reverse !build status

A [DSL][domain-specific-language] for building routers. Supports forward and
reverse matching.

``javascript
const routes = require('reverse')

const slug = routes.param('slug', /^[\w-]+$/)
const myRouter = routes
GET /blog/${slug} showPost
POST /blog/${slug} updatePost
PUT /blog/${slug} replacePost
GET / listPosts
({
showPost () {
}
listPosts () {
}
updatePost () {
}
replacePost () {
}
})

myRouter.match('GET', '/blog/hello-world')
// Match { name: 'showPost', controller: ..., }

myRouter.reverse('showPost', {
'slug': 'hello'
}) // "/blog/hello"
`

Documentation

* [Why reverse?][docs-why-reverse]
* [Getting started][docs-getting-started]
* [Topics][docs-topics]
* [Defining Targets][docs-defining-targets]
* [Validating Parameters][docs-validating-params]
* [Binding Controllers][docs-binding-controllers]
* [Nesting Routers][docs-nesting-routers]
* [Using Match Objects][docs-using-match-objects]
* [Using reverse][docs-using-reverse]
* [API reference][docs-api-reference]
* Router
* Language
* Controllers
* Router#match
* Match
* Router#reverse
* Parameter

API

#### reverse ̀ ̀ → Function(Controller) → Router

Use reverse as a template literal tag against a string containing Language
to create a function. That function can bind routes to a controller to create a
Router instance. The function may be used with multiple controllers to create
multiple Router instances.

Example:

`javascript
const reverse = require('reverse')
const slug = reverse.param('slug', /^[\w\-]+$/)

const createCRUDRouter = reverse
GET /${slug} show
DELETE /${slug} delete

const blogRouter = createCRUDRouter({
show: showBlog,
delete: deleteBlog
})

const commentRouter = createCRUDRouter({
show: showComment,
delete: deleteComment
})

const rootURLs = reverse
* /blog blog
* /blog/${slug}/comments comments
({
blog: blogRouter,
comments: commentRouter
})
`

Each line containing $method $route $name is known as a target. Note that
the createCRUDRouter function is invoked twice on different object literals.
These object literals are controllers, and the invocation creates
routers. Routers may include other routers, as we've done here with
rootURLs (e.g., one target is blog, which in the controller object
points to blogRouter.)

This creates two routes functions that produce three Router instances.
The net result is that both "blogs" and "comments" are linked to a root
router. Targets not matched by an "included" router will fall through to
the parent router.

##### Language

The language is a template literal string, each line of which is comprised
of the following parts:

$METHOD $ROUTE $NAME

Each line with these elements defines a target. All whitespace between any
of these parts is ignored.

$METHOD defines the HTTP methods that the target accepts. Valid values are all http methods [recognized by Node][node-methods], and (for "match all".) Only strings may be interpolated here. All other interpolations are disallowed.
* $ROUTE defines the route that must be matched. Interpolated objects must be
valid parameters. It's common to begin the route with a leading /.
* $NAME is a string that will be used to match a property in bound controllers. Only string interpolation is allowed here, all others are disallowed.

The # character will be interpeted as the beginning of a line comment and may
appear anywhere in the text.

##### Controller object

A controller, as aforementioned, is any object passed to the function returned
from reverse ̀ ̀. There should be a key for every target $NAME
defined in the string passed as Language.

`javascript
const createCRUDRouter = reverse
GET /${slug} show
DELETE /${slug} delete

// OK:
createCRUDRouter({
show: function () { },
delete() { }
})

// also OK:
class NetBeans {
show () {
}
delete () {
}
}
createCRUDRouter(new NetBeans())
`

-------------

##### Router#match(method:String, route:String) → Match | null

Given an HTTP method and a string representing the [pathname of the url][url-parse],
return a Match object (or null, if no target matches.)

##### Router#concat(rhs:Router) → Router

Concatenate two existing routers together, returning a new Router that nests
the two input routers.

###### Match object

A Match object contains the following properties:

* controller — the controller object.
* name — the name of the target.
* context — a Map containing processed parameters.
* next — If the matched target was included in another router, this will
point to the parent target. Otherwise, it will point to null.

To get the full list of matches:

`
// using rootURLs from above:
const match = rootURLs.match('GET', '/blog/hello-world/comments/hi')
for (var submatch of match) {
console.log(submatch.context) // Map { slug => hi }, Map { slug => hello-world }
}
`

##### Router#reverse(name:String[, args:Object]) → String | null

Given a dot-delimited string of names and an optional "args" object containing
values to insert for parameters, return a string representing any targets that
match.

This is useful so that objects can refer to routes without knowing specifics
of the full url. An example:

`javascript
class Comment {
constructor (blogPost, slug, content) {
this.blogPost = blogPost
this.slug = slug
this.content = content
}
get url() {
// fill in the parameters using the knowledge
// this comment object has:
return rootURLs.reverse('comments.show', {
'comments.slug': this.slug
'.slug': this.blogPost.slug
})
}
}
`

The name passed references $NAME portions of targets from the current
router on down — so comments.name is interpreted as "pull the comments
target from this router, and the name target from that target".

If parameter names are repeated in the desired route, they can be made more
specific by adding $name.$paramName — that is, the full route of $NAMEs to
the desired target, followed by the desired parameter name to fill in.
Otherwise, if parameter names are not repeated, the parameter name itself can
be used without further specification.

-------------

#### reverse.param(name: String, validator: Validator, consume: String) → Parameter

* Validator : Function(String) → Any
* Validator : RegExp
* Validator : Joi

Parameter objects do additional checking on potential matches. All values
matching /[\/]+/ are forwarded to a parameter included in a route. The
parameter's validator is executed on the route.

If the validator is a function the value it returns is included in the
context as the parameter's name. Exceptions are treated as a "did not match"
condition.

If the validator is a [joi][joi] instance, any errors will be treated as "did
not match". It's advisable to always specify .required() on these objects.
The value returned will be the cooked value returned by joi.

If the validator is a RegExp, the value will always be a string. These
regexen should always begin with ^ and end with $ to ensure a full match.

consume is a string containing regex source that controls how the parameter
consumes characters from the incoming path. If not given, it will default to
([^\/]+), which will give the parameter the behavior of matching between /
segments.

If, for example, you'd like to match an entire path including / characters,
you could write:

`javascript
// we use String here to map the input to the output without any transform
reverse.param('path', String, '(.+)')
``

-------------

License

MIT

[node-methods]: https://nodejs.org/api/http.html#http_http_methods
[domain-specific-language]: https://en.wikipedia.org/wiki/Domain-specific_language
[docs-api-reference]: #api