KnowSheet-REPL

A Read-Eval-Print-Loop (REPL) shell to demonstrate the KnowSheet Bricks C++ syntax.

Installation

Node.js v0.12.0 is required to install and run the REPL.

git clone https://github.com/KnowSheet/KnowSheet-REPL.git
cd KnowSheet-REPL
npm install

Usage

Start the interactive REPL

node run

The command prompt KnowSheet> will appear.

Evaluate from the command-line

echo 'HTTP(GET("http://httpbin.org/get?query=1")).body' | node run

If stdin is not a tty, the REPL starts in a non-interactive mode.

Evaluate and pass the result to another command

echo 'HTTP(GET("http://httpbin.org/get?query=1")).body' | node run | cat

If stdout is not a tty, the result is emitted as text into stdout, the errors are emitted as text into stderr.

Override the default prompt

node run --prompt 'Bricks> '

The command prompt Bricks> will appear.

HTTP client

Bricks provides utilities to perform HTTP requests. By default, redirects are forbidden and result in an error; they can be enabled per request.

Perform an HTTP GET request

KnowSheet> HTTP(GET("http://httpbin.org/get?query=1")).body

Perform an HTTP POST request

KnowSheet> HTTP(POST("http://httpbin.org/post", "BODY", "text/plain")).body

Allow redirects

KnowSheet> HTTP(GET("http://httpbin.org/redirect/5").AllowRedirects()).body

Provide a custom User-Agent

KnowSheet> HTTP(GET("http://httpbin.org/get").UserAgent("KnowSheet-REPL/1.0.0")).body

Provide extra HTTP headers

For GET requests:

KnowSheet> HTTP(GET("http://httpbin.org/get?query=1", HTTPHeaders().Set("Custom", "Header"))).body

For POST requests:

KnowSheet> HTTP(POST("http://httpbin.org/post", "BODY", "text/plain", HTTPHeaders().Set("Custom", "Header"))).body

HTTP server

Bricks provides utilities to create simple HTTP-based servers.

Start an HTTP server

KnowSheet> HTTP(2015)
// KnowSheet Bricks HTTPServer at port 2015

• Bricks maintains a single server per port. No need to explicitly start a server: the first call to HTTP with a port number starts a server on that port and returns an instance of the server; the next calls with the same port reference the started server.
• The calls to the server methods can be chained (each method returns the server instance).
• Each server accepts connections since its start till the process exits. No need to explicitly stop it.

Register an endpoint on an HTTP server

KnowSheet> HTTP(2015).Register("/ping", [](Request r) { r("pong"); })
// KnowSheet Bricks HTTPServer at port 2015
KnowSheet> HTTP(GET("http://localhost:2015/ping")).body
--------------------------------------------------------------------------------
pong
--------------------------------------------------------------------------------
(32ms)

• There can only be a single handler for an endpoint path. The handler is expected to dispatch by HTTP method (verb).
• The handler lambda syntax in the REPL mimics C++11 to a certain extent -- no full lambda support is guaranteed.

Unregister an endpoint from an HTTP server

KnowSheet> HTTP(2015).UnRegister("/ping")

Use the request data in an HTTP server handler

KnowSheet> HTTP(2015).Register("/test", [](Request r){ r(r.timestamp + " " + r.method + " " + r.url.ComposeURL() + "\n" + r.body); })
// KnowSheet Bricks HTTPServer at port 2015
KnowSheet> HTTP(POST("localhost:2015/test", "BODY")).body
--------------------------------------------------------------------------------
1426024237701 POST /test
BODY
--------------------------------------------------------------------------------
(12ms)

JSON

Bricks provides utilities to parse JSON strings into instances of serializable types and serialize them back into JSON. The REPL mimics Bricks C++ syntax to a certain extent.

POST a JSON-encoded instance of a serializable type

KnowSheet> HTTP(POST("http://httpbin.org/post", DemoObject())).body

The syntax mimics C++ Bricks exactly, as long as DemoObject is defined as a serializable type.

Parse a JSON response into an object

KnowSheet> ParseJSON(HTTP(GET("http://httpbin.org/get?query=1")).body).args

The syntax deviates from C++ Bricks which requires a serializable type specified for the response object, for example, auto response = ParseJSON<HttpbinGetResponse>(response_text); or HttpbinGetResponse response; ParseJSON(response_text, response);.

Advanced examples

Chain requests

KnowSheet> ParseJSON(HTTP(POST("http://httpbin.org/post", ParseJSON(HTTP(GET("http://httpbin.org/get?query=1")).body))).body)

In C++ Bricks, the calls to ParseJSON would be templated by serializable types of the response objects, for example, ParseJSON<HttpbinPostResponse>( /* ... */ ).