EAN13.js

// Encoding documentation:
// https://en.wikipedia.org/wiki/International_Article_Number_(EAN)#Binary_encoding_of_data_digits_into_EAN-13_barcode

import EANencoder from './ean_encoder.js';
import Barcode from "../Barcode.js";

class EAN13 extends Barcode{
	constructor(data, options){
		// Add checksum if it does not exist
		if(data.search(/^[0-9]{12}$/) !== -1){
			data += checksum(data);
		}

		super(data, options);

		// Make sure the font is not bigger than the space between the guard bars
		if(!options.flat && 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;

		// Adds a last character to the end of the barcode
		this.lastChar = options.lastChar;
	}

	valid(){
		return this.data.search(/^[0-9]{13}$/) !== -1 &&
			this.data[12] == checksum(this.data);
	}

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

	// Define the EAN-13 structure
	getStructure(){
		return [
			"LLLLLL",
			"LLGLGG",
			"LLGGLG",
			"LLGGGL",
			"LGLLGG",
			"LGGLLG",
			"LGGGLL",
			"LGLGLG",
			"LGLGGL",
			"LGGLGL"
		];
	}

	// The "standard" way of printing EAN13 barcodes with guard bars
	guardedEncoding(){
		var encoder = new EANencoder();
		var result = [];

		var structure = this.getStructure()[this.data[0]];

		// Get the string to be encoded on the left side of the EAN code
		var leftSide = this.data.substr(1, 6);

		// Get the string to be encoded on the right side of the EAN code
		var rightSide = this.data.substr(7, 6);

		// Add the first digigt
		if(this.options.displayValue){
			result.push({
				data: "000000000000",
				text: this.text.substr(0, 1),
				options: {textAlign: "left", fontSize: this.fontSize}
			});
		}

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

		// Add the left side
		result.push({
			data: encoder.encode(leftSide, structure),
			text: this.text.substr(1, 6),
			options: {fontSize: this.fontSize}
		});

		// Add the middle bits
		result.push({
			data: "01010",
			options: {height: this.guardHeight}
		});

		// Add the right side
		result.push({
			data: encoder.encode(rightSide, "RRRRRR"),
			text: this.text.substr(7, 6),
			options: {fontSize: this.fontSize}
		});

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

		if(this.options.lastChar && this.options.displayValue){
			result.push({data: "00"});

			result.push({
				data: "00000",
				text: this.options.lastChar,
				options: {fontSize: this.fontSize}
			});
		}
		return result;
	}

	flatEncoding(){
		var encoder = new EANencoder();
		var result = "";

		var structure = this.getStructure()[this.data[0]];

		result += "101";
		result += encoder.encode(this.data.substr(1, 6), structure);
		result += "01010";
		result += encoder.encode(this.data.substr(7, 6), "RRRRRR");
		result += "101";

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

	static options() {
		return {
			flat: {
				type: "boolean",
				default: false,
			}
		};
	}
}

// Calulate the checksum digit
// https://en.wikipedia.org/wiki/International_Article_Number_(EAN)#Calculation_of_checksum_digit
function checksum(number){
	var result = 0;

	var i;
	for(i = 0; i < 12; i += 2){
		result += parseInt(number[i]);
	}
	for(i = 1; i < 12; i += 2){
		result += parseInt(number[i]) * 3;
	}

	return (10 - (result % 10)) % 10;
}

export default EAN13;