/*
 * Copyright 2010 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.
 */

package com.google.zxing.oned;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.common.BitMatrix;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;

/**
 * This object renders a CODE128 code as a {@link BitMatrix}.
 *
 * @author erik.barbara@gmail.com (Erik Barbara)
 */
public final class Code128Writer extends OneDimensionalCodeWriter {

  private static final int CODE_START_A = 103;
  private static final int CODE_START_B = 104;
  private static final int CODE_START_C = 105;
  private static final int CODE_CODE_A = 101;
  private static final int CODE_CODE_B = 100;
  private static final int CODE_CODE_C = 99;
  private static final int CODE_STOP = 106;

  // Dummy characters used to specify control characters in input
  private static final char ESCAPE_FNC_1 = '\u00f1';
  private static final char ESCAPE_FNC_2 = '\u00f2';
  private static final char ESCAPE_FNC_3 = '\u00f3';
  private static final char ESCAPE_FNC_4 = '\u00f4';

  private static final int CODE_FNC_1 = 102;   // Code A, Code B, Code C
  private static final int CODE_FNC_2 = 97;    // Code A, Code B
  private static final int CODE_FNC_3 = 96;    // Code A, Code B
  private static final int CODE_FNC_4_A = 101; // Code A
  private static final int CODE_FNC_4_B = 100; // Code B

  // Results of minimal lookahead for code C
  private enum CType {
    UNCODABLE,
    ONE_DIGIT,
    TWO_DIGITS,
    FNC_1
  }

  @Override
  protected Collection<BarcodeFormat> getSupportedWriteFormats() {
    return Collections.singleton(BarcodeFormat.CODE_128);
  }

  @Override
  public boolean[] encode(String contents) {
    int length = contents.length();
    // Check length
    if (length < 1 || length > 80) {
      throw new IllegalArgumentException(
          "Contents length should be between 1 and 80 characters, but got " + length);
    }
    // Check content
    for (int i = 0; i < length; i++) {
      char c = contents.charAt(i);
      switch (c) {
        case ESCAPE_FNC_1:
        case ESCAPE_FNC_2:
        case ESCAPE_FNC_3:
        case ESCAPE_FNC_4:
          break;
        default:
          if (c > 127) {
            // support for FNC4 isn't implemented, no full Latin-1 character set available at the moment
            throw new IllegalArgumentException("Bad character in input: " + c);
          }
      }
    }

    Collection<int[]> patterns = new ArrayList<>(); // temporary storage for patterns
    int checkSum = 0;
    int checkWeight = 1;
    int codeSet = 0; // selected code (CODE_CODE_B or CODE_CODE_C)
    int position = 0; // position in contents

    while (position < length) {
      //Select code to use
      int newCodeSet = chooseCode(contents, position, codeSet);

      //Get the pattern index
      int patternIndex;
      if (newCodeSet == codeSet) {
        // Encode the current character
        // First handle escapes
        switch (contents.charAt(position)) {
          case ESCAPE_FNC_1:
            patternIndex = CODE_FNC_1;
            break;
          case ESCAPE_FNC_2:
            patternIndex = CODE_FNC_2;
            break;
          case ESCAPE_FNC_3:
            patternIndex = CODE_FNC_3;
            break;
          case ESCAPE_FNC_4:
            if (codeSet == CODE_CODE_A) {
              patternIndex = CODE_FNC_4_A;
            } else {
              patternIndex = CODE_FNC_4_B;
            }
            break;
          default:
            // Then handle normal characters otherwise
            switch (codeSet) {
              case CODE_CODE_A:
                patternIndex = contents.charAt(position) - ' ';
                if (patternIndex < 0) {
                  // everything below a space character comes behind the underscore in the code patterns table
                  patternIndex += '`';
                }
                break;
              case CODE_CODE_B:
                patternIndex = contents.charAt(position) - ' ';
                break;
              default:
                // CODE_CODE_C
                patternIndex = Integer.parseInt(contents.substring(position, position + 2));
                position++; // Also incremented below
                break;
            }
        }
        position++;
      } else {
        // Should we change the current code?
        // Do we have a code set?
        if (codeSet == 0) {
          // No, we don't have a code set
          switch (newCodeSet) {
            case CODE_CODE_A:
              patternIndex = CODE_START_A;
              break;
            case CODE_CODE_B:
              patternIndex = CODE_START_B;
              break;
            default:
              patternIndex = CODE_START_C;
              break;
          }
        } else {
          // Yes, we have a code set
          patternIndex = newCodeSet;
        }
        codeSet = newCodeSet;
      }

