Declarative Backend

gen.config.js

export default {
  'users': 'User'
}

middleware.js

'use strict';

import compose from 'koa-compose';
import convert from 'koa-convert';
import logger from 'koa-logger';
import cors from 'koa-cors';
import bodyParser from 'koa-bodyparser';
//import session from 'koa-generic-session';

export default function middleware() {
  return compose([
    logger(),
    convert(cors()),
    convert(bodyParser()),
//    convert(session()),
  ]);
}

export const create = (model) =>
  (ctx, next) => (ctx.state[model.name] = new model()) && next();

export const save = (model) => {
  return async (ctx, next) =>  {
    const interest = Object.assign(ctx.state[model.name], ctx.request.body);
    await interest.save();
    await next();
  }
}

export const findOne = (config) => (model) => {
  return async (ctx, next) => {
    const optional = (name) => ctx.params[name] || ctx.request.body[name];

    const interest = ctx.state[model.name] = await model.findOne({
      [config.name]: optional(config.name)
    });

    if (!config.throwFound ^ !!interest) {
       ctx.throw(config.throwCode || 404);
    }

    await next();
  }
}

export const findById = findOne({ name: '_id' });

export const index = ({route, model}) => (async (ctx) => {
  ctx.body = await model.find({});
});

export const response = ({route, model}) => (async (ctx) => {
  ctx.body = ctx.state.model;
});

routes_index.js

import mongoose from 'mongoose';
import routes from './gen.config';
import {
  index,
  findOne,
  findById,
  create,
  save,
  response
} from '../../middleware';

const generateRoutes = (router, params) => {
  console.log(`generate route for /${params.route}`);
  router
    // GET /api/{route.name} - Get item list
    .get(`/${params.route}`,
      index(params))

    // GET /api/{route.name}/:itemId - Get item
    .get(`/${params.route}/:_id`,
      findById(params.model),
      response(params))

    // POST /api/{route.name} - Create item
    .post(`/${params.route}`,
      create(params.model),
      save(params.model),
      response(params))

    // PUT /api/{route.name}/:itemId - Update item
    .put(`/${params.route}/:_id`,
      findById(params.model),
      save(params.model),
      response(params)
    )
  ;
}

export default (router) => Object.keys(routes).reduce(
  (prev, key) => {
    const params = routes[key];
    let { model, auth } = params;
    model = model || params;

    return generateRoutes(router, {
      route: key,
      model: mongoose.model(model),
      auth
    })
  }, {}
);