# lanes

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*A slightly more general HTTP routing library than LFE's lfest*

## Introduction

The lanes project aims to offer some of the YAWS-specific features of the [lfest project]( to a wider selection of BEAM-based web servers. This is done with the understanding that the original design of lfest (and thus the design inherited in the lanes project) is not optimal. For more on the potential end-state for routes and request/response handling in LFE web applications, see the [lrootes project](

For now, though, we are focused on the immediate and practical needs of LFE application developers.

## Dependencies

* Erlang 19+
* `rebar3`

## Usage

Create your application/service routes with the ``(defroutes ...)`` form.
Here is an example that is compatible with [Elli](

(include-lib "lanes-elli/include/macros.lfe")

  ;; This macro generates the handle/3 function used by handle/2.
  ;; top-level
  ('GET #"/"
        (lanes.elli.response:ok "Welcome to the Volvo Store!"))
  ;; single order operations
  ('POST #"/order"
         (lanes-elli-data:create-order (lanes.elli:get-data req))
  ('GET #"/order/:id"
         (lanes-elli-data:get-order id)))
  ('PUT #"/order/:id"
        (lanes-elli-data:update-order id (lanes.elli:get-data req))
  ('DELETE #"/order/:id"
           (lanes-elli-data:delete-order id))
  ;; order collection operations
  ('GET #"/orders"
  ;; payment operations
  ('GET #"/payment/order/:id"
         (lanes-elli-data:get-payment-status id)))
  ('PUT #"/payment/order/:id"
        (lanes-elli-data:make-payment id (lanes.elli:get-data req))
  ;; error conditions
   (lanes.elli.response:not-found "Bad path: invalid operation.")))

For full context, be sure to see the code in `./examples`.

### Consuming Routes

#### Cowboy


#### Elli

The Elli `lanes` plugin supports a `defroutes` macro that generates a
`hanlder/3` function typically used in Elli handler modules. One still
needs to provide the `handle/2` and `handle_event/3` functions in the
module where `defroutes` is called.

#### Nova


#### YAWS

The YAWS `lanes` plugin creates a `routes/3` function which can then
be called in the `out/1` function that is required of a
[YAWS appmod]( module.
For an example of this in action, see
[this mini REST-api](

A few important things to note here:) 

* Each route is composed of an HTTP verb, a path, and a function to execute
  should both the verb and path match.
* The function call in the route has access to the `arg-data` passed from
  YAWS; this contains all the data you could conceivably need to process a
  request. (You may need to import the `yaws_api.hrl` in your module to
  parse the data of your choice, though.)
* If a path has a segment preceded by a colon, this will be converted to a
  variable by the `(defroutes ...)` macro; the variable will then be
  accessible from the function you provide in that route.
* The `(defroutes ...)` macro generates the `routes/3` function; it's
  three arguments are the HTTP verb (method name), the path info (a list of
  path segments, with the `":varname"` segments converted to`varname`/
  variable segments), and then the `arg-data` variable from YAWS.

More details:

lanes needs to provide YAWS with an `out/1` function. The location of this
function is configured in your `etc/yaws.conf` file in the
`<appmods ...>` directives (it can be repeated for supporting multiple

YAWS will call this function with one argument: the YAWS `arg` record
data. Since this function is the entry point for applications running under
YAWS, it is responsible for determining how to process all requests.

The `out/1` function in lane+YAWS-based apps calls the `routes/3` function
generated by the `(defroutes ...)` lanes/YAWS mamcro.

When a lanes-based project is compiled, the `routes/3` function is available for use via
whatever modules have defined routes with `defroutes`.

## License [&#x219F;](#contents)

Apache Version 2 License

Copyright © 2014-2021, Duncan McGreggor <>

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