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haslett

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A lightweight WebSocket library for ClojureScript

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# Haslett [![Build Status](https://github.com/weavejester/haslett/actions/workflows/test.yml/badge.svg)](https://github.com/weavejester/haslett/actions/workflows/test.yml)

A lightweight WebSocket library for ClojureScript that uses
[core.async][].

[core.async]: https://github.com/clojure/core.async

## Installation

Add the following dependency to your deps.edn file:

haslett/haslett {:mvn/version "0.2.0"}

Or to your Leiningen project file:

[haslett "0.2.0"]

## Usage

Haslett provides a simple and idiomatic interface to using WebSockets:

```clojure
(ns example.core
  (:require [cljs.core.async :as a :refer [<! >! go]]
            [haslett.client :as ws]
            [haslett.format :as fmt]))

(go (let [stream (<! (ws/connect "ws://echo.websocket.org"))]
      (>! (:out stream) "Hello World")
      (js/console.log (<! (:in stream)))
      (ws/close stream)))
```

The `connect` function returns a promise channel that produces a map
with four keys: `:socket`, `:close-status`, `:in` and `:out`.

* `:socket` contains the JavaScript `WebSocket` object, in case you need
to access it directly.

* `:close-status` contains a promise channel that a status map is
delivered to when the socket is closed. The status map will provide a
`:code` and `:reason` keys that will explain why the socket was
closed.

* `:in` is a core.async channel to read from.

* `:out` is a core.async channel to write to.

By default, Haslett sends raw strings, but we can change that by
supplying a formatter. Haslett includes formatters for JSON, edn and
Transit:

```clojure
(go (let [stream (<! (ws/connect "ws://echo.websocket.org" {:format fmt/transit}))]
      (>! (:out stream) {:foo [1 2 3]})
      (js/console.log (pr-str (<! (:in stream))))
      (ws/close stream)))
```

You can customize the behaviour further by supplying your own channels
for the source and sink. This allows you to tune the channel buffer,
and add transducers:

```clojure
(ws/connect "ws://echo.websocket.org"
            {:in  (a/chan 10)
             :out (a/chan 10)})
```

When the WebSocket is closed, the `:out` and `:in` channels are
also closed. In addition, a final status map will be delivered to a
promise channel held in the `:close-status` key on the stream.

## License

Distributed under the Eclipse Public License either version 1.0 or (at
your option) any later version.

haslett

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