zxing-js/library

/**
 * Set of CharsetEncoders for a given input string
 *
 * Invariants:
 * - The list contains only encoders from CharacterSetECI (list is shorter then the list of encoders available on
 *   the platform for which ECI values are defined).
 * - The list contains encoders at least one encoder for every character in the input.
 * - The first encoder in the list is always the ISO-8859-1 encoder even of no character in the input can be encoded
 *       by it.
 * - If the input contains a character that is not in ISO-8859-1 then the last two entries in the list will be the
 *   UTF-8 encoder and the UTF-16BE encoder.
 *
 * @author Alex Geller
 */

import { char } from '../../customTypings';
import Charset from '../util/Charset';
import StandardCharsets from '../util/StandardCharsets';
import StringEncoding from '../util/StringEncoding';
import StringUtils from './StringUtils';

class CharsetEncoder {
  public name: string;

  constructor(public readonly charset: Charset) {
    this.name = charset.name;
  }

  public canEncode(c: string): boolean {
    try {
      return StringEncoding.encode(c, this.charset) != null;
    } catch (ex) {
      return false;
    }
  }
}

export class ECIEncoderSet {
  private readonly ENCODERS: CharsetEncoder[] = [
    'IBM437',
    'ISO-8859-2',
    'ISO-8859-3',
    'ISO-8859-4',
    'ISO-8859-5',
    'ISO-8859-6',
    'ISO-8859-7',
    'ISO-8859-8',
    'ISO-8859-9',
    'ISO-8859-10',
    'ISO-8859-11',
    'ISO-8859-13',
    'ISO-8859-14',
    'ISO-8859-15',
    'ISO-8859-16',
    'windows-1250',
    'windows-1251',
    'windows-1252',
    'windows-1256',
    'Shift_JIS',
  ].map(name => new CharsetEncoder(Charset.forName(name)));
  private encoders: CharsetEncoder[] = [];
  private priorityEncoderIndex: number;

  /**
   * Constructs an encoder set
   *
   * @param stringToEncode the string that needs to be encoded
   * @param priorityCharset The preferred {@link Charset} or null.
   * @param fnc1 fnc1 denotes the character in the input that represents the FNC1 character or -1 for a non-GS1 bar
   * code. When specified, it is considered an error to pass it as argument to the methods canEncode() or encode().
   */
  constructor(stringToEncode: string, priorityCharset: Charset, fnc1: number) {
    const neededEncoders: CharsetEncoder[] = [];

    // we always need the ISO-8859-1 encoder. It is the default encoding
    neededEncoders.push(new CharsetEncoder(StandardCharsets.ISO_8859_1));
    let needUnicodeEncoder =
      priorityCharset != null && priorityCharset.name.startsWith('UTF');

    // Walk over the input string and see if all characters can be encoded with the list of encoders
    for (let i = 0; i < stringToEncode.length; i++) {
      let canEncode = false;
      for (const encoder of neededEncoders) {
        const singleCharacter = stringToEncode.charAt(i);
        const c = singleCharacter.charCodeAt(0);

        if (c === fnc1 || encoder.canEncode(singleCharacter)) {
          canEncode = true;
          break;
        }
      }

      if (!canEncode) {
        // for the character at position i we don't yet have an encoder in the list
        for (const encoder of this.ENCODERS) {
          if (encoder.canEncode(stringToEncode.charAt(i))) {
            // Good, we found an encoder that can encode the character. We add him to the list and continue scanning
            // the input
            neededEncoders.push(encoder);
            canEncode = true;
            break;
          }
        }
      }

      if (!canEncode) {
        // The character is not encodeable by any of the single byte encoders so we remember that we will need a
        // Unicode encoder.
        needUnicodeEncoder = true;
      }
    }

    if (neededEncoders.length === 1 && !needUnicodeEncoder) {
      // the entire input can be encoded by the ISO-8859-1 encoder
      this.encoders = [neededEncoders[0]];
    } else {
      // we need more than one single byte encoder or we need a Unicode encoder.
      // In this case we append a UTF-8 and UTF-16 encoder to the list
      this.encoders = [];
      let index = 0;
      for (const encoder of neededEncoders) {
        this.encoders[index++] = encoder;
      }

      // this.encoders[index] = new CharsetEncoder(StandardCharsets.UTF_8);
      // this.encoders[index + 1] = new CharsetEncoder(StandardCharsets.UTF_16BE);
    }

    // Compute priorityEncoderIndex by looking up priorityCharset in encoders
    let priorityEncoderIndexValue = -1;
    if (priorityCharset != null) {
      for (let i = 0; i < this.encoders.length; i++) {
        if (
          this.encoders[i] != null &&
          priorityCharset.name === this.encoders[i].name
        ) {
          priorityEncoderIndexValue = i;
          break;
        }
      }
    }
    this.priorityEncoderIndex = priorityEncoderIndexValue;

    // invariants
    // if(this?.encoders?.[0].name !== StandardCharsets.ISO_8859_1)){
    // throw new Error("ISO-8859-1 must be the first encoder");
    // }
  }

  public length(): number {
    return this.encoders.length;
  }

  public getCharsetName(index: number): string {
    if (!(index < this.length())) {
      throw new Error('index must be less than length');
    }
    return this.encoders[index].name;
  }

  public getCharset(index: number): Charset {
    if (!(index < this.length())) {
      throw new Error('index must be less than length');
    }
    return this.encoders[index].charset;
  }

  public getECIValue(encoderIndex: number): number {
    return this.encoders[encoderIndex].charset.getValueIdentifier();
  }

  /*
   *  returns -1 if no priority charset was defined
   */
  public getPriorityEncoderIndex(): number {
    return this.priorityEncoderIndex;
  }

  public canEncode(c: char, encoderIndex: number): boolean {
    if (!(encoderIndex < this.length())) {
      throw new Error('index must be less than length');
    }
    return true;
  }

  public encode(c: char, encoderIndex: number): Uint8Array {
    if (!(encoderIndex < this.length())) {
      throw new Error('index must be less than length');
    }

    return StringEncoding.encode(
      StringUtils.getCharAt(c),
      this.encoders[encoderIndex].name
    );
  }
}