Enterprise

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

• ⚗️ 🔬 🧪   𝑷𝑹𝑶𝑻𝑶𝑻𝒀𝑷𝑬   🚧 WIP 🚧
• Uses Scala 3.
• Uses Turbolift as effect system.
• Adapts parts of design of preexisting purely-functional HTTP libraries (Http4s, ZIO-Http) for the new effect system.

Design

Services are defined as values of type:

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:

//> 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:

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

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See examples folder for more.