Simple Koa 2 middleware that transparently exposes Waterline (node 7.6+)

koa-simple-waterline.js

'use strict';

const Waterline = require('waterline');
let _waterline;

const upper = (str) => str[0].toUpperCase() + str.slice(1);
const isInvalid = (model) => (!model.identity);

const init = async ({ models, adapters, connections }) => {
    if (_waterline) return Promise.resolve(_waterline);

    _waterline = new Waterline();
    models.forEach((model) => {
        if (isInvalid(model)) return;

        let collection = Waterline.Collection.extend(model);
        _waterline.loadCollection(collection);
    });

    return new Promise((resolve, reject) => {
        _waterline.initialize({ adapters, connections }, (err, _) => {
            if (err) reject(err);
                
            resolve(_waterline);
        });
    });
};

module.exports = (config) => {
    return async (ctx, next) => {
        if (!ctx.waterline) {
            const waterline = await init(config);
            ctx.waterline = waterline;
        }
        await next();
    }
};