(System.Text.Encoding.GetEncoding("iso-8859-1").GetString(bytes));
            } catch (Exception uee) {
              throw new Exception("Platform does not support required encoding: " + uee);
            }
          }
          
          /**
           * See ISO 16022:2006, Annex B, B.2
           */
          private static byte unrandomize255State(int randomizedBase256Codeword,
                                                  int base256CodewordPosition) {
            int pseudoRandomNumber = ((149 * base256CodewordPosition) % 255) + 1;
            int tempVariable = randomizedBase256Codeword - pseudoRandomNumber;
            return (byte) (tempVariable >= 0 ? tempVariable : (tempVariable + 256));
          }
    }
}