routes.js

var router = require(/* definir un nombre unico */ 'koa-router'),
    mongoose = require('mongoose'),
    User = mongoose.model('User'),
    Report = mongoose.model('Report'),
    // home seria el router que parte desde el url '/'
    home = router(),
    users = home.route('/users'),
    reports = home.route(
        // no se si sea buena idea incluir el '/' al comienzo del regex
        /\/(reports|users\/:user\/reports)/
    ),
    report = reports.route('/')
    user = users.route('/:user');
    
users.get('/', function* (next) {
    this.response.body = yield User.find();
});

user.get('/', function* (next) {
    this.response.body = this.user;
});

user.put('/', function* (next) {
    this.user.eachPath((path) => {
        var val = this.request.body[path]
        this.user.set(path, val);
    });
});
    
home.param('user', function* (next, value) {
    this.user = yield User.findById(value);
    if (!this.user) yield new Error('UserNotFound');
    yield next;
    if (this.user.isModified()) {
        yield this.user.save();
    }
});

reports.param('report', function* (next, value) {
    this.report = yield Report.findById(value);
    if (!this.report) yield new Error('ReportNotFound');
    yield next;
    if (this.report.isModified()) {
        yield this.report.save();
    }
});

module.exports = home;