Implmented the EAN generation

ref #77

src/models/entities/RunnerCard.ts

@@ -6,6 +6,7 @@ import {
   IsOptional
 } from "class-validator";
 import { Column, Entity, ManyToOne, OneToMany, PrimaryGeneratedColumn } from "typeorm";
+import { RunnerCardIdOutOfRangeError } from '../../errors/RunnerCardErrors';
 import { ResponseRunnerCard } from '../responses/ResponseRunnerCard';
 import { Runner } from "./Runner";
 import { TrackScan } from "./TrackScan";
@@ -51,8 +52,27 @@ export class RunnerCard {
    * Generates a ean-13 compliant string for barcode generation.
    */
   public get code(): string {
-    //TODO: Implement the real deal
-    return '0000000000000'
+    const multiply = [1, 3];
+    let total = 0;
+    this.paddedId.split('').forEach((letter, index) => {
+      total += parseInt(letter, 10) * multiply[index % 2];
+    });
+    const checkSum = (Math.ceil(total / 10) * 10) - total;
+    return this.paddedId + checkSum.toString();
+  }
+
+  /**
+   * Returns this card's id as a string padded to the length of 12 characters with leading zeros.
+   */
+  private get paddedId(): string {
+    let id: string = this.id.toString();
+
+    if (id.length > 12) {
+      throw new RunnerCardIdOutOfRangeError();
+    }
+    while (id.length < 12) { id = '0' + id; }
+
+    return id;
   }
 
   /**