https://github.com/marcinzh/enterprise

Serve HTTP using Algebraic Effects and Handlers
https://github.com/marcinzh/enterprise

algebraic-effects functional-programming http-server scala

Last synced: 13 days ago
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Serve HTTP using Algebraic Effects and Handlers

• Host: GitHub
• URL: https://github.com/marcinzh/enterprise
• Owner: marcinzh
• License: mit
• Created: 2023-07-25T20:20:08.000Z (over 2 years ago)
• Default Branch: master
• Last Pushed: 2025-08-07T10:50:32.000Z (8 months ago)
• Last Synced: 2025-08-07T11:14:13.140Z (8 months ago)
• Topics: algebraic-effects, functional-programming, http-server, scala
• Language: Scala
• Homepage:
• Size: 79.1 KB
• Stars: 6
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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# Enterprise 

Minimalist library for creating HTTP services, using algebraic effects and handlers.

- ⚗️ 🔬 🧪   𝑷𝑹𝑶𝑻𝑶𝑻𝒀𝑷𝑬     🚧 WIP 🚧

- Uses Scala 3.

- Uses [Turbolift](https://marcinzh.github.io/turbolift/) as effect system.

- Adapts parts of design of preexisting purely-functional HTTP libraries ([Http4s](https://github.com/http4s/http4s), [ZIO-Http](https://github.com/zio/zio-http)) for the new effect system.

## Design

Services are defined as values of type:

```scala

type Service[U] = Response[U] !! (RequestEffect & U)

````

Which should be read as: "Computation, that **returns** `Response` and **requests effects**: `RequestEffect` and `U`".

Where `U` means user selected set of effects involved in computing the response.

`RequestEffect` is an instance of Turbolift's `Reader` effect, predefined in Enterprise.

Examples of ptional effects, predefined in Enterprise, are:

- `ResponseError` - An instance of Turbolift's `Error` effect. Allows interruption of processing of the request, returning given `Response` value. 

- `RouterEffect` - An instance of Turbolift's `Choice` effect. Allows defining routes by partial functions. Composition can be done with Turbolift's `++!` operator (similar to `<|>` of `Alternative`).

Such effects can be handled at:

- Request scope: before `.serve` call (i.e. once per each served request). 

- Server scope: after `.serve` call (i.e. once per server launch).

Multiple handlers can be chained, using Turbolift's `&&&!` operator.

## Example

Run the server with `scala-cli`:

> [!IMPORTANT]

> Turbolift requires **Java 11** or newer.

```scala

//> using scala "3.3.7"

//> using dep "io.github.marcinzh::enterprise-core:0.12.0"

package examples

import turbolift.!!

import turbolift.Extensions._

import enterprise.{Response, Router}

import enterprise.DSL._

import enterprise.server.Syntax._

import enterprise.server.undertow.UndertowServer

@main def main =

  Router:

    case GET / "sarcastic" / text =>

      val text2 = text.zipWithIndex.map((c, i) => if i % 2 == 0 then c.toLower else c.toUpper).mkString

      Response.text(text2).pure_!!

  .handleWith(Router.handler)

  .serve

  .handleWith(UndertowServer.handler)

  .handleWith(Config.localhost(9000).handler)

  .runIO

```

Query the server with `HTTPie`:

```bash

http GET "http://localhost:9000/sarcastic/Resistance is futile"

```

---

See [examples folder](./modules/examples/src/main/scala/examples/) for more.