gurl

ᵍ🆄🆁🅻

Combinator library for network I/O

A pure functional style to express communication behavior by hiding the networking complexity using combinators. This construction decorates http i/o pipeline(s) with "programmable commas", allowing to make http requests with few interesting properties such as composition and laziness.

User Guide | Playground | Examples | API Specification

Inspiration

Microservices have become a design style to evolve system architecture in parallel, implement stable and consistent interfaces. An expressive language is required to design the variety of network communication use-cases. Pure functional languages fit very well to express communication behavior. These languages give rich abstractions to hide the networking complexity using monads. The IO-monads help us to compose a chain of network operations and represent them as pure computation, building new things from small reusable elements. This library is implemented after Erlang's m_http

The library attempts to adapt a human-friendly logging syntax of HTTP I/O used by curl and Behavior as a Code paradigm. It connects cause-and-effect (Given/When/Then) with the networking (Input/Process/Output).

> GET / HTTP/1.1
> Host: example.com
> User-Agent: curl/7.54.0
> Accept: application/json
>
< HTTP/1.1 200 OK
< Content-Type: text/html; charset=UTF-8
< Server: ECS (phd/FD58)
< ...

This semantic provides an intuitive approach to specify HTTP requests and expected responses. Adoption of this syntax as Go native code provides a rich capabilities for network programming.

Key features

Standard Golang packages implement a low-level HTTP interface, which requires knowledge about the protocol itself, understanding of Golang implementation aspects, and a bit of boilerplate coding. It also misses standardized chaining (composition) of individual requests. ᵍ🆄🆁🅻 inherits an ability of pure functional languages to express communication behavior by hiding the networking complexity using combinators (sometimes it is called category pattern). Combinators make a chain of network operations as a pure computation.

• cause-and-effect abstraction of HTTP I/O using Golang naive do-notation
• lazy composition of individual HTTP requests to complex networking computations
• human-friendly, Go native and declarative syntax to depict HTTP operations
• implements a declarative approach for testing of RESTful interfaces
• automatically encodes/decodes Golang native HTTP payload using Content-Type hints
• supports generic transformation to algebraic data types
• simplifies error handling with naive Either implementation

Getting started

The library requires Go 1.13 or later

The latest version of the library is available at its master branch. All development, including new features and bug fixes, take place on the master branch using forking and pull requests as described in contribution guidelines.

The following code snippet demonstrates a typical usage scenario. See runnable http request example.

import (
  "github.com/fogfish/gurl"
  "github.com/fogfish/gurl/http"
  ø "github.com/fogfish/gurl/http/send"
  ƒ "github.com/fogfish/gurl/http/recv"
)

// You can declare any types and use them as part of networking I/O.
type Payload struct {
  Origin string `json:"origin"`
  Url    string `json:"url"`
}

// the variable holds results of network I/O
var data Payload

// lazy HTTP I/O specification
var lazy := http.Join(
  // declare HTTP request
  ø.GET.URL("http://httpbin.org/get"),
  ø.Accept.JSON,

  // declare HTTP response and "recv" JSON to the variable
  ƒ.Status.OK,
  ƒ.ContentType.JSON,
  ƒ.Recv(&data),
)

// Note: neither `lazy` or `data` hold the result of HTTP I/O.
//       the code above just builds a composable "promise".
//       it is required to evaluate a side-effect of "HTTP computation".
//       the lazy pipeline is evaluated when HTTP I/O pool is applied over
if lazy(http.DefaultIO()).Fail != nil {
  // error handling
}

Next steps

• Study User Guide if defines library concepts and guides about api usage;
• Play with the library at Golang playground;
• Use examples as a reference for further development.

How To Contribute

The library is MIT licensed and accepts contributions via GitHub pull requests:

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Added some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

The build and testing process requires Go version 1.13 or later.

Build and test the library in your development console.

git clone https://github.com/fogfish/gurl
cd gurl
go test ./...

commit message

The commit message helps us to write a good release note, speed-up review process. The message should address two questions what changed and why. The project follows the template defined by chapter Contributing to a Project of Git book.

Short (50 chars or less) summary of changes

More detailed explanatory text, if necessary. Wrap it to about 72 characters or so. In some contexts, the first line is treated as the subject of an email and the rest of the text as the body. The blank line separating the summary from the body is critical (unless you omit the body entirely); tools like rebase can get confused if you run the two together.

Further paragraphs come after blank lines.

Bullet points are okay, too

Typically a hyphen or asterisk is used for the bullet, preceded by a single space, with blank lines in between, but conventions vary here

bugs

If you experience any issues with the library, please let us know via GitHub issues. We appreciate detailed and accurate reports that help us to identity and replicate the issue.

• Specify the configuration of your environment. Include which operating system you use and the versions of runtime environments.

• Attach logs, screenshots and exceptions, if possible.

• Reveal the steps you took to reproduce the problem, include code snippet or links to your project.

License