Goa

Goa is a very small, very simple MVCish framework for Node. I say
"MVCish" because it's built on top of Express
which already handles views. So it's more like an "MC" framework.
Except it doesn't do much with models, either. Whatever. It does
SOMETHING, I'm sure of it.


Installation

Install via NPM: npm install goa

$3

If you need legacy support for Express, you should use a version < 1.0.0 from NPM.
Source code is in the express3 branch.

Usage

Goa sits on top of Express. It's Express all the way down. Except for the top.
Which is Goa.

$3

Goa is a drop-in replacement for Express:
all Goa apps are Express apps.

As of v3.0.0, the interface to create an application changed from goa(...)
to goa.createApplication(...). Also, since v3.0.0 promises are supported in both
controller actions and controller factories.

As of v2.0.0, express is now a peer dependency which means you must supply
your own version of express to goa.

So, inside your sweet app, wherever you would normally initialize Express, do this
instead:

``javascript
const express = require('express');
const goa = require('goa');

const createController = (name, context, callback) => callback(null, {
index: (params, send) => send(goa.action('yay!'))
});

// or, using a promise
const createControllerViaPromise = async (name, context) => {
return await getMyController();
};

const app = goa.createApplication(createController, { express });
`

That will get your new Goa application up and running. Since it's just a normal
Express app, you can still configure() and use() and whatnot to your
heart's content (note that the express index is exposed on app.express):

`javascript
app.set('views', __dirname + '/views');
app.set('view engine', 'pug');
// etc.
`

$3

Routing is, literally, the same as Express. Because it delegates to the
default Express routing. So literally any route you were using in your
Express app you can use with Goa. Literally.

The only difference is that it does not use a route handler in the form
of function(req, res, next). Instead, in its place, you specify the
controller and action that you want to execute.

`javascript
//the "action" is optional, and defaults to "index" if not given
app.get('/awesome', { controller: 'foo', action: 'bar' });
`

$3

So you need a controller.

A controller factory is a function that creates controllers. It
takes three arguments:

1. the name of the controller to create (dictated from your route handler up there)
2. a context, which contains stuff that might be useful (specifically, the req and res)
3. a callback in the normal convention: callback(err, yourSweetController)

The properties on your controller correspond to actions. So if your
route handler looks like this: { controller: 'foo', action: 'bar' },
then your foo controller better look like this:

`javascript
{
bar: (params, send) => {
// do stuff
}
}
`

You can set up your controller factory however you want. Here's a sample one:

`javascript
const controllerFactory = (name, context, callback) => {
//"foo" => "FooController"
const className = name.charAt(0).toUpperCase() + name.substring(1) + 'Controller';

//assuming the file name is "controllers/FooController.js"
const Controller = require('./controllers/' + className);
callback(null, new Controller(context));
}
`

$3


Action methods are properties on controllers, like the "bar" thing we did up
above. They should always return some kind of Result object. There are seven
built-in Result objects:

1. ActionResult(content[, contentType, options]) - simply sends whatever content you give it
* goa.action('foo bar', 'text/plain');
2. JsonResult(json[, options]) - sends JSON
* goa.json({ foo: 'bar' });
3. FileResult(file[, options]) - sends a file (uses res.sendfile() and res.download())
* goa.file('/path/to/file');
* goa.file('/path/to/file', { maxAge: 60000 });
* goa.file('/path/to/file', { fileName: 'foo.txt' }); - sets Content-Disposition header
* goa.file('http://example.com/foo.txt'); - acts as reverse proxy
4. ViewResult(view[, params, options]) - renders a view with optional params
* goa.view('index.jade', { message: 'Welcome!' });
* goa.view('index.jade', { message: 'Welcome!' }, { contentType: 'text/xml' });
* goa.view('index.jade', function() { return { message: 'Welcome!' });
5. ErrorResult(error[, options = 500]) - delegates to Express's error handler
* goa.error(new Error('Verboten!'), 403);
6. RedirectResult(location[, options = 302]) - redirects to location
* goa.redirect('/foo');
7. EmptyResult([contentType]) - sends an empty response with status 204

All result objects should have an execute(res, next) function, if you decide to
implement your own.

