Telekinesis

A lightweight HTTP client and server for the Loom generation

Telekinesis is a lightweight HTTP client for sending and HTTP requests.

Features

• immutable API optimized for Scala 3 and lightweight concurrency with Loom
• Simple and flexible request handling
• HTTP server can be run standalone or wrap a servlet container
• typesafe representations of HTTP request and response headers and MIME types
• transparent typeclass-based request body query parameter serialization and deserialization
• optional pattern-matching on requests
• fast streaming without complexity
• safe parameter and header access
• typesafe representation of URLs

Availability Plan

Telekinesis has not yet been published. The medium-term plan is to build Telekinesis with Fury and to publish it as a source build on Vent. This will enable ordinary users to write and build software which depends on Telekinesis.

Subsequently, Telekinesis will also be made available as a binary in the Maven Central repository. This will enable users of other build tools to use it.

For the overeager, curious and impatient, see building.

Getting Started

Here is an example of a simple HTTP request:

import telekinesis.*

val response = url"http://example.com/test".query(flag = t"yes", param = t"7").get().as[Text]

Sending an HTTP request

An HTTP request may be sent by calling one of the HTTP methods—get, post, put, options, head, trace, delete, connect or patch—on the Http object. As a minimum, these methods all take a URL as their first parameter. This may be provided as a Url (see below) or a Text, or any type which has a contextual ToLocation instance which can convert it into URL string. This may be useful for integration with alternitave URL representations.

If the request is successful, a response will be returned synchronously as an HttpResponse instance. HttpResponse provides the methods status (the HTTP status code), headers (a map of HTTP response headers), and body which will be a representation of the response body, in bytes.

The easiest way to access the body is by converting it to another type, using a contextual reader. That can be achieved by calling as with an appropriate type, for example,

url"https://example.com/service".get().as[Text]

or with a suitable JSON library such as Jacinta,

import jacinta.*
url"http://example.com/file".post(content).as[Json]

Request and response bodies

The type of body is Body, defined as an alias for, Unit | IArray[Byte] | LazyList[IArray[Byte]], a union type corresponding to the cases of an empty response, a response of known length, and a streamed response, respectively.

This type is commonly used for both requests and responses.

Error handling

HTTP requests may fail for a variety of reasons. These will be thrown as HttpErrors only when the as method is invoked (an HttpResponse is always returned from get or post, even in the event of a failure status). An HttpError contains a status field of the HTTP status code.

Some HTTP requests will fail, but will still send a useful response body which can be read and interpreted like any other, albeit from the HttpError instance.

Here is an example of an HTTP error being handled:

try uri.get().as[Text]
catch
  case error@HttpError(HttpStatus.NotFound, _) =>
    t"The page was not found. The server responded with: ${error.as[Text]}"
  case HttpError(_, _) =>
    t"The request failed"

Status

Telekinesis is classified as fledgling. For reference, Soundness projects are categorized into one of the following five stability levels:

• embryonic: for experimental or demonstrative purposes only, without any guarantees of longevity
• fledgling: of proven utility, seeking contributions, but liable to significant redesigns
• maturescent: major design decisions broady settled, seeking probatory adoption and refinement
• dependable: production-ready, subject to controlled ongoing maintenance and enhancement; tagged as version 1.0.0 or later
• adamantine: proven, reliable and production-ready, with no further breaking changes ever anticipated

Projects at any stability level, even embryonic projects, can still be used, as long as caution is taken to avoid a mismatch between the project's stability level and the required stability and maintainability of your own project.

Telekinesis is designed to be small. Its entire source code currently consists of 540 lines of code.

Building

Telekinesis will ultimately be built by Fury, when it is published. In the meantime, two possibilities are offered, however they are acknowledged to be fragile, inadequately tested, and unsuitable for anything more than experimentation. They are provided only for the necessity of providing some answer to the question, "how can I try Telekinesis?".

1. Copy the sources into your own project

   Read the fury file in the repository root to understand Telekinesis's build structure, dependencies and source location; the file format should be short and quite intuitive. Copy the sources into a source directory in your own project, then repeat (recursively) for each of the dependencies.

   The sources are compiled against the latest nightly release of Scala 3. There should be no problem to compile the project together with all of its dependencies in a single compilation.

2. Build with Wrath

   Wrath is a bootstrapping script for building Telekinesis and other projects in the absence of a fully-featured build tool. It is designed to read the fury file in the project directory, and produce a collection of JAR files which can be added to a classpath, by compiling the project and all of its dependencies, including the Scala compiler itself.

   Download the latest version of wrath, make it executable, and add it to your path, for example by copying it to /usr/local/bin/.

   Clone this repository inside an empty directory, so that the build can safely make clones of repositories it depends on as peers of telekinesis. Run wrath -F in the repository root. This will download and compile the latest version of Scala, as well as all of Telekinesis's dependencies.

   If the build was successful, the compiled JAR files can be found in the .wrath/dist directory.

Contributing

Contributors to Telekinesis are welcome and encouraged. New contributors may like to look for issues marked beginner.

We suggest that all contributors read the Contributing Guide to make the process of contributing to Telekinesis easier.

Please do not contact project maintainers privately with questions unless there is a good reason to keep them private. While it can be tempting to repsond to such questions, private answers cannot be shared with a wider audience, and it can result in duplication of effort.

Author

Telekinesis was designed and developed by Jon Pretty, and commercial support and training on all aspects of Scala 3 is available from Propensive OÜ.

Name

The library provides a way of handling URIs, performing "action at a distance", or telekinesis; specifically the processing of a request on a remote server. A man called Uri was also famed for his ability to perform telekinesis with spoons.

In general, Soundness project names are always chosen with some rationale, however it is usually frivolous. Each name is chosen for more for its uniqueness and intrigue than its concision or catchiness, and there is no bias towards names with positive or "nice" meanings—since many of the libraries perform some quite unpleasant tasks.

Names should be English words, though many are obscure or archaic, and it should be noted how willingly English adopts foreign words. Names are generally of Greek or Latin origin, and have often arrived in English via a romance language.

Logo

The logo shows the characters ://, which form part of every URL.

License

Telekinesis is copyright © 2024 Jon Pretty & Propensive OÜ, and is made available under the Apache 2.0 License.