Combo Handler
=============


This is a simple combo handler for Node.js, usable either as [Connect][]
middleware or as an [Express][] server. It works just like the combo handler
service on the Yahoo! CDN, which you'll be familiar with if you've used YUI.

The combo handler is compatible with the [YUI][] Loader, so you can use it to
host YUI, or you can use it with any other JavaScript or CSS if you're willing
to construct the combo URLs yourself.

The combo handler itself doesn't perform any caching or compression, but stick
[Nginx][] or something in front of it and you should be ready to rock in
production.

[Connect]: https://github.com/senchalabs/connect
[Express]: https://github.com/visionmedia/express
[Nginx]: http://nginx.org/
[YUI]: http://yuilibrary.com/

Installation
------------

Install using npm:

``bash
npm install combohandler
`

Or just clone the GitHub repo:

`bash
git clone git://github.com/rgrove/combohandler.git
`


Usage
-----

The combohandler module provides a configurable Connect middleware that can be
used to add combo handling capability to any Connect-based request handler (like
Express).

The combohandler/lib/server module creates a standalone Express server instance,
or augments an existing server, to perform combo handling for a set of
configurable routes.




$3

The combo handler middleware can be used as application-wide middleware for all
routes:

`js
var combo = require('combohandler');
app.use(combo.combine({rootPath: '/local/path/to/files'}));
`

Or as route middleware for a specific route:

`js
app.get('/foo', combo.combine({rootPath: '/local/path/to/foo'}), combo.respond);
`

In either case, the middleware will perform combo handling for files under the
specified local rootPath when requested using a URL with one or more file paths
in the query string:

`text
http://example.com/?[&path][...]
`

For example:

`text
http://example.com/foo?file1.js
http://example.com/foo?file1.js&file2.js
http://example.com/foo?file1.js&file2.js&subdir/file3.js
`

Attempts to traverse above the rootPath or to request a file that doesn't
exist will result in a BadRequest error being bubbled up.

Here's a basic Express app that uses the combo handler as route middleware for
multiple routes with different root paths:

`js
var combo = require('combohandler'),
express = require('express'),

app = express();

app.configure(function () {
app.use(express.errorHandler());
});

// Return a 400 response if the combo handler generates a BadRequest error.
app.use(combo.errorHandler());

// Given a root path that points to a YUI 3 root folder, this route will
// handle URLs like:
//
// http://example.com/yui3?build/yui/yui-min.js&build/loader/loader-min.js
//
app.get('/yui3', combo.combine({rootPath: '/local/path/to/yui3'}), combo.respond);

app.listen(3000);
`

#### combo.respond

The respond method exported by require('combohandler') is a convenience
method intended to be the last callback passed to an
express route.
Unless you have a very good reason to avoid it, you should probably use it.
Here is the equivalent callback:

`js
function respond(req, res) {
res.send(res.body);
}
`

This method may be extended in the future to do fancy things with optional
combohandler middleware.

#### combo.errorHandler

The errorHandler export encapsulates the convention of sending BadRequest
errors with an optional errorMaxAge config.
By default, BadRequest errors are served with a 5 minute max-age header.

To explicitly disable caching (via
Pragma: no-cache and
Cache-Control: private,no-store
headers), pass null in the options object:

`js
app.use(combo.errorHandler({
errorMaxAge: null
}));
`

Any other value (including zero) for errorMaxAge is interpreted as the
desired duration in seconds.

$3

If you just want to get a server up and running quickly by specifying a mapping
of routes to local root paths, use the combohandler/lib/server module.
It creates a barebones Express server that will perform combo handling on the
routes you specify:

`js
var comboServer = require('combohandler/lib/server'),
app;

app = comboServer({
roots: {
'/yui3': '/local/path/to/yui3'
}
});

app.listen(3000);
`

$3

If you already have an existing Express server instance and just want to add
some combo handled routes to it easily, you can augment your existing server
with combo handled routes:

`js
var comboServer = require('combohandler/lib/server');

comboServer({
roots: {
'/yui3': '/local/path/to/yui3'
}
}, myApp); // Assuming myApp is a pre-existing Express server instance.
`

$3

If installed globally via npm -g install,
the CLI executable combohandler is provided.
If you're operating from a local clone,
npm link in the repository root and you're off to the races.
To start the default single-process server,
it's as simple as

`bash
combohandler


combohandler now running until you hit Ctrl+C


`

Of course, the default output leaves something to be desired: that is to say,
any output.

#### Root Configuration

At the very least,
you need to provide some route-to-rootPath mappings for your CLI combohandler.

When passed in the --rootsFile option,
the JSON file contents should follow this pattern:

`json
{
"/yui3": "/local/path/to/yui3"
}
`

When passed as individual --root parameters,
the equivalent to the JSON above looks like this:

`bash
combohandler --root /yui3:/local/path/to/yui3 [...]
`

To run the standalone server in production mode, set the NODE_ENV variable to
production before running it:

`bash
NODE_ENV=production combohandler --root /yui3:/path/to/yui3
`

#### CLI Usage

`text
Usage: combohandler [options]

General Options:
-h, --help Output this text
-v, --version Prints combohandler's version

Combine Options:
-p, --port Port to listen on. [8000]
-a, --server Script that exports an Express app [combohandler/lib/server]
-r, --root String matching the pattern '{route}:{rootPath}'.
You may pass any number of unique --root configs.
-f, --rootsFile Path to JSON routes config, exclusive of --root.
-b, --basePath URL path to prepend when rewriting relative url()s. ['']
-w, --webRoot Filesystem path to base rewritten relative url()s from. ['']
Use this instead of --basePath when using route parameters.
Overrides behaviour of --basePath.
-m, --maxAge 'Cache-Control' and 'Expires' value, in seconds. [31536000]
Set this to 0 to expire immediately, null to omit these
headers entirely.