Notice that each Result constructor has an options parameter. This can
be used for setting the status code of any of the results (it may be used
for additional things in the future). For all results except EmptyResult
you can simply pass a number for the status code, or an object { status: 404 }:
they are equivalent. EmptyResult always sets the status code to 204 No Content.

The preferred way of using the built-in result objects is via their factory
functions on the goa object, e.g. goa.view('myview'). But, if you like
typing, you can also access their constructors directly off of the
goa.results object: new goa.results.ViewResult('myview').

Action methods are passed a params object, which is a conglomeration of req.query,
req.body and req.params, in that order. That is, req.query.foo will be overridden
by req.body.foo, which will be overridden by req.params.foo.

If you need access to the raw request, you should make sure and inject
the context object into your controller and then you can do things like
var referrer = context.req.headers.referer; or something.

So your controller should do something like this:

`javascript
class MyController {
constructor(context, db) {
this.context = context;
this.db = db;
}

index(params, send) {
send(goa.view('index.pug', {
message: 'Welcome',
referrer: this.context.req.headers.referer
}));
}

save(params, send) {
const record = { content: params.content };
this.db.insert(record, (err, result) => {
if (err) {
send(goa.error(err));
return;
}

send(goa.redirect(/edit/${result.id}));
});
}

// also supports promises
async savePromise(params, send) {
try {
const result = await this.db.insert(record);
send(goa.redirect(/edit/${result.id}));
} catch (e) {
send(goa.error(e));
}
}
}
`

The same in TypeScript:
`typescript
import * as goa from 'goa';

interface SaveParams {
content: string;
}

class MyController {
private readonly context: goa.ControllerContext;
private readonly db: any;

public constructor(context: goa.ControllerContext, db: any) {
this.context = context;
this.db = db;
}

index(params: goa.ActionParams, send: goa.Send) {
send(goa.view('index.pug', {
message: 'Welcome',
referrer: this.context.req.headers.referer
}));
}

save(params: goa.ActionParams, send: goa.Send) {
const record: any = { content: params.content };
this.db.insert(record, (err, result) => {
if (err) {
send(goa.error(err));
return;
}

send(goa.redirect(/edit/${result.id}));
});
}

public async savePromise(params: goa.ActionParams, send: goa.Send) {
try {
const record: any = { content: params.content };
const result = await this.db.insert(record);
send(goa.redirect(/edit/${result.id}));
} catch (e) {
send(goa.error(e));
}
}
}
`

#### Unknown Actions
If an action is attempting to be executed, that doesn't exist on the controller, goa will
raise an error, which you can handle in your express error handler.

If you want more finegrained control over those errors, you can define a handleUnknownAction
method on your controller.

`javascript
{
handleUnknownAction: (params, send) => {
send(goa.view('errors/404', { message: 'That page does not exist' }, 404));
}
}
`

#### Hooking into rendering process
The send argument also accepts an onComplete callback:

`javascript
{
myAction: (params, send) => {
const renderStart = Date.now();
send(goa.view('some/view', { hello: 'world' }), (err) => {
if (err) {
console.error(rendering encountered an error: ${err.message});
}
const renderElapsed = Date.now() - renderStart;
console.log(rendering took ${renderElapsed}ms);
});
}
}
`

Note that any errors thrown from the onComplete callback will be ignored.

The onComplete callback can return a promise. Note that the promise will resolve
_before_ sending the response back to the client, so it's not recommended to perform
any heavy tasks inside the onComplete callback as it can hide slowness from the
normal program flow. Errors resulting from a rejected promise are ignored.

`javascript
{
myAction: (params, send) => {
const renderStart = Date.now();
send(goa.view('some/view', { hello: 'world' }), async (err) => {
const renderElapsed = Date.now() - renderStart;
await db.execute('INSERT INTO render_times (timestamp, elapsed) VALUES (?, ?)', Date.now(), renderElapsed);
});
}
}
`

$3

So, to set up your routes to use the controller above, you would do something like this:

`javascript
app.get('/', { controller: 'my' });
app.post('/save', { controller: 'my', action: 'save' });
`

As mentioned earlier, you can also use router parameters to define the
controller and action:

`javascript
// would handle requests like "/foo/bar" -> "foo" controller, "bar" action
app.get('/:controller/:action', {});

// "/post/edit/1" => "blog" controller, "edit" action; id would be in params.id
app.get('/post/:action/:id', { controller: 'blog' });
``