var allIn = require('then-all-in'),
    allSettledIn = require('then-all-settled-in'),
    emails = require('./emails');
 
app.patch('/account/:id', function(request, response, next) {
    var body = request.body;
 
    // Assume `emails.validateEmail()` is an asynchronous operation that
    // resolves to a Boolean, and `Account.get` constructs a promise for
    // an account model.
    var operations = allSettledIn({
        validation: emails.validateEmail(body.email),
        byId: Account.get(request.params.id)
    });
 
    operations.then(function(responses) {
        var changes = {},
            validation = responses.validation,
            byId = responses.byId;
 
        if (byId.state == 'rejected')
            throw byId.reason;
 
        var account = byId.value;
        if (validation.state == 'fulfilled' && validation.value === true && body.email != account.email) {
            // Assume `#setEmail()` is asynchronous.
            changes.email = account.setEmail(body.email);
        }
 
        if (body.phone != account.phone) {
            changes.phone = account.setPhone(body.phone);
        }
 
        return allIn(changes);
    }).done(function() {
        response.send(204);
    }, next);
});