PetitTetonMeteor/imports/api/Barcode.js

import {Mongo} from "meteor/mongo";
import { Meteor } from 'meteor/meteor';
import { check } from 'meteor/check';
import 'meteor/aldeed:collection2/static'
import SimpleSchema from 'meteor/aldeed:simple-schema';
import Products from "./Product";
import Measures from "./Measure";

let Barcodes = new Mongo.Collection('Barcodes');

if(Meteor.isServer) {
	//Set MongoDB indexes (or remove them) here.
	try {
		Barcodes.rawCollection().createIndex({barcodeId: -1}, {unique: true})
		Barcodes.rawCollection().createIndex({productAndMeasureId: -1}, {unique: true})
	} catch(e) {console.log("Caught exception while setting indexes in MongoDB"); console.error(e)}
}

// A simple mapping between a concatenation of the product & measure ID and a unique sequential number for the barcode.  This allows us to have a small number to keep our barcodes simple, while maintaining the more traditional MongoDB ID's for the Product and Measure.
const BarcodesSchema = new SimpleSchema({
	barcodeId: {
		type: Number,
		label: "Barcode ID",
		optional: false,
		//index: 1,
		//unique: true
	},
	productAndMeasureId: {  //Just the two ids jammed together with a single space between them.
		type: String,
		label: "Product And Measure ID",
		optional: false,
		//index: 1,
		//unique: true
	}
});

if(Meteor.isServer) {
	//Meteor.publish('barcodes', function() {
	//	return Barcodes.find({});
	//});
	
	Meteor.methods({
		getBarcodeId: async function(productId, measureId) {
			check(productId, String);
			check(measureId, String);
			
			let hasProduct = await Meteor.collections.Products.findOneAsync({_id: productId}, {fields: {}});
			let hasMeasure = await Meteor.collections.Measures.findOneAsync({_id: measureId}, {fields: {}});
			
			if(hasProduct && hasMeasure) {
				let existing = await Barcodes.findOneAsync({productAndMeasureId: productId + ' ' + measureId});
				
				if(existing) {
					return existing.barcodeId;
				}
				else {
					let c = 0;
					
					//Try a thousand times before failing.  Should never fail, should also not ever need to try a thousand times (unless we somehow automate label generation to the point where a 1000 processes at once are requesting labels that have never been generated before - highly unlikely).
					while(c++ < 1000) {
						//Lookup the most likely next barcode id from the db, then attempt to insert with it.  If it fails due to duplication, then increment and repeat.
						//let cursor = Products.find({}, {barcodeId: 1}).sort({barcodeId: -1}).limit(1);  //Since currently products are never removed, we shouldn't need to detect sequence gaps and fill them in (odds are we will never use more than 10k numbers anyway).
						//let barcodeId = cursor.hasNext() ? cursor.next().barcodeId + 1 : 1;
						let product = await Products.findOneAsync({barcodeId: {$exists: true}}, {sort: {barcodeId: -1}})
						let barcodeId = product ? product.barcodeId : 1;
						
						await Barcodes.insertAsync({productAndMeasureId: productId + ' ' + measureId, barcodeId}, function(err, id) {
							if(err) console.log(err);
							else return barcodeId;
						});
					}
					
					//If we are still here, then there was a massive failure (c exceeded 1000).
					console.log("We failed to generate a new barcode ID 1000 times, so we are giving up.  This should never happen.");
					throw new Meteor.Error(403, "Unable to generate a barcode ID.");
				}
			}
			else {
				//Cannot find either the product or the measure in the db.  Cannot give an id.
				console.log("Unable to generate a barcode ID because we could not find the product " + productId + " OR we could not find the measure " + measureId);
				throw new Meteor.Error(403, "Unable to find the product or the measure.  Both must exist in order to generate a barcode ID.");
			}
		},
	});
}

//Allows the client to do DB interaction without calling server side methods, while still retaining control over whether the user can make changes.
Barcodes.allow({
	insert: function() {return false;},
	update: function() {return false;},
	remove: function() {return false;}
});

export default Barcodes;