      // Get the pattern
      patterns.add(Code128Reader.CODE_PATTERNS[patternIndex]);

      // Compute checksum
      checkSum += patternIndex * checkWeight;
      if (position != 0) {
        checkWeight++;
      }
    }

    // Compute and append checksum
    checkSum %= 103;
    patterns.add(Code128Reader.CODE_PATTERNS[checkSum]);

    // Append stop code
    patterns.add(Code128Reader.CODE_PATTERNS[CODE_STOP]);

    // Compute code width
    int codeWidth = 0;
    for (int[] pattern : patterns) {
      for (int width : pattern) {
        codeWidth += width;
      }
    }

    // Compute result
    boolean[] result = new boolean[codeWidth];
    int pos = 0;
    for (int[] pattern : patterns) {
      pos += appendPattern(result, pos, pattern, true);
    }

    return result;
  }

  private static CType findCType(CharSequence value, int start) {
    int last = value.length();
    if (start >= last) {
      return CType.UNCODABLE;
    }
    char c = value.charAt(start);
    if (c == ESCAPE_FNC_1) {
      return CType.FNC_1;
    }
    if (c < '0' || c > '9') {
      return CType.UNCODABLE;
    }
    if (start + 1 >= last) {
      return CType.ONE_DIGIT;
    }
    c = value.charAt(start + 1);
    if (c < '0' || c > '9') {
      return CType.ONE_DIGIT;
    }
    return CType.TWO_DIGITS;
  }

  private static int chooseCode(CharSequence value, int start, int oldCode) {
    CType lookahead = findCType(value, start);
    if (lookahead == CType.ONE_DIGIT) {
       if (oldCode == CODE_CODE_A) {
         return CODE_CODE_A;
       }
       return CODE_CODE_B;
    }
    if (lookahead == CType.UNCODABLE) {
      if (start < value.length()) {
        char c = value.charAt(start);
        if (c < ' ' || (oldCode == CODE_CODE_A && (c < '`' || (c >= ESCAPE_FNC_1 && c <= ESCAPE_FNC_4)))) {
          // can continue in code A, encodes ASCII 0 to 95 or FNC1 to FNC4
          return CODE_CODE_A;
        }
      }
      return CODE_CODE_B; // no choice
    }
    if (oldCode == CODE_CODE_A && lookahead == CType.FNC_1) {
      return CODE_CODE_A;
    }
    if (oldCode == CODE_CODE_C) { // can continue in code C
      return CODE_CODE_C;
    }
    if (oldCode == CODE_CODE_B) {
      if (lookahead == CType.FNC_1) {
        return CODE_CODE_B; // can continue in code B
      }
      // Seen two consecutive digits, see what follows
      lookahead = findCType(value, start + 2);
      if (lookahead == CType.UNCODABLE || lookahead == CType.ONE_DIGIT) {
        return CODE_CODE_B; // not worth switching now
      }
      if (lookahead == CType.FNC_1) { // two digits, then FNC_1...
        lookahead = findCType(value, start + 3);
        if (lookahead == CType.TWO_DIGITS) { // then two more digits, switch
          return CODE_CODE_C;
        } else {
          return CODE_CODE_B; // otherwise not worth switching
        }
      }
      // At this point, there are at least 4 consecutive digits.
      // Look ahead to choose whether to switch now or on the next round.
      int index = start + 4;
      while ((lookahead = findCType(value, index)) == CType.TWO_DIGITS) {
        index += 2;
      }
      if (lookahead == CType.ONE_DIGIT) { // odd number of digits, switch later
        return CODE_CODE_B;
      }
      return CODE_CODE_C; // even number of digits, switch now
    }
    // Here oldCode == 0, which means we are choosing the initial code
    if (lookahead == CType.FNC_1) { // ignore FNC_1
      lookahead = findCType(value, start + 1);
    }
    if (lookahead == CType.TWO_DIGITS) { // at least two digits, start in code C
      return CODE_CODE_C;
    }
    return CODE_CODE_B;
  }

}
