example.js

const mockData = { message: 'Welcome!' };

const controllers = {
  createOne(model, body) {
    return Promise.resolve(mockData);
  },
  updateOne(documentToUpdate, update) {
    return Promise.resolve(mockData);
  },
  deleteOne(documentToDelete) {
    return Promise.resolve(mockData);
  },
  getOne(documentToGet) {
    return Promise.resolve(mockData);
  },
  getAll(model) {
    return Promise.resolve(mockData);
  },
  findByParam(model, id) {
    return Promise.resolve(mockData);
  },
};

const createOne = model => (req, res, next) => controllers.createOne(model, req.body)
  .then(result => res.json(result))
  .catch(e => next(e));

// PUT /user/:id req will be in form: { name: updatedName }

const updateOne = model => async (req, res, next) => {
  const docToUpdate = req.docFromId;
  const update = req.body;

  return controllers.updateOne(docToUpdate, update)
    .then(doc => res.json(doc))
    .catch(e => next(e));
};

const deleteOne = model => (req, res, next) => controllers.deleteOne(req.docFromId)
  .then(doc => res.json(doc))
  .catch(e => next(e));

const getOne = model => (req, res, next) => controllers.getOne(req.docToUpdate)
  .then(doc => res.json(doc))
  .catch(e => next(e));

const getAll = model => (req, res, next) => controllers.getAll(model)
  .then(docs => res.json(docs))
  .catch(e => next(e));

const findByParam = model => (req, res, next, id) => controllers.findByParam(model, id)
  .then((doc) => {
    if (!doc) {
      next(new Error('Not Found Error'));
    } else {
      req.docFromId = doc;
      next();
    }
  });

const generateController = function generateController(model, overrides = {}) {
  const defaults = {
    findByParam: findByParam(model),
    getAll: getAll(model),
    getOne: getOne(model),
    deleteOne: deleteOne(model),
    updateOne: updateOne(model),
    createOne: createOne(model),
  };

  return { ...defaults, ...overrides };
};

module.exports = {
  generateController,
  controllers,
};