cnf-barcode/src/lib/barcodes/EAN_UPC/UPCE.js

a barcode generator

// Encoding documentation:
// https://en.wikipedia.org/wiki/Universal_Product_Code#Encoding
//
// UPC-E documentation:
// https://en.wikipedia.org/wiki/Universal_Product_Code#UPC-E

import encode from './encoder';
import Barcode from "../Barcode.js";
import { checksum } from './UPC.js';

const EXPANSIONS = [
  "XX00000XXX",
  "XX10000XXX",
  "XX20000XXX",
  "XXX00000XX",
  "XXXX00000X",
  "XXXXX00005",
  "XXXXX00006",
  "XXXXX00007",
  "XXXXX00008",
  "XXXXX00009",
];

const PARITIES = [
  ["EEEOOO", "OOOEEE"],
  ["EEOEOO", "OOEOEE"],
  ["EEOOEO", "OOEEOE"],
  ["EEOOOE", "OOEEEO"],
  ["EOEEOO", "OEOOEE"],
  ["EOOEEO", "OEEOOE"],
  ["EOOOEE", "OEEEOO"],
  ["EOEOEO", "OEOEOE"],
  ["EOEOOE", "OEOEEO"],
  ["EOOEOE", "OEEOEO"],
];

class UPCE extends Barcode {
  constructor(data, options) {
    // Code may be 6 or 8 digits;
    // A 7 digit code is ambiguous as to whether the extra digit
    // is a UPC-A check or number system digit.
    super(data, options);
    this.isValid = false;
    if (data.search(/^[0-9]{6}$/) !== -1) {
      this.middleDigits = data;
      this.upcA = expandToUPCA(data, "0");
      this.text = options.text
				|| `${this.upcA[0]}${data}${this.upcA[this.upcA.length - 1]}`;
      this.isValid = true;
    } else if (data.search(/^[01][0-9]{7}$/) !== -1) {
      this.middleDigits = data.substring(1, data.length - 1);
      this.upcA = expandToUPCA(this.middleDigits, data[0]);

      if (this.upcA[this.upcA.length - 1] === data[data.length - 1]) {
        this.isValid = true;
      } else {
        // checksum mismatch
        return;
      }
    } else {
      return;
    }

    this.displayValue = options.displayValue;

    // Make sure the font is not bigger than the space between the guard bars
    if (options.fontSize > options.width * 10) {
      this.fontSize = options.width * 10;
    } else {
      this.fontSize = options.fontSize;
    }

    // Make the guard bars go down half the way of the text
    this.guardHeight = options.height + this.fontSize / 2 + options.textMargin;
  }

  valid() {
    return this.isValid;
  }

  encode() {
    if (this.options.flat) {
      return this.flatEncoding();
    }

    return this.guardedEncoding();
  }

  flatEncoding() {
    let result = "";

    result += "101";
    result += this.encodeMiddleDigits();
    result += "010101";

    return {
      data: result,
      text: this.text,
    };
  }

  guardedEncoding() {
    const result = [];

    // Add the UPC-A number system digit beneath the quiet zone
    if (this.displayValue) {
      result.push({
        data: "00000000",
        text: this.text[0],
        options: { textAlign: "left", fontSize: this.fontSize },
      });
    }

    // Add the guard bars
    result.push({
      data: "101",
      options: { height: this.guardHeight },
    });

    // Add the 6 UPC-E digits
    result.push({
      data: this.encodeMiddleDigits(),
      text: this.text.substring(1, 7),
      options: { fontSize: this.fontSize },
    });

    // Add the end bits
    result.push({
      data: "010101",
      options: { height: this.guardHeight },
    });

    // Add the UPC-A check digit beneath the quiet zone
    if (this.displayValue) {
      result.push({
        data: "00000000",
        text: this.text[7],
        options: { textAlign: "right", fontSize: this.fontSize },
      });
    }

    return result;
  }

  encodeMiddleDigits() {
    const numberSystem = this.upcA[0];
    const checkDigit = this.upcA[this.upcA.length - 1];
    const parity = PARITIES[parseInt(checkDigit)][parseInt(numberSystem)];
    return encode(this.middleDigits, parity);
  }
}

function expandToUPCA(middleDigits, numberSystem) {
  const lastUpcE = parseInt(middleDigits[middleDigits.length - 1]);
  const expansion = EXPANSIONS[lastUpcE];

  let result = "";
  let digitIndex = 0;
  for (let i = 0; i < expansion.length; i++) {
    const c = expansion[i];
    if (c === 'X') {
      result += middleDigits[digitIndex++];
    } else {
      result += c;
    }
  }

  result = `${numberSystem}${result}`;
  return `${result}${checksum(result)}`;
}

export default UPCE;