### Invoking a Ring Adapter to Start an HTTP Server in Clojure

Source: https://github.com/ring-clojure/ring/blob/master/SPEC.md

This code demonstrates how to invoke a Ring adapter. An adapter is a side-effectful function that takes a `handler` function and an `options` map, then starts an HTTP server. It processes incoming requests, converts them to request maps, passes them to the handler, and sends the handler's response back to the client.

```Clojure
(run-adapter handler options)
```

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

### Running Ring Adapter in Asynchronous Mode

Source: https://github.com/ring-clojure/ring/blob/master/SPEC.md

This example shows how to invoke a Ring adapter, such as `run-adapter`, with an option to specify asynchronous behavior. The `:async? true` option indicates that the adapter should use the asynchronous handler API.

```Clojure
(run-adapter handler {:async? true})
```

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

### Defining Ring Websocket PingListener Protocol

Source: https://github.com/ring-clojure/ring/blob/master/SPEC.md

This optional protocol defines the `on-ping` callback for a websocket listener. If implemented, the user is responsible for sending the corresponding 'pong' message. If not implemented, the adapter will automatically respond to ping messages with a pong.

```Clojure
(defprotocol PingListener
  (on-ping [listener socket data]))
```

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

### Adding Ring Core Dependency to deps.edn (Clojure)

Source: https://github.com/ring-clojure/ring/blob/master/README.md

This snippet shows how to add the `ring-core` library as a dependency to a Clojure project using `deps.edn`. It specifies the library group and artifact ID, along with its Maven version. This allows the project to use Ring's core functions and middleware.

```Clojure
ring/ring-core {:mvn/version "1.14.1"}
```

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

### Adding Ring Core Dependency to Leiningen (Clojure)

Source: https://github.com/ring-clojure/ring/blob/master/README.md

This snippet demonstrates how to declare the `ring-core` library as a dependency in a Leiningen project file. It includes the library's group, artifact ID, and version, enabling the project to utilize Ring's core functionalities.

```Clojure
[ring/ring-core "1.14.1"]
```

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

### Defining Ring Websocket Listener Protocol

Source: https://github.com/ring-clojure/ring/blob/master/SPEC.md

This protocol defines the essential callbacks for a Ring websocket listener. It includes functions for handling websocket events such as opening (`on-open`), receiving messages (`on-message`), errors (`on-error`), and closing (`on-close`). The `on-pong` callback is also part of this protocol.

```Clojure
(defprotocol Listener
  (on-open    [listener socket])
  (on-message [listener socket message])
  (on-pong    [listener socket data])
  (on-error   [listener socket throwable])
  (on-close   [listener socket code reason]))
```

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

### Asynchronous Ring Handler - Exception Handling

Source: https://github.com/ring-clojure/ring/blob/master/SPEC.md

This asynchronous handler function illustrates how to handle and raise an exception. It takes a `request` map, a `respond` callback, and a `raise` callback. The `raise` function is invoked with the `exception` object to signal an error.

```Clojure
(fn [request respond raise]
  (raise exception))
```

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

### Returning Websocket Response from Asynchronous Handler

Source: https://github.com/ring-clojure/ring/blob/master/SPEC.md

This asynchronous Ring handler shows how to send a websocket response using the `respond` callback. Similar to the synchronous version, it provides a map with the `:ring.websocket/listener` key, indicating a websocket upgrade.

```Clojure
(fn [request respond raise]
  (respond #:ring.websocket{:listener websocket-listener}))
```

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

### Ring Handler Supporting Synchronous and Asynchronous Behavior

Source: https://github.com/ring-clojure/ring/blob/master/SPEC.md

This handler function demonstrates how to support both synchronous and asynchronous API calls by defining multiple arities. The single-argument arity handles synchronous requests, while the three-argument arity handles asynchronous requests by invoking the `respond` callback.

```Clojure
(fn
  ([request]
    response)
  ([request respond raise]
    (respond response)))
```

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

### Asynchronous Ring Handler - Successful Response

Source: https://github.com/ring-clojure/ring/blob/master/SPEC.md

This asynchronous handler function demonstrates how to send a successful HTTP response. It takes a `request` map, a `respond` callback for sending the response, and a `raise` callback for exceptions. The `respond` function is invoked with the `response` map.

```Clojure
(fn [request respond raise]
  (respond response))
```

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

### Returning Websocket Response from Synchronous Handler

Source: https://github.com/ring-clojure/ring/blob/master/SPEC.md

This synchronous Ring handler demonstrates how to return a websocket response instead of a standard HTTP response. It constructs a map with the `:ring.websocket/listener` key, which must satisfy the `ring.websocket/Listener` protocol.

```Clojure
(fn [request]
  #:ring.websocket{:listener websocket-listener})
```

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

### Defining the Ring Clojure Websocket AsyncSocket Protocol

Source: https://github.com/ring-clojure/ring/blob/master/SPEC.md

This Clojure code defines the `ring.websocket.protocols/AsyncSocket` protocol, an optional extension for websocket sockets in Ring. It provides an asynchronous method for sending messages, allowing for non-blocking operations and callback functions for success and failure, which is useful for performance-critical applications.

```Clojure
(defprotocol AsyncSocket
  (-send-async [socket message succeed fail]))
```

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

### Defining the Ring Clojure Websocket Socket Protocol

Source: https://github.com/ring-clojure/ring/blob/master/SPEC.md

This Clojure code defines the `ring.websocket.protocols/Socket` protocol, which is mandatory for any object acting as a websocket socket in Ring. It specifies the fundamental operations for managing a websocket connection, including checking its open status, sending messages, sending ping/pong frames, and closing the connection with a specific code and reason.

```Clojure
(defprotocol Socket
  (-open? [socket])
  (-send  [socket message])
  (-ping  [socket data])
  (-pong  [socket data])
  (-close [socket code reason]))
```

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

### Defining a Synchronous Ring Handler in Clojure

Source: https://github.com/ring-clojure/ring/blob/master/SPEC.md

This snippet illustrates the basic structure of a synchronous Ring handler. A handler is a Clojure function that accepts a single `request` map as an argument and is expected to return a `response` map, forming the core logic of a web application.

```Clojure
(fn [request] response)
```

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

### Defining StreamableResponseBody Protocol in Ring

Source: https://github.com/ring-clojure/ring/blob/master/SPEC.md

This protocol defines the interface for response bodies that can be streamed to an output stream. It specifies the `write-body-to-stream` function, which takes the body, response, and output stream as arguments to write the body content.

```Clojure
(defprotocol StreamableResponseBody
  (write-body-to-stream [body response output-stream]))
```

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