Cluster Options:
--cluster Enable clustering of server across multiple processes.
-d, --pids Directory where pidfiles are stored. [$PREFIX/var/run]
-n, --workers Number of worker processes. [os.cpus.length, max 8]
-t, --timeout Timeout (in ms) for process startup/shutdown. [5000]

--restart Restart a running master's worker processes. (SIGUSR2)
--shutdown Shutdown gracefully, allows connections to close. (SIGTERM)
--status Logs status of master and workers.
--stop Stop server abruptly, not waiting for connections. (SIGKILL)
`

The --port and --server options may also be set via npm package config settings:

`bash
npm -g config set combohandler:port 2702
npm -g config set combohandler:server /path/to/server.js
`

Unlike the --server option, a path specified in this manner must be absolute.

$3

With the advent of node v0.8.x, the core cluster module is now usable,
and combohandler now regains the capability it once had.
Huzzah! said the villagers.

To run a clustered combohandler from the CLI, just add the --cluster flag:

`bash
combohandler --cluster --root /yui3:/path/to/yui3
`

To clusterize combohandler from a module dependency,
combohandler/lib/cluster is your friend:

`js
var comboCluster = require('combohandler/lib/cluster');
var app = comboCluster({
pids: '/path/to/piddir',
server: './myserver.js',
roots: {
'/yui3': '/local/path/to/yui3'
}
});
app.listen(2702);
`

Optional Middleware
-------------------

$3

Because the combo handler changes the path from which CSS files are loaded,
relative URLs in CSS files need to be updated to be relative to the
combohandled path.
Set the basePath or webRoot configuration option to have the
combohandler default middleware do this automatically.

`js
// This static route can be used to load images and other assets that shouldn't
// be combined.
//
app.use('/public', express.static(__dirname + '/public'));

// This route will combine requests for files in the public directory, and will
// also automatically rewrite relative paths in CSS files to point to the
// non-combohandled static route defined above.
//
app.get('/combo', combo.combine({
rootPath: __dirname + '/public',
basePath: '/public'
}), combo.respond);

// The equivalent config as the previous route, except using webRoot
app.get('/combo', combo.combine({
rootPath: __dirname + '/public',
webRoot : __dirname
}), combo.respond);
`

Alternatively, you can use the built-in cssUrls middleware as a separate
route callback. cssUrls must always be placed after the default combine
middleware when used in this fashion.

`js
// This route provides the same behaviour as the previous example, providing
// better separation of concerns and the possibility of inserting custom
// middleware between the built-in steps.
app.get('/combo',
combo.combine({
rootPath: __dirname + '/public'
}),
combo.cssUrls({
basePath: '/public'
}),
combo.respond);
`

Finally, the cssUrls middleware has the ability (disabled by default) to
rewrite @import paths in the same manner as url() values. As @import is
considered an anti-pattern in production code, this functionality is strictly
opt-in and requires passing true as the rewriteImports property in the
middleware options object.

`js
// Automagically
app.get('/combo', combo.combine({
rootPath: __dirname + '/public',
webRoot : __dirname,
rewriteImports: true
}), combo.respond);

// As explicit middleware
app.get('/combo',
combo.combine({ rootPath: __dirname + '/public' }),
combo.cssUrls({ basePath: '/public', rewriteImports: true }),
combo.respond);
`

#### basePath or webRoot?

In the simplest case,
basePath and webRoot reach the same result from different directions.
basePath allows you to rewrite a single well-known path under any root,
whereas webRoot will handle any number of paths under a well-known root.

In general, if you are using both optional middleware,
you should prefer webRoot over basePath.

$3

To enable resolution of dynamic subtree paths under a given rootPath,
simply add a route parameter
to both the route and the rootPath config.

`js
app.get('/combo/yui/:version', combo.combine({
rootPath: '/local/path/to/yui/:version/build'
}), combo.respond);
`

Given this config,
any YUI release tarball you explode
into a versioned subdirectory of /local/path/to/yui/ would be available
under a much shorter URL than the default config provides:

`text
http://example.com/combo/yui/3.9.1?yui/yui-min.js&yui-throttle/yui-throttle-min.js
// vs
http://example.com/combo/yui?3.9.1/build/yui/yui-min.js&3.9.1/build/yui-throttle/yui-throttle-min.js
`

If the built-in dynamicPath middleware is used manually, it _must_ be
inserted before the default combine middleware.


Using as a YUI 3 combo handler
------------------------------

With a tiny bit of configuration, you can tell YUI to use your custom combo
handler instead of the Yahoo! combo handler. Here's an example:

`html


``

License
-------

Copyright (c) 2012 Yahoo! Inc. All rights reserved.

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.