especificos-web-V2/back/components/middlewares/response.js

var R = require('ramda');
var LANGS = [ 'ES', 'EN' ];
var DEFAULT_LANG = 'ES';

function selectLang(lang) {
    return function(x) {
        if(R.is(String, x)) {
            return x;
        } else {
            if (R.isNil(R.prop(lang, x))) {
                return x;
            } else {
                var x_ = x.toObject();
                x_ = R.merge(x_, R.prop(lang, x_));
                return R.omit(LANGS, x_);
            }
        }
    }
}

module.exports = function (fn) {
    return function (req, res, next) {
        var projection = req.headers.lang ? req.headers.lang : DEFAULT_LANG;

        return fn(req, res, next).then(function (xs) {

            var result = R.is(Array, xs) ? xs.map(selectLang(projection)) : selectLang(projection)(xs);
            res.json(result);
        }, function (error) {
            console.error('API: ', error)
            res.status(500).json({error: error});
        })
    } 
}