Swagger 2 router

![Build
Status](https://travis-ci.org/wikimedia/swagger-router)

Features

- O(path element) lookup complexity, monomorphic design with simple fast path.
- Support for prefix-based 'mounting' of swagger specs. Example: Mount the
same spec fragments at /en.wikipedia.org/v1/ and
/de.wikipedia.org/v1/.
- Support for capture of fixed path segments. Example:
/{domain:en.wikipedia.org}/v1/. This feature is especially useful in
prefixes, as it enables the consistent construction of sensible params.
- Support for static (purely spec-based) listings. Matching requests ending on
a slash are passed an array of matching child paths in the spec in the
_ls parameter.

Installation

npm install swagger-router

Usage

``javascript
var Router = require('swagger-router');
var router = new Router();

// The main requirement is that each spec has a 'paths' member with some URL
// patterns
var swaggerSpec = {
paths: {
'/': {
get: {
hello: 'A listing'
}
},
'/some/{name}': { // This object is returned as 'value'
get: {
hello: 'world'
}
}
}
};

router.addSpec(swaggerSpec);

// Perform some lookups
console.log(router.lookup('/some/title'));
/*
{
params: {
name: 'title'
},
value: { get: { hello: 'world' } }
}
*/

// Use arrays internally for speed (no escaping / parsing)
router.lookup(['some','path']);

// Trailing slashes set an additional _ls param:
router.lookup(['']); // equivalent: router.lookup('/');
/*
{
params: {
_ls: ['some'],
name: 'title'
},
value: { get: { hello: 'A listing' } }
}
*/

`


URI templating

URIs are represented by URI class, which supports a limited set of features
from URI Template RFC 6570.

$3


- Simple string expression {pattern} - on expansion, looks up a variable named pattern in params
and substitutes its pct-encoded value. On matching, matches a single element in the path, and
sets params.pattern to the path element value.
- Restricted expression {+pattern} - on expansion, works the same way as simple expression, but doesn't
pct-encode reserved characters and ptc-triplets.
On matching, matches the whole subpath and writes it's value to params.pattern variable.
- Optional expression {/pattern} - works the same way as simple expression, but on matching the path
element is optional.
- Fixed expression {pattern:value} - on matching, matches only uris with path element equal to value,
and exports value as params.pattern variable. On expansion, substitutes value.

These features are optimised and available with URI.expand(params) method. Additional features
are available with request templating.

Request templating

Module exports an efficient templating library under Template class.

Example usage:
`javascript
var template = new Template({
method: 'put',
uri: '/{domain}/{$.request.headers.location}',
headers: '{$$.merge($.request.headers, {"additional_name": "additional_value"})}'
body: {
field_from_req_body: '{field_name}',
global_reference: '{$.request.headers.header_name}',
field_with_default_value: '{$$.default($.request.params.param_name, "defaultValue")}'
}
});
var request = template.expand({
request: req,
additional_context: context
});
`

Expressions wrapped in curly braces are considered templates, which are resolved to values
on template expansion. In case some value cannot be resolved, template is expanded to undefined.

$ references global context (object, passed to the expand method). It can contain arbitrary number of objects,
but it must at least contain a request property with an original request.

Short notations are supported, which are resolved to fields of a request part, for example,
'{field_name}' in template body would be resolved to '{$.request.body.field_name}'.
Short notations in uri would be resolved to $.request.params.

Braced syntax is supported, so it's possible to write templates like '{$.request.body[$.request.params.some_field]}'.

Several utility methods are supported:
- $$.default(template, defaultValue) - if template is resolved, use it's value, otherwise use defaultValue.
- $$.merge(template1, template2) - both templates should be evaluated to objects. The result is an object
with merged properties, but without overriding.
- $$.strip(object, properties) - removes field names listed in properties array from an object. properties`
could also be a string, if a single field should be removed.