express-bolongese.js

const express = require('express');
const Promise = require('bluebird');
const app = express();

const logger = console.log;
const tracking = console.log;
const exceptionCatcher = console.error;

const getDataById = () => new Promise((resolve, reject) => {
    resolve({data: 'I am response'});
});

const dataFilterService = () => new Promise((resolve, reject) => {
    resolve({data: 'I am filtered'});
});;

app.param('entry_id', (req, res, next, entry_id) => {    
    getDataById(entry_id)
        .then((data) => {
            req.metadata = {
                info: 'data is received',
                event: 'data.received'
            };
            
            req.result = data;

            next();
        })
        .catch(next);
});


app.get('/data/:entry_id', (req, res, next) => {
    next();
});


app.get('/data/:entry_id/filtered', (req, res, next) => {    
    dataFilterService(req.result)
        .then((apiResult) => {
            req.metadata = {
                info: 'data is filtered',
                event: 'api.result.received'
            }
            
            req.result = apiResult;
            next();
        })
        .catch(next);
});

app.use((req, res, next) => {
    if (req.metadata.event) {
        tracking(req.metadata.event);
        next();
    }
});

app.use('/data', (req, res, next) => {
    if (req.metadata.info) {
        logger(req.metadata.info);
        next();
    }
});

app.use((req, res, next) => {
    if (req.result) {
        res.json(req.result);
    } else {
        next(new Error('Result not found'));
    }
});

app.use((err, req, res, next) => {
    logger('[ERROR] ', err.message);
    exceptionCatcher(err);
    res.status(500).json({
        error: 'Something went wrong'
    });
});

app.listen(3000);